A/N - This has been in my head for weeks. I feel better now.

There was a moment of hesitation before Sheldon allowed himself to knock on Penny's door. He was used to asking Penny for favors and most of the time, she was always willing to help him out. But this one was going to be a little unconventional, and he wondered if he was crossing a line. Maybe he was asking too much of his baffling friend Penny. But he figured she was used to his unusual requests, so he went for it.

Knock knock knock. "Penny." Knock knock knock. "Penny." Knock knock knock. "Penny." Sheldon would never admit it, but most of the time, he did this just to annoy her. It worked for a while but now she was accustomed to his quirky entrances. In fact, she'd probably be more annoyed if he stopped doing it.

Penny opened the door on the last knock with her customary smile that always made Sheldon feel just a little bit better about himself. There were few people in his life who smiled at him like that. He seemed to elicit the opposite reaction most of the time, actually. So it was always nice to see a friendly face.

"Hey, sweetie. Come on in." Sheldon liked that she didn't ask what he wanted and instead invited him in.

"Can I offer you anything to drink? I have...vodka and chocolate milk. I wouldn't suggest drinking them both at the same time, though. Unless you're really drunk."

"I'll have some chocolate milk, thank you."

Penny made her way to the small kitchen and got to work. "So, Sheldon, what can I do for you today? You look deep in thought."

"Well, I am, actually. I was wondering if you could do me a favor."

"Are you sure about that? Look how the last favor worked out for you."

Sheldon cringed and felt the back of his neck. "Yes, well, my hair has grown back, and I have decided to forgive you for that." He was just starting to get over the failed haircutting experience of 2012. "I suppose that was just as much my fault as it was yours."

"Wow, the great Dr. Sheldon Cooper actually taking blame for something. I'm shocked."

Yes, well, he didn't really think it was his fault at all but if it made her feel better, he'd go with it. For now.

"Anyway, tell me what's on your mind, sweetie."

Even though Penny said she called everyone sweetie, Sheldon did not have any evidence of this. To his knowledge, she didn't even call Leonard sweetie, and he was her boyfriend. Sheldon was pretty sure this endearment belonged to him, and he liked it. He'd never been anyone's sweetie. Just a moonpie.

"Okay, well, I'm finding myself on the horns of a dilemma, and I came-"

"You're on the what of a dilemma?" Penny already looked confused. This was not a good sign.

"The horns, Penny. Pay attention. Amy Farrah Fowler has expressed her displeasure with my desire to keep any kind of digital stimulation to a minimum in our, ahem, relationship. Since we've been seeing each other for nearly two years now, I thought that I might rethink my position on the subject and take this thing to the next level. I owe her that much; she is a very loyal companion, after all."

Penny looked less confused now. He figured once she knew it was a matter of the heart, she'd understand.

"Okay, yeah, that's not exactly a secret. She texted me about it almost the second you left her place. And, Sheldon? She's so excited. Like, you made her year when you agreed to think about getting more physical. And I am proud of you for making that decision, too. Amy really does deserve it."

"I agree, although I am still a bit hesitant. I want to give Amy what she wants, but I'm still not comfortable with the amount of germs I'll be exposing myself to.

It wasn't just the germs. He'd spent a lot of time over the years thinking about what giving himself physically to a woman would emotionally entail, and for someone who was in his thirties and not used to such closeness, it was still fairly terrifying. But he figured it was time to move out of his comfort zone and see what it's like on the other side. If nothing else, Sheldon Cooper did not want to die a virgin.

"Well, I think you'll find it's not that bad once you do start doing it with more frequency."

"Yes, well, we'll see about that. So that brings me to why I'm here this evening. Penny, I'd like for you to teach me how to kiss."

She just stared at him and he started to get uncomfortable with how her eyes were searching him. Penny sometimes had this uncanny ability to see right through him. Like she knew him. And he never could figure out how or why or what he was supposed to do with that feeling.

"Sheldon...first of all, how on earth am I supposed to even do that? And second, why do you need me to do that? You've seen thousands of movies and TV shows where people kiss. Surely you can figure it out on your own."

"I know the visual, yes. While I'm positive I could figure it out on my own, I wanted to get your guidance. Because out of everyone I know, you're the most experienced in this field."

Penny looked a little hurt by this, but he didn't know why. She was an expert and that wasn't a negative trait, at least not in his eyes.

"Gee, Sheldon...thanks." She looks deep in thought as to how to proceed with his request. "Well, I guess I can help a little. Here, come sit next to me, I'll see how I can explain this without us actually having to cheat on our significant others."

Sheldon sat next to her on the small sofa and couldn't help but notice how fragrant she smelled on that particular evening. But this wasn't a new thought, really. Penny always smelled good. It was something Sheldon had come to appreciate about her.

"Now, Moonpie, you know you're kind of going to have to touch her and let her touch you? I know how you feel about stuff like that. Are you ready for that kind of closeness?"

"Well, to be quite honest, no. But I want to be. I have come to the realization that this is the right time for such things to happen. And I'm sure that someday I'll actually come to like it."

"Okay. Okay, well, let me think about this."

Penny unconsciously licked her lips and Sheldon watched with rapt attention. He told himself it's because he's trying to learn from her. Yes, this is why he's so interested in her lips.

"Okay, kissing. How to kiss. I've never really given it much though, I've just kind of...done it. Hmm. When you're at a point where she is expecting you to kiss her, you kind of lean in towards her face, and she'll kind of aim her lips at you. I mean, I'm pretty sure that's what Amy is going to do. She's had about as much experience with kissing as you, so you guys at least have that advantage. Anyway, you'll want to lean in and, you know, just press your lips to hers. Softly. Don't make it too intense the first time or you'll have nowhere to go from there. And then see how she reacts. If her eyes are closed and her lips are puckered, she'll want more. If her eyes are open and she looks unhappy, she will definitely not want more and you will probably have to rethink this whole kissing thing."

She stops again to think about the next step. Sheldon is completely wrapped up in it. "It" being her voice, her eyes, her delivery.

"Interesting. I think I follow so far. Please go on."

"Okay, so once you gauge her tempterature and you know she wants more, give her more. Make the kiss a little longer. Now, Sheldon, are you familiar with French kissing?"

He sighed and said, "Yes, I am aware of the mechanics. It sounds utterly disgusting to me, but I am sure that's what Amy is expecting."

"I think you're right about that. So what you do is, you stick your tongue in her mouth, basically. Lick her lips a little. Lick her tongue. Just kind of...explore her mouth with your tongue. And she'll do the same. I know it sounds like torture to you, and Sheldon? Really, if it's too gross, just don't do it. She'll know you hate it and this will end the kissing altogether."

Sheldon certainly did not like the sound of French kissing, but he'd give it a shot. He didn't want to lose Amy, and who knows, maybe he would like it. Recently he had an epiphany-ever since meeting and bonding with Penny, he'd become more open to participating in new experiences, and sometimes he even enjoyed it. She was so adventurous; so outgoing, it was almost infectious. Sheldon had never known anyone like her. And just knowing her made him feel like he could do anything, and he planned on using that mentality with Amy and her wishes for a more physical relationship.

"Okay, so we've got basic kissing and French kissing down. So after that, if you want to take it further, maybe bite her lip just a little. Like, don't make it bleed or anything, but give her something to think about. You may want to prepare yourself for second base after that, though, 'cause by then Amy's motor will definitely be humming."

Now it was Sheldon's turn to look confused. "Bite her lip? People really do that to each other?"

"Yes. It's nice sometimes," she said, blushing just a bit. "It's kind of like...you're claiming ownership. Caveman-style. Just trust me on that, okay?"

Sheldon let all of this sink in. He was not only supposed to stick his tongue in her mouth, but he had to bite her lip, too? What had he gotten himself into?

"Oh, and while this is happening, you'll want your hands participating, too. Put them in her hair, cup her face, grab her hands...just touch the girl. I promise you, sweetie, she's going to be putty in your hands."

"Well, that may be. She does have an intense craving for physical stimulation. But Penny, I must admit I'm a bit baffled about the French kissing and the biting. What do these things accomplish? And you think Amy is going to want that?"

"Amy is probably not very sure of what she wants, but I have a feeling she'll be keeping an open mind about anything you try. I mean, there are some exceptions, obviously, but not many. Trust me, Sheldon. Kissing isn't hard."

"I just want this to be satisfactory to her. I wouldn't want to disappoint her on the first try."

Penny sighed. "Oh, honey, I'm sure you're not going to disappoint her. She cares about you and knows that this isn't exactly your thing. You know what? I wish I could just...show you. It would be so much easier. But I have a pretty good feeling Leonard wouldn't be too happy about that."

"That is understandable." Sheldon kind of hated Leonard at that moment and he didn't understand why.

Penny looked deep in thought. "Oh, wait! I'm an actress, right? If I were an actual, functioning actress, I'd be kissing guys all the time. And it's not like we're kissing because of any real emotions or anything, right? And I'm sure Amy won't mind you kissing me if it's for your education. She'd probably even thank me. So we'll just think of this as an acting...workshop. Yeah, that makes it sound a lot better."

"I have no idea what you're talking about, Penny, but I'll just go ahead and agree with you." Well, he had some idea of what she was saying. It all sounded rather morally ambiguous, but he wasn't going to argue. Penny was in charge here.

"Do you mind if I show you? Would it totally gross you out to practice with me?"

"I think empirical data could only help my situation at this point."

"Sheldon. English."

"No, I don't mind. It will be easier to apply if I learn it the hands-on way. So to speak."

Penny looked at him with a mixture of fondness and frustration. He was used to it.

"Okay, good. Scoot closer. Now, show me how you would kiss Amy for the first time."

Sheldon hesitated. He wasn't sure if this was a good idea or a very, very bad one. While he was thinking about it, Penny said softly, "It's cool if you don't want to practice. I'm sorry I even brought it up. I don't-I don't know what I was thinking."

Instead of answering, in one quick motion, he put his lips on hers. Her lips were soft and slightly wet and he liked it just fine. He looked at her to gauge the reaction, just as she'd instructed. Her eyes were still closed, so he took that as a sign to keep going. He kissed Penny again, and she kissed him back, and he finally understood everything anyone had ever said about kissing.

She was the first to pull back. Penny cleared her throat and said, "Well. That was nice. Of course you'd be good at it, you're good at everything. Amy will like that just fine. Whew. So...any more questions?" Her face was pink and her eyes were sparkling and things that never made sense to Sheldon were now perfectly clear.

He fidgeted a bit, picking at a stray strand of fabric from his black undershirt. "Actually, I was wondering if we could try...the French kissing. Just to make sure I know what I'm doing."

"Oh, um, well, yeah. That would make sense. This is a workshop after all, right?" Penny chuckled and looked more flustered than he'd ever seen her look. In some twisted way, he was enjoying this reaction from her. "Well, show me how you're going to approach it."

He inhaled, exhaled, and moved in. His lips touched hers again, and after he re-familiarized himself with them, he counted to ten and the French kissing commenced. After initially wanting to recoil in fear when his tongue touched hers-it was just so...wet-he found that it wasn't as terrifying and disgusting as he thought it would be. Actually, it was nice. He felt like he was connecting with someone on a level he'd never even knew existed. As a scientist, he found this situation fascinating. He'd have to write a paper about it or something. As a man, he found it both confusing and electrifying. And he found himself wondering why he'd waited so long to make this happen.

Penny pulled away and smiled at him and touched his hand and Sheldon had to wonder, was all this stimulation coming from the newness of the kissing, or was it because it was Penny he was kissing? Penny, with her cascades of blonde hair and emerald green eyes and she always smelled nice and she cared about him and teased him but didn't make fun of him and it was Penny. It had always been Penny.

"Okay, um, how about biting my lip a little? And use your hands. This is the big one, so make it count." Apparently Penny wasn't anxious to end the lesson, which was just fine with Sheldon.

He moved closer to her again, and they were kissing, and he cupped her face and ran his fingers through her silky hair, and he just nipped on her lower lip a little, not wanting to hurt her, and she moaned. It was a soft moan; she probably didn't even know it happened. But it was music to Sheldon's ears, and he didn't want to stop. kissing. her.

Again, Penny was the one who stopped first. She looked breathless, and her lips were redder than before and kind of swollen and her hair was kind of a mess. He'd always known Penny was attractive; Leonard could never get enough of her, Howard was always hitting on her in that creepy, perverted way of his and Raj always just kind of drooled over her from a distance. So Sheldon was aware of the feelings she caused in men just by looking like...that. But he'd always had control over his baser urges and hadn't spent much time thinking about her in that way. Now the door had been opened. Pandora's Box. And he didn't know how to close it.

"Very good, Sheldon. You are an excellent kisser. I mean, for Amy. Amy will think you're an excellent kisser. I don't-well, you know." Sheldon was not used to this stammering version of Penny. He liked it.

"Well, thank you, Penny. I appreciate the lesson. I feel much better versed in the art of 'making out', as you'd call it. Amy will be pleased with the results, I think."

"I'm sure she will," Penny said. They both regarded each other silently. Things were different now. They probably would be for a quite a while. Sheldon was positive he made a mistake somehow. A mistake that goes back a long time, maybe even more than five years. But that was moot now. For so many reasons.

"Well, Amy's coming over soon, so I guess I better take my leave," he said, unfolding himself from her couch. "Thank you again. I...well, you know."

Penny nodded. And for a second, he was convinced she didn't know. He was probably just making up the part where she felt the same way. That would be something he would do.

But then she says, "Sheldon...you know, if you don't feel comfortable kissing Amy, you don't have to. I'm sure she'll be disappointed, but the important thing is how you feel about it."

And he knew. Sheldon Cooper didn't know a lot about women and relationships and kissing and sex, but he know something about Penny that no one else would ever know. He knew the two of them always had a bond the rest of them never understood. He showed her his whiteboards, she called him a beautiful mind genius guy, and Leonard just watched it happen. Leonard won that round, and a couple more rounds after that. Before now, Sheldon hadn't given it much thought. But he knew now; this thing that existed between them? It was there from the beginning. And it was okay that what they had now was all it could ever be, because just thinking about taking it further than that made Sheldon's stomach hurt with anticipation.

"I know, Penny. Thank you as always for your guidance in matters of the heart. I'll see what happens with Amy. I'm sure you'll get a text describing every single detail of what happens between us tonight."

"I look forward to it," she tried to say sarcastically and instead it only sounded sad. Sheldon turned to leave and had his hand on the doorknob, but turned around and gave Penny one of his rare, patented hugs. She wrapped her arms around him gratefully, and they stood there like that for way longer than was normal or necessary. He kissed the top of her head, thought about saying something, anything...and decided not to. There was a new understanding and neither of them needed to acknowledge it. In an alternate universe, Sheldon and Penny would have made a scorching couple. In this one? Friends.

I totally stole the last line from Singles because I love that movie and I wanted to.