Warnings: General show spoilers for all 3 seasons. Slightly AU (see note, which itself is a slight spoiler for Season 3).
Word Count: 17,000

Originally written for "The Big Bang Theory" big bang challenge from September 2010…I'm not sure why I never posted it here.

Notes: Penny and Leonard never got together, never even went on the early dates. Most everything else happened, although maybe in a slightly different way.

It starts at the Chancellor's Award ceremony.

Penny's sitting at the table, alternately feeling sorry for Leonard as he's rambling about his failed childhood science project and for herself because she's at a science award dinner with the guys instead of with her girl friends like she usually is on a weekend night. But the food is good and it's free and if she's really honest with herself, it'll be kind of nice seeing Sheldon up on that stage in the awesome suit she picked out for him.

Sheldon's a ball of nerves to her left and while Leonard's talking, she has to put a hand on his arm to keep him from vibrating the dinnerware off the table. The fact that he doesn't flinch is a testament to how nervous he is. Penny moves the wine away from him because, really, she's known all of them long enough to know they're truly lousy drunks. Sheldon's barely tolerable when he's sober much less tipsy.

She's coaching him through the stage fright, distracting him with quiet inane chatter in his ear so he can't think about it while Leonard keeps talking and would he just stop talking about his science project and mother issues already?

Finally, Leonard yields the stage to Sheldon and Penny's quietly proud she doesn't actually have to drag the poor guy up the steps herself. She watches, holding her breath, as he puts his hands on the podium and stares out at the crowd and up into the bright lights.

He's silent for an unnaturally long time and just when Penny thinks he's going to faint, he takes a deep breath and starts talking.

And, really, it's not that bad. Sure, he manages to piss off just about every department at the university including his own, but it's Sheldon and he's also able to begrudgingly thank those who (finally) acknowledged his brilliance (after all this time).

Penny's pretty sure she's imagining hearing the words "think of the science" muttered by a few people sitting at the table behind her. Mostly it's because those are the words going through her mind.

These days, when Sheldon goes off on one of his physics tirades, she really does pay attention. Penny's looked up enough things to have a loose grasp-a very loose grasp-of fundamental physics. Which, of course, doesn't exactly help her when he's talking string theory. But it's a start and it's what she'd wanted and it's what he'd taught her. So she pays attention and she picks up on key words and she really, really could have used this skill in college but anyway.

Sheldon's aware enough to know that his audience, while mostly scientists and those associated with science, aren't physicists and tailors the recounting of his scientific exploits to a slightly lower level than normal. He's the only person Penny knows who can both insult one's intelligence and blow right past the furthest reaches of one's understanding in twenty words or less.

By the end of the night, Penny's mental list of things to look up later is pretty big and she's sure she'll forget half of it by the time they get home. (But that's the beauty of Wikipedia, she knows, since she's stayed up way too late on many nights clicking on all the damn links.)

And while Penny now has a greater appreciation of the sciences and for what the guys do, it's Leonard who really kicks off her thought processes into the weirdest direction they've ever gone.

Leonard's still grumbling about the lima bean project on the ride home and Penny's trying really, really hard not to laugh since she's sitting in the passenger seat-thus, the easiest to see, even if she turns to the window-while he drives. She barely manages and, luckily, Leonard is too preoccupied with driving and his own woes to realize the grimace plastered on her face is really Penny trying desperately not to laugh and not the compassion he so desperately wants.

Other than giving her an excuse to (silently) laugh harder than she has in a really long time, the conversation also starts a thought reaction in her mind and she can't get rid of it.

See, when she was in elementary school, she had to do a science fair. Science wasn't big in the Midwest, but they were trying, so every kid had to do something. Penny remembers going home with the assignment and wailing at her father's knee because she had no idea what to do.

At the time, her relationship with her father was still good. He'd picked her up, thumbed the baseball cap on her head, and said, "Slugger, let me tell you about corn and genetics."

It was one of the best times she'd had with her father and the first time she'd learned about the scientific method and put it to use. She won first prize.

Fast forward a decade or so and Penny doesn't really have a use for the scientific method anymore, but Leonard's nostalgia is poking her in the brain for no discernible reason.

The combination of hanging around the boys for a few years, seeing Sheldon in a really good suit, and generally inhaling science on a daily basis shifts Penny's brain into a different kind of orbit.

She starts having strange dreams. More than once Penny wakes up thinking about whiteboards and bosons and quarks and beakers. She has an inexplicable urge to watch the Muppets those mornings.

She starts thinking of weird projects. Really, they're Sheldon's projects. Penny's watched enough science fiction with the guys that she starts wondering if maybe they really could build that brain scrambling device with the right frequencies and what the hell?

And then one day, it all comes to a head and her brain deposits the most preposterous idea ever: Is homo novus susceptible to romance?

Penny falls out of bed the morning that idea presents itself just as she's waking up. She's laughing so hard at the idea she's surprised she hasn't smacked her head against something. To be honest, she thought she had hit her head to evoke that kind of thought.

It's dumb and it's silly and it's Sheldon but the thought stays.

And it won't leave.

A couple days later, Sheldon realizes there's something going on with Penny. At first he dismisses it, after all she's always been a little bit of a wild card and it's taken years to train himself not to be too perturbed by her sometimes unpredictable behavior. But then he notices...things.

He swears she giggles every time she looks at him.

And, the most disturbing of all, he is almost positive she's staring at him when he's turned away.

This goes on for a couple days before he finally has enough.

Penny is sitting on the couch, flipping through a magazine. Sheldon's pretty sure she's not really reading it but her hands still when he speaks.

"Penny, why do you keep laughing when you look at me?" he blurts.

"What?"

Sheldon furrows his brow. Maybe he's misreading her. Body language isn't his forte, but...

"I'm fairly certain you are laughing at me," he tries again.

They stare for a moment and, just as he suspected, Penny's lips twitch and soon she's grinning at him.

"I'm sorry, Sheldon, I just had a very weird idea about you that came up in a dream a while ago."

She's biting her lip now and he can see her shoulders shake as she tries, and fails, to suppress more laughter. He frowns further.

"I assure you any nocturnal fantasies involving you and I are no laughing matter," Sheldon admonishes.

And then she's outright laughing, perilously close to leaning on his spot.

"No, no, it's nothing like that," Penny manages, righting her posture. Sheldon tries not to twitch as her hand rests upon his cushion. "Well, not really. I just...had an idea. A question, really."

He frowns at her more and then turns back to his laptop. He has, after all, important work to do.

Right now.

If he can remember what he is working on.

But Penny has distracted him and now he can't concentrate. Sheldon turns back to her.

They stare at each other again and he swears she issues a silent challenge to him with her eyes as one slender eyebrow arches just slightly.

"I admit that my curiosity is piqued," he finally says.

Penny's eyes go up towards the ceiling and off to the right. They stop moving, then, but Sheldon's pretty sure she was going to do a full eye roll. He narrows his eyes when she doesn't respond.

"Tell me."

"I don't know if I want to."

"Very well."

Sheldon turns back to his laptop once more and furiously tries to ignore her. Except he can't because he knows she's staring at him.

A minute ticks by and neither of them speak or move. He doesn't hear the pages of her magazine flip.

Slowly, he turns all the way around in his seat and she is, as he suspected, staring at him.

And then she bursts out laughing.

"Okay, okay. For some reason, my brain decided to ask me if it was possible to seduce homo novus."

It's Sheldon's turn to raise his eyebrows and he's the one staring at her for almost a full minute before he speaks.

"Well, if that's all," he exclaims, relief in his voice. He readjusts his posture into "lecture mode". "Being homo novus, I have some experience in this matter and can say with certainty that the answer is 'no'."

Rather than gaining acceptance for his answer, though, Sheldon is perplexed when Penny makes a face at him. He starts to get a little alarmed when she rises from the couch and approaches him slowly. If he were to apply a metaphor, Sheldon would say Penny is stalking towards him like a tiger with prey in its sights. She stops a few feet in front of him and he visibly relaxes.

"Care to make a wager?" she asks, hands on her hips.

"I beg your pardon?" He stands so she's not looking down at him.

Penny shakes her head and scoffs. "I will bet you, Sheldon Cooper, that homo novus can, indeed, be seduced."

Unconsciously, Sheldon steps back, his arms crossing defensively in front of him.

He is both wary and curious and he berates himself for being drawn into Penny's inane thought. "By what method are you going to use to attempt to prove this preposterous theory of yours?"

Penny chews on her lip for a moment and says, "The scientific method."

He was prepared to dismiss her bet, certain she'd use some brute force method or other unsubstantiated means but this...this was different. This was science.

Sheldon takes a step forward. "What's the wager?"

Penny crosses her arms to match him and also steps forward. "If I win, I get to sit in your spot for a week."

Sheldon moves again, and now they're toe-to-toe. "If I win, you have to drive me wherever I want, whenever I want-outside of your working hours, of course-for a week."

There is silence between them for a long beat.

"Deal."

"Deal."

Penny spins on her heel and stalks out of the apartment, door slamming behind her.

Sheldon, meanwhile, is still standing exactly where he was and, having seen the determination in Penny's eyes, starts having slight misgivings.

Leonard is walking up the steps when Penny steps out of the apartment.

"Oh, hey, Penny," he greets.

"Hey, Leonard," she says as she blows right past him and into her apartment.

Perplexed, Leonard looks after her and stares as she starts throwing items around in her living room. He stands just outside the open front door and observes for a while.

"So...whatcha doin'?" he asks, his curiosity getting the best of him.

"What?" Penny asks, whirling around. "Oh. Nothing. It's stupid. No, you know what? This is perfect!"

She barrels towards him, then, and Leonard takes a step back. Penny grabs his arm and leans in.

"Leonard, I need your help," she pleads. "You're my only hope."

Leonard's face contorts like this: confusion, hope, confusion, mild glee at the Star Wars reference , and back to confusion.

"With what?" he asks slowly.

"You probably know Sheldon the best out of all the guys, right?"

He nods, still not quite understanding where the conversation is going.

"I need you to help me seduce him."

Silence.

If a pin dropped, any noise it made would have been completely absorbed by the sudden vacuum of sound that appears in the room.

"What?"

Penny blinks and then starts laughing and smacks her palm to her forehead.

"Oh! Sorry...sorry. I forgot you weren't there when this all started. Come in, come in. I don't want him to overhear my plans," she explains, tugging him into her apartment and shutting the door.

Leonard is still reeling and he wonders if he's having a nightmare. And it doesn't get better because Penny's trying to explain everything to him and he wonders if somehow she body swapped with Sheldon because he's pretty sure he's never heard Penny even make a fraction of a comment like the string of words she's saying right now that sound a whole lot like one of Sheldon's scientific tirades.

"And he was just so...so...arrogant and...and..."

Leonard's brain finally catches up.

"And so...Sheldon?" he suggests.

"Yes!" Penny exclaims, grabbing onto his arm again. "And you know him the best so you can offer some, I don't know, information or, you know, insight."

He's staring at her now and he starts to squirm under her gaze because she looks so expectant and beautiful and it should make him happy, because, see, Leonard's had this hope that if Penny improved her education and was more interested in science, she would be the absolute perfect girl for him. It's not that she's stupid, far from it, she just has a different set of topics she knows well and that don't really mesh with his interests.

But there's something else going on. Leonard''s used to losing to the non-geek. He's used to having the pretty girl smile over his shoulder to the jock behind him or whatever other stud is in the vicinity. Leonard's height, or lack thereof, never helped in those situations. But this? This is totally different.

Of all the guys Penny could be focused on other than him, it has to be Sheldon. And, if he's perfectly honest with himself, it makes him a little bit mad.

"You want me," Leonard starts, "to help you seduce Sheldon?"

Penny nods, a hopeful smile still on her lips, and Leonard's already trodden heart gets one more footprint-or high heel-in it. He likes to think he's not a bad person but right now he just can't be the good guy.

"No."

Leonard spins on his heel and quietly walks out of Penny's apartment.

Sheldon's not within sight when Leonard enters their apartment and for that he's glad. He's not sure how he would react to Sheldon at that moment.

To be fair, it wasn't the taller physicist's fault. Sheldon was infuriatingly stubborn and often downright crazy (despite protests that he'd been tested to the contrary) but there was something about him that pulled people in. It's as if Sheldon's personal gravitational field overcompensated for the fact that he didn't have any social skills. Thus, when a person is sucked into Sheldon's universe, they tend to stay, whether they want to or not. It's the only reason Leonard can think of for why he's stayed roommates with the man for over 7 years.

Leonard mopes around in the living room for a while before stalking to his bedroom and flopping on his bed. He lays there, glasses askew on his face, for long, quiet minutes. He just can't get over Penny's absurd request. What in the world would possess her to attempt to pursue Sheldon, the most un-pursuable man in the world?

Penny doesn't get any sleep that night. She's disappointed and a little mad at Leonard for not helping her, but she has work to do. After Google searching for a few things and consulting Wikipedia, she compiles a list of supplies and heads off to the 24 hour drug store to get everything she can. The rest will have to wait until the next day but there are certain items she needs immediately.

She also picks up a few more composition notebooks, deciding she needs at least one per phase of the scientific method. Penny doesn't want to screw this up.

As the night turns to morning, she digs through her e-mail from a couple years ago and finds the link to Sheldon's Google calendar. Penny notes the first appointment of the day, does a little mental math, and stuffs some essential items in a Hello Kitty tote bag before grabbing her emergency key and heading to the guys' apartment.

Quietly, she sneaks into the other apartment and into Sheldon's bedroom. There, she carefully extracts her supplies, sets them up to be accessible, then waits.

Sheldon Cooper is a creature of habit. He wakes up at the same time everyday to begin his morning routine. He looks forward to it because, to him, it is a constant.

When Sheldon wakes up this day, he feels comfort in the unalterable routine for approximately 370 milliseconds before it all changes and everything else is shot to hell.

He barely has time to register that his alarm has gone off before a hand is on his chin and a stick is forced into his mouth.

Sheldon struggles, but the grip is strong, and it isn't until his eyes focus on his assailant that he stops moving, mostly out of shock. He's finally able to pull away and he spits out the foreign object in his mouth.

"Penny?"

"Hold still, Sheldon," she admonishes, retrieving the fallen object. It's a thermometer, he sees, and she attempts to redirect it to his mouth.

Sheldon clamps a hand over his mouth and shakes his head.

"Come on, Sheldon, this is for science," she pleads.

He moves his hand away from his mouth just far enough to speak. "It's dirty, now."

Penny huffs and reaches into the bag by her side. She pulls out a small container and shows it to him. It's a box of sterile, disposable thermometer covers.

"Is this really necessary?" Sheldon complains, trying to inch away from her. Unfortunately, he's rather restricted by his covers.

"The second step is observation, Sheldon." She's put a thermometer cover on and is reaching for his face again.

Sheldon frowns. "This is intrusion, Penny. People can't be in my room."

"Science, Sheldon," she reiterates, getting on her knees on his bed and trying to catch his face.

Sheldon manages to squirm out of his covers and scrambles out of bed, backing up to the far corner of his room.

"Sheldon!"

"I fail to see why you must invade my person for your experiment, Penny." His eyes are bouncing around the room fast, looking for an escape route.

Penny is off the bed now and approaching him. Sheldon feels oddly like prey again.

"Well, I need a baseline," she starts, waving the thermometer at him. "Open up!"

He starts to protest again but Penny's hand shoots up and clamps on his chin, forcing his mouth open. She sticks the thermometer in his mouth and shuts his mouth. Sheldon struggles more but Penny's having none of it.

"Just a few seconds, Sheldon, that's all I need for this!"

Sure enough, the thermometer beeps and Penny extracts it, reading the value. She releases him abruptly, hopping back on his bed to root around in her bag. Penny pulls out a notebook and writes something down.

Sheldon is still observing her with trepidation when she finishes and she looks up at him.

"Well?"

"What?"

"I need to take your blood pressure, now," she says, pulling out a blood pressure cuff and stethoscope.

"Absolutely not."

Penny eyes him, then consults her notebook. "One of the signs of physical arousal is a sudden change in blood pressure," she recites. "How am I supposed to know if you have a sudden change in blood pressure if I don't know what your blood pressure is normally?"

Sheldon's mouth moves but no words come out. Clearly, his cognitive functions are not at their best this early in the morning.

"Penny, since you have disrupted my morning routine, any readings you take right now will be worthless."

There. That should do it.

Except it doesn't.

Penny shrugs and points to the bed. "Sit down. I haven't done this before so I need practice anyway."

Sheldon balks, trying to back into the wall.

Penny blinks at him and sets her shoulders. "Don't make me hogtie you."

A beat passes and then Sheldon's shoulders droop. He hangs his head, defeated, and makes his way to the bed, sitting on the edge.

Of course, things still don't go smoothly.

"I don't think that is the proper placement for the sphygmomanometer, Penny."

"The what?"

"… Blood pressure cuff."

"Oh. Well, it would help if you would hold still, Sheldon."

"Ow."

"You're such a baby, I haven't even started."

"I think that is sufficient inflate—OW."

"There! Done!"

"I think you've bruised me, Penny."

Penny, preoccupied with stuffing all of her materials back in her tote bag, levels a look on him.

"If you put up this much of a fight in future measurements, bruises will be the least of your worries, Sheldon."

Before he can respond, she's off his bed, out of his room, and he can hear the slam of the front door.

Rubbing his arm, Sheldon attempts to process what just happened.

The rest of the day goes no better.

Sheldon spends the morning working through some incomplete correlation theorems the international physics community is requesting input on and is tapping a finger on the cap of a dry-erase marker when the door to his office bursts open and Penny bustles in.

"Penny? What are you doing here?"

He quickly moves behind his desk, relatively safe for the moment, while Penny surveys his office.

"Nice place. Midday measurements. I don't think I've seen it before. Let's get started."

Sheldon is momentarily at a loss for words as he attempts to decipher her disconnected thoughts. He jumps when she starts moving around the desk towards him, thermometer in hand. He mirrors her movements, keeping the desk between them.

"Penny, this is completely unacceptable."

"I've already explained this before, Sheldon," she says before trying to outmaneuver him.

Sheldon finds himself cornered, a dry-erase marker his only weapon. For the moment, it keeps her just a little more than an arm's length away as he wields it like a weapon, pressing the cap against her left shoulder.

"No. This time you have gone too far, intruding on my work place."

For a long moment, Sheldon thinks his display of assertion is working until he notices the smile slowly spreading on Penny's features.

With no warning, Penny is suddenly up in his face and Sheldon finds himself craning his neck at an odd angle so as to avoid physical contact.

"Really?" Penny says, but Sheldon notes an odd timbre to her voice and wonders if there's something wrong with her. "And what are you going to do about it?"

He runs through the possible reasons her behavior could have changed and starts to panic. "Are you ill?"

Penny blinks and a look of confusion crosses her features. "What?"

"Your behavior is quite erratic and the change in your voice suggests a physical ailment," Sheldon reasons.

Penny blinks, then steps back, laughing to herself.

"Well, what's this?" a voice oozes from the doorway.

Sheldon frowns when he sees Howard, Raj, and Leonard loitering on the threshold to his office. Howard's eyes are flicking between he and Penny, no doubt thinking up a million fantasies a second. Raj claps a hand over his mouth and then leans over to frantically whisper in Wolowitz's ear. Leonard just stares, agape, the furrow between his eyebrows quickly becoming a full on crevasse.

"An afternoon tryst, perhaps?" Howard suggests, waggling his eyebrows. Raj snickers beside him.

Annoyed, Sheldon opens his mouth to respond, but Penny beats him to it.

"And what if it is?" Penny asks, stalking towards Howard, the thermometer gripped in her hand.

"What? No. Wait. You can't be serious," he blabbers, flustered.

"Don't be ridiculous," Sheldon breaks into the conversation, voice a couple octaves higher than he'd intended. "Penny was just leaving."

"Not until I get my measurements," she protests, pointing the thermometer at him.

"Measurements, hmm?" Howard drawls. He saunters into the office, his hips thrusting forward suggestively. "You can measure me anytime."

Penny narrows her eyes and turns to face Howard, the thermometer still pointing at Sheldon.

"Sheldon, put this in your mouth now before I decide to stick it somewhere else for a reading."

She lets go of the thermometer and Sheldon is slightly amazed to find that he's actually taken it from her. He puts the offending item, with a new sterile cover on it, into his mouth while Penny stalks towards Wolowitz.

"For your information," Penny says, pointing a finger at Howard but stopping short of actually touching him, "I am conducting a serious experiment here."

"Hey, hey," he says, backpedaling both literally and figuratively. "I was just kidding. And, in any case, what experi-"

Wolowitz's reply is cut short by the door slamming in his face, a shocked Raj and Leonard witnessing the whole ordeal.

Sheldon's ready when Penny turns around. He holds a piece of paper in front of her face. While she was dealing with Wolowitz, he'd had time not only to take his temperature but his blood pressure as well.

"What? Oh! Thanks!"

She's beaming up at him now and for a brief moment, Sheldon is taken aback by her quick mood shift.

"What were they doing here anyway?" she asks, digging through her bag and pulling out a notebook.

Sheldon steps back, processing. "It's lunch time."

"Hmm," Penny muses. She looks up at him them, a strange smile on her face. "Your blood pressure is up from this morning."

Sheldon narrows his eyes. "An anomaly, I assure you. Having you burst into my work place like this is the cause, Penny."

"Well, I need the information," she says, packing her things. "You're just going to have to get used to it. I'll just have to keep gathering data until I get enough normal readings, I guess."

Sheldon twitches.

"You intend to keep intruding?" He twists his fingers around the dry-erase marker he still has clutched in one hand. The cap squeaks as it rotates.

"It's for science, Sheldon."

In that instant, Sheldon can see the future. It is filled with endless interruptions by Penny attacking him with thermometers, sphygmomanometer, and any number of other instruments.

"I'll do it myself," he says, placing the marker in its rightful spot.

"Huh?"

"I'll take my temperature and blood pressure for you, Penny."

She shakes her head. "This is my experiment, Sheldon."

"You will never get a baseline if you keep interrupting my routine like this. More importantly, you will be disrupting my work and I cannot tolerate that. I assure you, whatever measurements I take will have much more fidelity than any you will take."

She's quiet for so long that Sheldon begins to worry. He has to consciously keep his hands where they are else they would likely stray to cover his throat and his midsection. He has known Penny long enough to realize his previous statement could possibly garner a highly negative and violent response.

"I'll think about it." And then she's gone.

In the CalTech cafeteria, there is heated discussion at the lunch table between Howard and Raj. Leonard, however, isn't listening. He's absorbed in his own thoughts.

Conversation ceases when Sheldon appears a few minutes later. The other scientist looks visibly disheveled.

"So…" Wolowitz drawls when Sheldon joins them. "Penny's running an experiment on you, eh?"

"More like ruining my life," Sheldon replies.

Leonard cocks his head to the side and contemplates. If it had been any other man, Leonard is sure he would be driven with a need to dig the spoon in his hand in the other's eye. But this is Sheldon and he is most definitely not enjoying the attention Penny is giving him.

Wolowitz scoffs. "Come on, Sheldon, this is an opportunity of a lifetime. If I had someone as hot as Penny experimenting on me…"

He doesn't finish the thought, but he doesn't need to. Everyone at the table is filling in the blanks with his own fantasy.

Except for Sheldon.

"I assure you whatever fantasies you may be harboring bear no resemblance to reality," Sheldon drones, digging into his lunch. "The constant interruptions are not only going to disrupt my work but likely my bowel movements as well."

Simultaneously, the fantasy bubbles all burst.

"Still," Howard continues, examining a piece of lettuce on his fork, "to be poked and prodded and examined…"

"Dude, you make that sound about as appealing as an alien abduction," Raj pipes in, looking sideways at his friend.

"And about as likely," Leonard finally chimes in.

Wolowitz makes a face and retorts, "Same to you, bro. I don't see Penny knocking on your door to perform whatever inappropriate and invasive experiments on you."

Leonard smirks. "No, but that's sort of the point of the experiment."

Sheldon visibly freezes. "You were informed of the nature of the wager between Penny and I?"

"As a matter of fact, I was," Leonard replies, leaning forward with a smile on his face.

"Do tell," Howard urges, also leaning forward.

"Penny asked me to help, actually," Leonard explains, taking a sip of his soda. "The experiment is to see if she can seduce Sheldon."

"Dude!"

"What?"

Leonard nods, unable to keep the grin off his face. "I know."

Sheldon clears his throat. "Actually, that isn't completely accurate. The experiment in question is to determine if homo novus can be seduced. I have informed Penny that such a claim is preposterous."

"Same thing," Leonard says, waving his hand dismissively. "As you've told us numerous times, you're pretty much the only specimen of homo novus."

"I suppose it is valid to draw transitive property parallels to this situation," Sheldon muses. "Still, I hardly think it's fair for Penny to ask for outside help. After all, it isn't as if she is conducting the experiment on more than one specimen."

Leonard thinks for a moment. He isn't sure why but he feels miffed on Penny's behalf. Sure, the experiment is a little strange and Sheldon is a lot annoying, but he can't help but be drawn into the whole silly idea.

Inklings of an argument form in his head and he realizes if he voices them, he's going to regret it. But it's for Penny and, if he's totally honest with himself, Leonard is curious, too.

"Well," Leonard draws out, "since there's only one homo novus, that we know of, and this is the first experiment of its kind, it seems reasonable to me that Penny should throw as many resources as she can at it. Besides, I'm the best reference she has outside of you, Sheldon, and you're certainly not going to give her ideas that might be in her best interests."

Sheldon pauses for a moment and Leonard waits for whatever response he may have.

"You have a valid point."

Leonard smiles, genuinely, and the lunch conversation turns to more mundane topics.

Penny breezes through her shift at The Cheesecake Factory that afternoon, barely registering that any time has passed. It turns out that when her mind is occupied, she operates on auto-pilot and that auto-pilot is really, really good. She tucks her tips, which are actually quite decent this night, into her purse and mentally sets it aside for any other materials she might need for her experiment. Or, maybe, she'll get those shoes she saw on the sale the other day instead. Either is equally important.

She reviews what happened earlier that day at CalTech on the drive home. Penny was both surprised, yet not, that Sheldon hadn't responded to her husky voice and close proximity tactic. That kind of thing always worked on other guys, but Sheldon wasn't just another guy. She would have to think of other ways to draw him out. Maybe he just needs more experiences like that.

When she reaches her apartment, Penny tosses all her stuff aside and reaches for the "Experiments" notebook. She writes a short list of situations to try with Sheldon and indicates those mini-experiments are an attempt to get Sheldon used to physical interactions.

Surely repeated exposure will eventually lead to acceptance, right?

Later that evening as Leonard and Sheldon are watching TV, Penny invites herself over. She takes up residence on the middle cushion of the couch and attempts to be absorbed in the program. It's a repeat of a Doctor Who episode she didn't really care for, so she instead turns her head to look at Sheldon.

He's doing a valiant job of ignoring her so she keeps staring at him.

A few minutes later, she gets up and gets a drink from the kitchen. When Penny returns to the couch, she deliberately sits a little closer to Sheldon. To his credit, he doesn't leap from his spot but he does squirm closer to the arm rest.

Out of the corner of her eye, she sees Leonard cover his mouth with his hand. Turning, she swears he's smiling and she raises an eyebrow in question. "What?"

He doesn't answer for a moment but finally replies with, "Oh, nothing." Penny's pretty sure his lips twitch again. Whatever.

Silence falls over the three of them again and, after a while, Penny stretches and leaves her left arm on the back of the couch. Sheldon slowly leans away and Penny can't help but smile. This is exactly what she'd wanted. Sheldon couldn't be paying more attention to her than he is right now, when he is explicitly trying to ignore her.

The episode comes to an end and Penny makes her move. She reaches over and touches the hair at the base of his neck.

Sheldon practically leaps off the couch.

"I'm going to bed!" he exclaims before running, literally running, to his room.

Penny's speechless. She'd expected a reaction but…not that.

Next to her, Leonard chuckles. She turns her gaze on him, raising her eyebrow again.

"Sorry," he says, coughing into his hand.

"Hmm," Penny muses.

Well, she did have other experiments in her book. She'd have to think up contingency plans for when Sheldon…escapes…like he just did. But, first, she has to record her findings.

Without another word, Penny gets up and walks quickly back to her apartment.

Leonard watches in silence as Penny walks out of their apartment. When the door closes he allows himself a moment to chuckle at what had just happened. Penny wasn't going to get very far if that was her approach. She's known Sheldon long enough to know that he doesn't respond to physical contact very well, especially when he isn't expecting it.

Leonard finds himself thinking about all the ways Penny could approach Sheldon to try to get a response. A part of him wonders if he should be worried that he's thinking about how to go about seducing Sheldon, but then he realizes that Sheldon really is a totally different kind of creature. Leonard can't deny that he's curious how Penny's experiment will go.

The door to the apartment suddenly opens and Penny strides in, Hello Kitty tote bag in hand.

"Forget something?"

"Yeah, sort of," she says and walks right past him, heading for Sheldon's door.

"I don't think you want to do that…"

But she's ignoring him and turning the doorknob. But Sheldon is prepared this time and it's locked.

"Sheldon, open the door," Penny says.

"I'm sleeping," comes a voice, muffled by the door.

"No you're not, your calendar says you're not going to bed for another hour."

"That's just a maximum cutoff time."

Leonard can practically feel Penny roll her eyes.

"I need your nightly temperature and blood pressure," she tries. "For science?"

There's no reply for a long moment and then Sheldon's door opens.

"Fine, but I'm doing it myself," he says.

"Okay, well, here," Penny concedes, handing Sheldon the supplies.

"Good night." And Sheldon's door shuts again.

"Wait!" Penny cries. "I need the results!"

"I'll e-mail them to you," he replies through the door.

"And tomorrow morning?"

"I've sent you a recurring meeting notice for temperature and blood pressure readings three times a day."

"Oh," Penny replies, deflating slightly. "Okay. Um, thanks."

She walks back out of the apartment, not even sparing a glance at Leonard who has been watching the whole exchange. He has never seen Penny this absorbed in something since her obsession with Age of Conan.

As Penny walks out of the apartment for the second time that night, Leonard gets it. He finally gets it.

Penny has always been curious about Sheldon. He saw it the day they met and the way she looked at Sheldon when he was explaining his whiteboard to her. And, miracle of miracles, Sheldon had responded to Penny's presence, something that shocked him then and still does when he sees his roommate react in ways he's never seen before. And these days that only happens when Penny does something that totally blindsides Sheldon's view of the world.

The revelation makes him sad and angry and jealous and irritated and all sorts of other feelings. But, really, he never made a move and what did he expect, that she'd suddenly wake up and figure out she was meant to be with him? Well, yes, but Leonard doesn't really want to admit that to himself so he just blows past that thought.

But...Sheldon? Really?

Leonard hauls himself off the couch and sighs, readjusting his glasses. He's not going to lie to himself (too much), he's curious what Penny will do and if he leaves things between them like they are, she'll shut him out. So he stuffs his pride into the far corner of his mind like he usually does and strolls out of his apartment and across the hall.

He knocks quietly on Penny's door and is half hoping she doesn't answer. Unfortunately things never really seem to go his way, and she does. She immediately has a defensive look on her face and she's leaning against the door frame with her arms crossed.

"What do you want, Leonard?"

He flinches at her flat tone but he plows on, not quite looking at her.

"About your request…"

"Yes?"

He starts to apologize but stops himself. He's decided to be the good guy in this, but that doesn't mean he has to be a doormat.

"Ok," he says. "I'll help."

The transformation of the look on Penny's face from ambivalence to sheer joy is almost...almost worth it. Well, just for the next 5 minutes or so.

She practically jumps on him, then, hugging him and Leonard doesn't feel an ounce of shame for enjoying it.

"But I'm not doing this all for you," he cautions. "This is still your experiment."

"Of course!" she exclaims, clapping her hands in glee. "You'll be a consultant or something. A reference."

"Great," he replies. "Just be sure to put me in your bibliography."

The next week goes something like this: Penny being tenacious, Sheldon feeling violated, and Leonard being amused.

Penny's never been this focused about anything, even in her aspirations to be an actress. She idly thinks she should throw herself at her career the same way she's throwing herself at Sheldon. She pauses at that thought and draws some parallels. The acting world is about as receptive to her attentions as Sheldon is. This gives her more resolve. After all, if she can seduce Sheldon, getting some acting gigs should be easy.

Right.

First she has to, you know, seduce Sheldon.

She's sprawled on her couch, running through the events of the week.

Penny has learned a lot of what Sheldon doesn't like, but that doesn't really help at the moment. He's forbidden (he actually said "forbidden") her from visiting him at work without his express and previously obtained permission.

When he effectively banned her from taking his temperature and blood pressure thrice daily, she thought he was overreacting. It's been a couple days since that incident, though, and Penny now realizes that maybe she was a little teeny, tiny bit forceful.

Penny sits up abruptly, realization dawning. She's never going to win this bet if she keeps getting cut off like she is.

"Ohhhhhh..." she groans, flopping back down as more insight comes to her.

She's been approaching this all wrong. Penny's almost always been the pursuer or aggressor in the relationship. Guys like it when a girl's in charge. At least, the guys she's normally into. She even went so far as to tell Sheldon she was a "big ole five" when it came to initiating sexual encounters.

But this is Sheldon. Sheldon. Penny thought it to herself before she started; it was an absurd idea because Sheldon was so different from any other man-no, person-she had ever met.

He's not going to react the same way most guys do. She knows he doesn't respond well to physical interaction, so flirty touches aren't going to work (which, of course, explains his bolting from the couch the other night when she touched his neck). He doesn't get any sort of conversation that isn't straight up and literal, so it's not like she can throw some innuendo his way and expect him to understand it. Penny's pretty sure Sheldon doesn't understand "coffee" so she's going to have to figure out new ways of flirting with him.

Time to change tactics.

Leonard's returning from work when he gets a text from Penny.

"Have time to be my reference?"

He frowns for a moment, then remembers.

"Sure. Just got home. Now?"

He diverts his path from his apartment to hers when he gets her reply. He stands just outside Penny's door, apprehensive. With a resigned sigh, he raises his hand and knocks on the door.

Penny greets him with a big smile and Leonard's spirits lift just a little. Sure, he's here to tell her everything she never wanted to know about Sheldon, but at least he gets to spend time with her.

"Hey, Leonard. Thanks for coming," she says, ushering him into her apartment.

"No problem," he replies, taking a seat on the couch. "So..."

Penny sits beside him and clasps her hands. "So," she replies.

"How do you want to do this?" he asks, pushing his glasses back up his nose. He idly thinks he really needs to get a better fitting pair.

"Well, I've been thinking," Penny starts. "I realized earlier today that my normal approach just isn't going to work. Sheldon reacts totally different from any other person on the planet when it comes to regular flirting and stuff."

Despite himself, Leonard grins.

"I was wondering when you'd figure that out," he says, giving her an appreciative glance.

"You knew what I was doing wrong and you didn't tell me?" she asks.

He puts his hands up, placating, "Hey, this is your experiment. I told you I'd be a reference, but like any reference book, you have to come to me."

"I guess you're right," she sighs, flopping back. "I'm just not really sure what to do now. This is unfamiliar territory."

She gives him a meaningful glance.

Leonard's hands move from placating to defense. "Don't look at me," he says. "I don't spend my days thinking of ways to seduce Sheldon."

She's giggling on the floor now and Leonard is chuckling with her. Maybe this won't be so bad after all.

"Okay, okay," she says, pulling herself back on the couch. "Well, what kinds of things does Sheldon like?"

Now it's Leonard's turn to level a look at Penny. "I think you know more than you think you do, Penny. You've been around us for a couple years now."

"I thought you were supposed to be my reference," she accuses.

"And I will be," he reassures. "But I think you have all the information you need, really. I'm just here to help you organize it in a way that makes more sense."

"Like how?"

Leonard shrugs. "Like maybe filling in some blanks. Let's start by what you do know. What kinds of things do you think Sheldon likes?"

"Well," she drawls sitting back in the corner of the couch. "There's the easy stuff: comic books, video games, and things to be in perfect order all the time."

Leonard nods. "Okay, we'll talk about those, but what does Sheldon like...well, actually, love the most?"

She arches an eyebrow at him in question.

"Do you remember the first day we met?" he asks, trying another way.

"Yeah, the day you guys tried to go to the sperm bank?"

Of course, she would remember that one mortifying tidbit of an otherwise pretty good day in their lives.

"What had Sheldon said? Something about mastur-"

"Um, yeah," he interrupts. "Let's not talk about that part. I was talking about when you came over."

"Oh, sure," she says. "Um, I asked about the whiteboards. You know, he did seem pretty excited about that."

"Bingo," Leonard said, smiling.

"Oh! Sheldon loves his work."

Leonard nods. "I really think there hasn't been a word or words invented in the English language that could adequately describe what Sheldon feels for his work. It's his life. I'm convinced the fact that he has hobbies is just a fluke or self-preservation by the subconscious of his mind so he doesn't go completely crazy."

Penny grins at him. "Oh, but he's not crazy, his mother had him tested."

"That was years ago," he grins back. "He's never been retested."

Penny giggles for a moment and then she pauses. Leonard can practically see her thinking.

"That explains...a lot, actually," Penny muses.

"Like?" Leonard asks, curious where her mind is going.

"Well, like why he's so strict about schedule and routine and stuff. And, you know, why he didn't want me interrupting him at work. I guess that was kind of selfish of me," she reasons. "I'm just doing this for myself, but that's his work, his life."

"Yeah, he takes it pretty seriously," Leonard says. "He's kind of insufferable and impossible about it, but he's the most capable of any of us, or several of us combined."

"So, everyone else is just jealous."

It wasn't a question and it makes Leonard squirm.

"Let's just say we know he's incredibly smart and he does, too, and he makes sure everyone else knows. That doesn't always make people happy."

"Right," Penny says, flatly, but she lets it drop.

"Well, crap," she says after a moment. "How am I supposed to work with that? I don't know anything about physics and the last time he tried to teach it to me it was a disaster."

"But he did try," Leonard points out.

"Well, yeah, but so what?"

"Penny, probably the next best thing for Sheldon other than doing his work is sharing his work. He would like nothing more than for everyone else to love physics the way he does. It's like...it's like your favorite song. You want everyone to know about it and to love it, too."

"But, Leonard, I don't think I could pretend to be interested in physics," Penny says. "I'm sorry, but I just don't find it all that exciting."

"You don't really have to."

"Huh?"

"Look, Penny, Sheldon can be pretty complicated, but for the most part he's very straightforward. He'd be happy talking physics to an empty room if he had to. Sure, he likes it even more when you interact, but there are probably only a half dozen people on the entire planet that could talk string theory with Sheldon."

"So, what am I supposed to do?" Penny asks, a defeated look on her face.

"I think," Leonard starts, "it's just as simple as respecting Sheldon and what he does."

"But you guys make fun of him all the time."

"We're not trying to flirt with him."

"Oh, true," Penny muses. "I guess it's like me and my acting. I get a lot of flack for it."

"Or the whole deal with the psychic," Leonard adds.

"What's wrong with my psychic?"

"Well, you can't really be serious about..." he trails off when he notices her eyes narrowing. Leonard quickly realizes he's about to step in it right after he'd told her not to do that to Sheldon and thinks that maybe he should take his own advice.

"...the price you have to pay to see her," he recovers. "Surely that adds up?"

"Ugh, tell me about it," she says as she flops backwards again.

She misses the look of relief that crosses Leonard's features.

"Oh, crap!" Penny exclaims, standing quickly. "I'm gonna be late for work! Thanks for the info, Leonard."

"Anytime," he says. "I'll just let myself out."

"Thanks!" she calls over her shoulder as she heads to her bedroom.

Leonard shakes his head as he closes Penny's apartment door. He reflects on the things he said and wonders if maybe he should be a little more respectful of Sheldon himself.

He finds the other man holding a blank whiteboard in the middle of the room when he enters their apartment.

"Hey, Sheldon," he greets, dropping his keys in the bowl.

"Oh, good, Leonard, you're home. Would you take these whiteboards and throw them out?" Sheldon asks, nodding at a stack of 3 whiteboards by the couch.

Leonard glances at them quickly and then pauses. "Sheldon, these are mine."

"Very well, you can at least take them into your room. I need space to continue my equations and your derivative scribblings are taking up a significant amount of real estate."

Leonard gapes, all thoughts of being civilized and respectful flying out of his mind.

"Well?" Sheldon's look is decidedly impatient.

Wordlessly, Leonard grabs his whiteboards and takes them to his room. He's pretty sure if he'd refused, Sheldon would have just thrown them out the window.

At work that night, Penny's a little more distracted than usual. She doesn't mess up any of her orders, though, which is good. She can't really afford to lose her job or be given less shifts at this point. But she's thinking a lot about what Leonard said and what she's realized and she knows she has to change tactics if she wants to seduce Sheldon.

Oh, and win the bet, of course. That comes first. Right.

The sudden shift in her thoughts makes Penny pause and Bernadette nearly runs into her.

"Sorry, sorry, Bernadette, I just...got distracted."

The other woman grumbles a little and then moves past. Penny's pretty sure she heard the words, "not the first time these days" come out of her mouth and she wonders if she's letting this experiment negatively affect her performance.

And where the hell did that wording come from?

Penny's eyes widen in shock and she's pretty sure she's figured out that science changes one's speech patterns, but that's a topic for another time.

She turns her thoughts back to the revelations of the day and Penny decides she's going to take a more passive role, when it comes to Sheldon. She has to draw him to her, she can't go to him because he'll just run and shut her out even more and then she really will lose.

It's the first time she realizes this experiment could change the characteristics of their friendship in a negative way if she doesn't do it right.

And what if she succeeds?

The consequences and possibilities start pouring in and Penny has to sit down.

Is she prepared to deal with the consequences if she does manage to seduce Sheldon?

The thought is mind boggling, but the corollary follows. Is she prepared to deal with the consequences if she doesn't seduce Sheldon or, worse, alienates him in the process?

Penny suddenly realizes she and Sheldon have become integral parts of each other's lives. She's not sure she could easily cut him out of her life, but she's also not sure she's ready to, well, date him.

"Crap," she whispers. "What have I gotten into?"

Throughout the rest of her shift, Penny waffles back and forth between moving forward and conceding defeat. Just when she thinks she's decided to quit, her pride rears up and she decide she can do anything but quit.

Sheldon would be insufferable, for one, but she can't even really make her mind believe that's the reason she doesn't want to give up.

The drive home is slower than normal and her thoughts race as she crawls through the traffic made worse by construction.

On some level, Penny realizes she's always gravitated towards Sheldon. Neither Sheldon nor Leonard are the types of guys she normally goes for but Sheldon is, at least, taller than her. And, if she's completely honest with herself, she did feel an attraction to him that first day. He really does have amazing eyes and arms, though the rest of him may be skinnier than she prefers.

By the time she finally drags herself up to her apartment, Penny has decided. She's going to keep going with the experiment and deal with the consequences when they happen. But, she's determined not to lose and, when she wins, she's determined not to hurt Sheldon. Penny's almost certain the man has never had a significant relationship in his life. She's had more than she'd like to count, always being the one to fall in love quickly, but they've never turned out well. It'd be downright cruel if-when-she manages to seduce Sheldon to just drop him.

No, she'll handle that right. Maybe it'll work. Maybe it won't.

But she's not going to hurt him. At least, not on purpose.

Crap.

The next day is very...strange...for Sheldon. He's noticed he's almost always on edge, waiting for Penny to burst in on him at every inopportune moment. Sometimes, he catches himself relaxing, but he knows that isn't a good idea because she can strike at any moment.

He spends most of the early evening in anticipation and it's becoming quite a distraction that Penny hasn't done anything, yet. Sheldon is almost tempted to look in on her.

Almost.

Doing so would, of course, make her think she's having some sort of effect on him and he can't have that.

"Hey, Sheldon. You coming to dinner?" Leonard asks as he pulls on his jacket.

"Although it is Anything-Can-Happen Thursday, I'm going to opt to stay in tonight, Leonard."

Leonard shrugs and opens the front door. "Ok. See you."

Again, the feeling of relaxation begins to settle over Sheldon, but he forces his senses to be alert. Penny could come in at any moment, after all.

Instead, his phone pings, and it's a testament to how anxious he is that Sheldon actually jumps off the couch.

It's a text from Penny and, while that isn't necessarily unusual, the composition of it is.

"Hope I'm not bothering you. Want me to bring home dinner? And, if so, what and for how many?"

Sheldon blinks.

Penny never offers to get dinner on a non-routine night.

It is Anything-Can-Happen Thursday, though...

"I'm not feeling particularly spontaneous tonight. Pizza will suffice. It will just be the two of us."

He ponders for a moment, then sends a follow-up.

"If that's okay with you."

Ordinarily, Sheldon wouldn't have cared either way what Penny's response was. But tonight, he finds himself staring at the phone in anticipation. It pings.

"Pizza it is. See you soon!"

The next several minutes are still filled with anxiety, though. Sheldon knows Penny is coming over, he just doesn't know when. Every set of footsteps he hears-or doesn't hear-makes him jittery.

He is expecting her to burst through their front door at any moment, when he least expects it. He is expecting her to just appropriate any spot available, even if it isn't the correct one, for the food.

He is expecting everything except for what actually happens.

Three knocks sound on the front door.

Who could be coming over?

The knocks come again and how Sheldon's really alarmed.

The third time they come, a voice accompanies: "Sheldon?"

Sheldon's eyes nearly bulge out of his head. It's Penny. And she's knocked.

She knocked. Penny doesn't knock.

"C-coming," he stutters out as he finally makes his feet move.

"Hi, Sheldon," she greets with a smile.

"Hello," he says, slowly, suspicion flitting through his mind.

"I hope it's not too late. Traffic was a bear," Penny explains. "May I come in?"

Sheldon pauses. Did she just-?

"Sheldon?"

"Of course," he says, confusion replacing suspicion as he steps aside to let her in.

"Where would you like me to put the pizza?"

This time, Sheldon is full out gaping.

"Are you unwell?" he blurts out.

It's Penny's turn to look confused and she tilts her head to the side as she looks at him. "What?"

"You don't appear to be...functioning normally."

"Uh, well, I can assure you I'm 'functioning' just fine. I'm just hungry."

He should be happy with that answer. He should just move on. But the fact that there was no strange-possibly sarcastic, he's never quite sure-remark about his words is also another clue that something is different.

"On the kitchen island is fine," he says, finally.

While they're eating, Sheldon's thoughts race between two schools of thought.

1) He should observe Penny and determine if she is or is not suffering some sort of ailment.

2) He should stop caring because clearly this is all part of Penny's nefarious plan to try to make him expend effort and energy paying attention to her.

He doesn't know how he should feel about either option. The fact that options exist indicate he's invested more than he ever meant to in this experiment of hers.

And then there's the fact that she's not trying to poke and prod him with substandard medical equipment or pester him with inane questions or, god forbid, trying to touch him.

In fact, if Sheldon didn't know any better, he would think Penny is deliberately trying to not do any of the things that upset him. The lack of those actions he was sure she would do is, oddly enough, upsetting him.

After dinner, they're watching reruns on BBC America. She's sitting beside him, laptop open. Sheldon is very much aware that Penny is not paying attention to the Doctor Who episode they're supposed to be watching. She's been typing fairly consistently for the past 13 minutes.

"If you're not going to watch, perhaps you'd be more comfortable in your own apartment?" he suggests.

"No, it's okay," she says, not looking at him. "It's good background noise. Besides, I like Amy in this episode."

"Background noise for what?" he asks despite himself.

"The findings for my experiment."

"You're done?" Sheldon is unsurprised to feel hope swell but mystified as to why he feels a pang of regret. He files that piece of information away for later musings.

"No, I'm just writing down the findings to date."

He can't help himself; he leans over to look.

"Hey, no peeking!" Penny exclaims when she notices what he's doing. She clutches the laptop to her chest and leans away.

"Surely your findings cannot hold anything I don't already know. After all, I am the subject."

"Maybe. But you're just going to have to wait until I publish the results."

She's still leaning away from him, but she loosens her grip on the laptop and he can almost make out some of the words. Against his better judgment, Sheldon leans closer. She keeps moving further away from him.

"Sheldon, if you keep pushing like this I'm going to fall over," Penny says.

Her words make him realize just what he's doing. He's leaned over her, nearly on top of her, and very close. Penny's smiling softly up at him and he blinks, unmoving. He frowns slightly, unsure of what to do next.

"Sheldon? Can I get up?"

But he just continues to stare at her, perplexed, more so when she very gently, but firmly, pushes him upright with a single finger on his shoulder.

"Thanks, sweetie," she says, still smiling. And then she goes back to her report.

Sheldon automatically turns to face the TV but he's not watching what's on it. Penny's behavior has been completely foreign to what he expects from her and he doesn't know what to make of it. He's certain, if she had been following her previous behavior patterns, she would have attempted to initiate some sort of physical contact more intimate than the push she just gave him.

He chastises himself for worrying about something so trivial and attempts to go back to the TV show.

But, every once in a while, the apartment's faint draft wafts the smell of Penny's shampoo under his nose and disrupts his attention. The scent is lavender and Sheldon realizes she's using the contents of the second smallest gift basket he'd given her for Christmas.

End Part 1