Sheldon is doing his best to care about Koothrappali's situation when Penny arrives on the scene. "Guys!" she practically screeches, before regaining her composure and hardening her countenance into what he can only assume is an impression of him. "I have found myself requiring willing test subjects for an experiment I will be conducting."

"No," Sheldon, Leonard, and Howard reply simultaneously. Raj shakes his head fervently. They know her all too well.

Penny pouts. "Please," she whines, drawing out the single syllable. "I finally got a bartending shift, and if I can pull this off it means a pay raise, but I've gotta get some practice in."

They exchange looks. Sheldon is the first to speak.

"Penny, I applaud you for your attempt at upward mobility, but perhaps we are not the best subjects for this experiment. After all, only Leonard and Howard regularly consume alcohol." His tone is somewhat soothing, but she can tell that he's just trying to save his own butt.

Raj holds up a hand and gives her a significant look. She raises her eyebrows. He nods.

"Well, it looks like Raj is up to it," she says pointedly.

Sheldon avoids her eyes, but he still feels a shock of disappointment when she sighs and concedes. He spends the next half hour watching her mix drinks and socialize with the others, and he realizes that he might need to revise his work thus far.

Instead of accompanying the others on their Cheesecake Factory expedition, he stays behind and struggles through the possible solutions. By the time that Leonard returns to regale him with boring tales of Raj's failure, he is, to put it simply, "fed up".

Sheldon has never enjoyed consulting others; he considers it generally beneath him. However, this subject is so far outside his areas of expertise that he finds himself driven to it.

"Leonard?" he asks hesitantly.

His roommate pauses whatever insignificant activity he was performing and turns around. "Yeah?"

"I want to ask you something."

Leonard looks at his roommate, who is bouncing slightly on the balls of his feet. The shorter man smiles slightly. "What is it, Sheldon?"

He opens his mouth. Closes it. Opens again. "What am I doing wrong?" he asks plaintively.

Leonard smirks. "I think you'll have to be a little more specific than that."

Sheldon sighs, relaxing his shoulders. He looks at the ground. "Penny does not seem to comprehend my expressions of interest. Additionally, she seemed displeased with me earlier when I refused to allow her to mix an alcoholic drink for me. I do not understand. Popular media is obviously deceitful: this process of wooing was never shown to be this darn hard." His Texas accent comes out on the last few words. Leonard smiles, feeling a sudden rush of empathy. It was always nice to be reminded that his roommate was human, after all. No matter what he pretended.

"Sheldon," Leonard said, as gently as he could, "I think you might need to be less...well, a bit need to change. Somewhat. I mean, you're really uptight and closed up about what you like. Penny...she's a really social person, and she probably isn't sure how it would work between the two of you when you're so critical and antisocial."

Sheldon blinks, taking in the words. "Let me confirm this. You're suggesting that my behavior is putting my viability as a mate into question?"

He scrunches up his face. "I...guess? I mean," he adds, translating to Sheldonese, "a reasonable amount of sociability is a desirable trait for the male of most species."

"Fascinating," Sheldon breathes. "I think you may be onto something, Leonard. Yes. That does fit the existing data. Well done."

Leonard feels a puff of pride. It was always nice to be able to do something that Sheldon couldn't, and if he actually acknowledged it...the high was practically incomparable. Hey, maybe it hadn't skipped a generation after all. He'd never really wanted to follow in his mother's footsteps, but if his analyses were always that spot-on...

"Don't get any ideas," his roommate says suddenly, as if he had been reading Leonard's mind. "It wasn't that well done."

Sheldon inhales deeply. He couldn't believe that he was going to do this. His mother would definitely have his hide for it. Still, he thinks back to the beautiful equations and nods, feeling his heart swell with determination.

He strides into the bar area, takes a stool, and says with confidence. "I'd like a Cuba Libre, please."

Bravely, he adds, "And make it promiscuous."

Penny spins around, eyes wide. "Sheldon," she greets him. He does not quite recognize her tone—all light and airy, like she's giggling the word—but he finds that he rather likes it. "What are you doing here on a Friday night?"

Sheldon shrugs, and she almost laughs at his attempt to be casual. "I felt like being social. Also, I believe that I ordered a drink?"

"You don't drink," she says dryly.

He raises a finger. "I didn't drink. Please, fetch me my beverage before I change my mind."

"Ooh-kay," Penny mumbles, turning around to mix the drinks. While she's at it, she refills her own glass, hidden under the bar. If Sheldon's drinking, there's no way she's staying this sober.

About an hour later, and he's consumed more than one promiscuous Cuba Libre. Sheldon is starting to feel quite libre himself, pounding away at the keys like he only dares to do on his wildest days. He plays love songs, mostly, and the crowd seems to eat it up, but his eyes are on Penny.

She can't shake his intense stare, and it does something funny to her heart. So when he asks her to come over and do a duet with him, her heart practically stops.

"Sweetie, you hate my singing," she says, slowly.

Sheldon bobs his head. "Yes, but that does not matter. I am feeling so liberated, Penny! Sing with me."

His blue eyes are so wide and innocent...she can't resist. She whispers to one of her nice coworkers, and the girl just nods and takes her place. Penny slips out and over to the piano.

"I'll start," he says, in what would have been a soft voice had he not been riproaringly intoxicated. There is no introduction, but from the first few notes, she recognizes the song.

Penny realizes she's probably the only reason Sheldon even knows this one. It's a popular song, and she likes to turn the radio up all the way and sing along, pretending that she has somebody to sing it with.

Hey. Now she does.

Dutifully, she chimes in at her part. They are both slurring their words a little bit, and he slows the tempo as she trips over the words. Still, when they reach the chorus together, it is beautiful. They might both be going flat, but they're going flat together.

Their voices drift down, eyes still locked. Their harmony shifts to a perfect unison.

Suddenly, she feels very transparent and vulnerable, like her skin is just plastic wrap over all of the feelings she's been dying to keep inside. It doesn't seem so bad, though. Penny smiles. Maybe it's because he's kind of on display, too.

He grins at her and almost topples over. Yeah, she'll definitely need to help him home tonight.

"Lucky I'm in love with my best friend," a phantom croons in his ear. Sheldon squints his closed eyes and tries to speak, but his lips have been glued shut.

"P-penny?" he manages finally.

A giggle. "Yeah, it's me. You fell asleep in the car on the way home." Something warm nudges him.

Sheldon sits up, and slowly registers his surroundings. "Oh," he says shortly. She laughs again, gently.

Somehow, he finds his way up the stairs, through the door, and into his bed. He doesn't even brush his teeth before he collapses.

Penny doesn't have it so easy. She could hold her drink a lot better than he could, whether from years of practice or just natural ability, and so she was forced to lay awake. The song kept running through her head, and eventually she just got up, jammed headphones over her ears, and listened to it online. She hummed along, but her heart was going much faster than the beat.

She has it bad, and she doesn't know what to do.

The look in his eyes is plastered to her eyelids. Penny knows that she can't take this any longer, and she wants to jump for joy at the thought that those same feelings had shown on his face. Still, her heart lurches. What if it doesn't work out? Is she crazy for thinking that this could ever work?

"Penny, stop psyching yourself out," she says aloud. She likes to give herself pep talks sometimes. "You can talk to him in the morning."

Her eyes drift to the clock. 2:13. A sigh escapes her lips. It's gonna be a long night.

From the instant Sheldon's eyes blink back open, he recalls the events of the previous night. He feels somewhat embarrassed that he allowed himself to become so intoxicated, but he also remembers the way that she smiled and sang with him. It was worth it, he judges, and performed its function.

Something seems to be pressing against his head. He realizes that he must be experiencing veisalgia. He feels...well, as Penny would say, he feels like utter crap.

He stumbles out of bed and commences his morning ritual. A note on the mirror informs him that Leonard is out for the day with Elaine. Well enough, he would only have mocking words for Sheldon, anyway. The shower makes him feel marginally better, but he is still slightly nauseated and his head aches dully.

Despite all this, he feels an impetus to see her, to find out if his actions really yielded a result of consequence. Sheldon approaches his front door and pulls it open.

Penny tumbles in.

At first they're a mishmash of misplaced limbs, but when she rights herself, he is still regarding her with the same intense expression. "Penny," he says absentmindedly. She notices that his hair is sticking up messily, and fights the urge to comb through it with her fingers.

"Sheldon, hey, I was just coming to check on you. You feeling okay?" Penny presses a hand to his forehead, although why she does this she isn't quite sure. He does not brush away her touch.

He clears his throat. "I do seem to have vei—a hangover," he adds hastily. "My head is clearing, however."

"Good," she says, in a tone more breathy than her usual. His stomach responds oddly to this. "I'm sorry, babe, I should have cut you off."

"It is not your responsibility," Sheldon responds, shaking his head slightly. Her touch has moved from his forehead to his arm, but there it only rests on his shirt. He finds himself wishing for skin-against-skin contact again.

Good Lord, this business of romance really is horrifying. A few months ago, he would have never imagined a desire within him to touch anybody's bare flesh, but one brush from Penny and he can't stop swallowing and nearly hyperventilating.

Penny pulls back slightly. Sheldon seems to be getting uncomfortable, and her heart sinks a little. "Well, I'm glad you're okay," she says awkwardly.

He nods, and she turns to make an exit, but his long fingers catch her arm at the crook of her elbow. "Wait."

She looks back at him. His lips are slightly parted, but no words come out.

"Last night..." she says softly. "Do you remember trying to kiss me?"

"I have an eidetic memory," Sheldon reminds her stuffily. "I remember—"

"Everything, yeah, I know." How did he still manage to be so condescending when he was hung over? "Why did you...?"

He avoids her eyes. "I was led to believe that it was the next step after a mutual interest had been established, and it seemed that our duet performed that function. Why did you stop me?"

"Sweetie, you were drunk. I didn't know if you, you know...meant it." Feeling bold, Penny traces his jawline with her hand. He closes his eyes for a second.

When his eyelids flutter back open, his gaze is astoundingly strong. She's never been the swooning type, but that look could definitely make a weaker woman's knees buckle. "Can we attempt that again?" he asks quietly.

Instead of replying, she leans forward and kisses him.

Sheldon tastes like peppermint and innocence, with the slightest hint of rum still coloring his breath. She smiles into the kiss. He is holding her very gently and carefully, as if she might break. She hasn't had that kind of consideration from a man since...

Well, never, actually.

"I'm sorry," Leonard says helplessly, for about the fifth time. Elaine rolls her eyes at him.

"For the last damn time, Leonard, it's not your fault that your car battery went dead." She grins and snatches at his hand. "Besides, we can have a stay-in movie date at your place."

They reach the door. The handle proves unlocked, so Leonard pushes it open. After a second, he pulls it closed again, smiling slightly.

"What?" Elaine asks, raising a single eyebrow. "Sheldon in there?"

He responds by opening the door again, ever so quietly. She peeps in, laughs deeply, and closes the door again. "Never thought I'd see the day."

"I'm impressed," Leonard admits. "Lip-to-lip contact?"

She laughs again. "Whenever he caught us making out, it was always, 'Leonard, are you unaware of the hordes of bacteria that can be transferred through this sort of behavior?'." Elaine's impression of the physicist is positively uncanny.

He stops laughing and holds up one hand. "Wait, I think they're talking now," he whispers. They crowd around the door.

"Sheldon Cooper, you're out of your friggin' mind if you think I'm signing a relationship contract," Penny says hotly.

Sheldon sighs heavily. "Penny, Penny, Penny, why are you being so unreasonable about this? It's a perfectly rational—"

"Rational my ass! I am not gonna sign some piece of paper that says we're dating! We're going to go about this like normal human beings, Sheldon."

Leonard and Elaine exchange a look.

"My place?" she asks in a dramatic whisper.

He nods fervently. "Definitely your place."

Before they leave, he sneaks one final glance at the arguing pair. Their eyes are fierce, but still surprisingly gentle, and he wouldn't be at all surprised if they started kissing again at any moment. Leonard shakes his head. "Those crazy kids," he murmurs, smiling. He slings an arm over Elaine's shoulder and they walk off.

He even dares to whistle.

End Notes: The interval—a perfect unison. Say it with me: awww.

The soundtrack to this is now available on my tumblr, and the link is posted on my profile on here, so if you enjoyed the story, check it out. Thank you to all of my faithful readers, especially those of you who take the time to review!

If you liked this story, please read my other Shenny works! Also, I am currently working on two oneshots to be a companion to this story: Consonant and Dissonant. Keep a look out for those!