Title: The Necessity of Chaos

Disclaimer: I do not own TBBT or its characters and I make no profit from this, it's all for fun.

Spoilers: Probably through early/mid season 4 – up until Amy, at least.

Pairing: Sheldon/Penny

Author's note: I don't know how Amy's storyline ends on the show, maybe it already has (I'm behind), but in the world of this story, she and Sheldon are currently friends.

XXXXXX

It had been a long day at work, and the last thing she expected to see when she entered her building was Sheldon sitting in the stairwell, typing something on his computer.

"Sheldon?" She asked, as she got her mail, shuffling through the stack of envelopes. Bills, bills, and more bills. She was tempted to throw the entire lot into the trash. "Is there a reason you're sitting on the steps? Did Leonard kick you out again? I'm going to talk to him –"

"No, it's not that," he said, as she stopped midway up the first flight of stairs. "I chose to leave, it was better than spending another moment with Leslie."

"Leslie's over?" Penny came back down to sit next to Sheldon at the foot of the steps, against the opposite wall. "She and Leonard are back together?"

"No, thankfully she hasn't pulled him back into her vortex of evil. They're working on a project together. I didn't ask what because...I don't care."

"But why are you sitting down here?"

"I was waiting for you," he said, as he started closing applications on his laptop. "I was going to seek sanctuary in your apartment, but you weren't home."

"Really?" She was surprised that he'd wanted to come over. They hadn't spent much time together in the past few months. It had been several weeks since she'd seen him other than occasionally passing each other in the hall or lobby. He'd even been absent the last few times the others had come to have dinner at her work.

"Why do you seem surprised?" He asked.

"I haven't seen you in weeks."

"You see me right now."

"Sheldon," she complained, really not in the mood to argue with him tonight. "You know what I mean. Ever since you started seeing Amy. Or not seeing her. Or whatever you two call it."

He'd actually noticed that, as well, and he'd been thinking about it for a few weeks. In the beginning, he hadn't really been aware that he'd stopped spending time with Penny as a direct result of becoming friends with Amy.

Then, when he had realized it, he'd found it was nice with less of Penny in his life. It wasn't like he outright banned her, and she was still friends with all of them, but she purposely avoided coming over when Amy was at his apartment. Gradually, he saw her less and less. The more Amy was around, the less Penny was there. His life was more orderly, and made more sense. He didn't have to deal with Penny showing up whenever she felt like it, or complicating his life in the aggravating way only she had perfected.

Yes, things had been fantastic. Until one day, he realized they weren't anymore.

"It's not my fault you don't like Amy," he told her, feeling quite defensive for some reason, maybe out of guilt. Though that should be impossible.

"Amy's not exactly a fan of me," Penny shrugged. "She's made it no secret. Sorry if I don't feel like having my life picked apart by her, for the both of you to laugh at."

He glanced over sharply. "Is that what you think?"

"I don't think it," she said bitterly. "It's pretty obvious."

"I don't feel that way," he insisted. "I thought teasing your friends was an acceptable, even expected, part of all friendships."

"There's a difference," Penny said. "Amy and I are not friends, so when she does it, it feels more like an attack than anything else. But you know what, I don't even care, because that wasn't my point."

"What was your point? Because I feel you lost it a long time ago."

He always had to make everything so hard. If she hadn't known him as well as she did, she'd have thought he did it on purpose. "I never see you, that was my point. I guess I kind of…missed you." When he didn't say anything, she scowled at him. "Clearly it was one-sided."

She was about to stand when his voice stopped her. "It's better this way, don't you think? Amy and I are much better suited to be friends than you and I."

She stared at him in disbelief. "Sheldon, she's a female version of you. How is spending time with her…fun?"

"I enjoy spending time with myself," he pointed out. "Therefore, it would be obvious that I enjoy spending time with her, too. You and I have different definitions for the word 'fun'."

She flipped through the envelopes in her hand as she thought about that, before smiling at him somewhat sadly. "You and I have different definitions for everything."

He shut his laptop and stared at its cover, wondering how to explain to her what he was thinking. "Amy makes sense. She thinks logically. She bases her view of the world on scientifically proven facts. You base yours on emotions."

Penny thought she might finally be starting to get it. "You understand her, which means she's safe for you."

"I guess that's one way to put it," he reluctantly agreed, though he still felt she was missing something.

"And I'm not," she whispered, but it was so quiet he thought she probably hadn't meant for him to hear her.

"I can't predict you. I've never been able to," he said. "And believe me, I've tried."

"Is that supposed to make me feel better? I thought we were friends," she allowed her anger and hurt to show, which she normally never would have. But if this was going to be the end of their friendship, she figured it didn't matter anymore. He should see how much he'd hurt her, even if (as she suspected) he didn't care.

"We were – we are friends. However, in the past few weeks, I've been wondering, if maybe there's only room for one female friend in my life. Therefore, it makes sense that it should be the female with whom I have the most in common. The one who understands my work, and who thinks in a precise, logical fashion."

Penny had certainly been told a few times in her life that she didn't measure up, but she'd never heard it in this way. It had never felt so heartbreaking before, either. "You can stop, Sheldon. I get it. If that's what you want, then I'll respect your wishes."

"Penny –" he began, but she stopped him by moving to stand in front of him, where he still sat on the stairs, laptop in hand and a look on his face she might describe as…lost.

There were plenty of things she wanted to tell him: That he was an idiot for thinking he could have only one female friend. That it was terribly unfair he'd cast her aside for what essentially amounted to his female clone. That it hurt deeply that he'd measured her and Amy side by side, and found her lacking. That it had taken a few weeks of barely seeing each other for her to realize that he'd been one of the best parts of her life, and she more than missed him. That she thought she might have been incredibly stupid and allowed herself to fall for someone who not only didn't want a romantic relationship with anyone, but didn't want to even continue a platonic friendship with her.

That maybe she was the one with the problem, and not Sheldon, because he'd never been anything but honest about who he was. And she couldn't fault him for being who he was, especially not when who he was…was someone she loved.

She didn't know what possessed her to lean forward and kiss him. Probably the thought of losing him completely – which it seemed had happened anyways. Her kiss was light and chaste; to her, it felt like goodbye. To him? She didn't know for sure, but she did know that when she pulled back, he leaned forward to try and keep her there – which made her eyes snap open with a new realization that she might have gotten everything completely wrong.

She scrambled backwards a few steps, leaving him in the stairwell, and really had no idea what to say to him.

He only watched her, as if she'd just proven something fundamental in his universe. "That…do you understand now? I can never see you coming."

"Sheldon? Penny? I see I'm interrupting you," Amy said, from the doorway to the lobby, and Penny had actually never been happy to see the other woman, until that moment.

"Uh, no, you're not. I was just going," Penny said, sprinting up the stairs before Sheldon could say anything more. In hindsight, it probably would have been helpful if she'd stopped around the corner to eavesdrop on him and Amy, but she'd really been in a hurry to get out of there. Besides, she had a fairly good idea of what they were going to say.

XXXXXX

It had taken less than five minutes for him to explain to Amy what she'd seen, or thought she'd seen, between him and Penny. It also proved his point that Amy was a much more logical choice for a friend, since she made practical, realistic observations and he countered them with his own explanation, which she'd readily accepted as the truth, because she knew he had no reason to lie to her. She would never let emotions cloud her view of things.

He told her he had a few things to take care of, and he'd talk to her more in depth at a later time, to which she'd agreed and left. Whereupon he found himself upstairs, knocking on Penny's door.

She didn't answer.

He was forced to give up and return to his own apartment. Thankfully, Leslie had already left; she'd passed him and Amy in the lobby.

"Has Penny been here?" Sheldon asked.

"No, was she supposed to be?" Leonard shrugged. "I actually haven't seen her in days, now that you mention it."

Sheldon sighed in frustration, wondering if she'd ignore him if he called her. "Never mind, I'm going to bed."

"What? Now? It's five o'clock!" Leonard protested. "The others will be here soon for movie night."

"I'm tired, good night." He ignored his friend's arguments as he entered his room, stopping short when he saw he had a visitor.

"Hi Sheldon."

He kicked the door shut behind him. "Penny."

"Please don't start with the 'you can't be in my room' speech," she said quickly.

"I guess you know me too well," he said, thinking it was cosmically appropriate that she'd know him, while he still seemed to not know her at all. For some reason, he found himself smiling at her despite that. "I didn't predict this, either."

She pulled at the edges of his comforter nervously. "Sorry."

He narrowed his eyes at her. "How did you get in here without Leonard seeing you?"

"He's not exactly a detective. I walked by him while he was in the kitchen, arguing on the phone with Raj."

Sheldon nodded and came over to sit on his bed. She immediately jumped up, knowing she'd have to speak quickly before he regained himself and ordered her out of his room, and probably his life, for good.

"I've been thinking, Sheldon, and it has nothing to do with tonight. This is something that's been a long time coming. I like having you as a friend, and I thought you felt the same way. I see, now, that maybe I haven't been what you needed, so I'd like to make a proposition."

"You?" He raised his eyebrows. "You're making me a proposition?"

"I'll try to be more like Amy," she said, as she paced back and forth across the length of his bedroom. "I mean, we could make a schedule of times we saw each other. I'll never drop in out of the blue. I'd be more predictable. That's what you want, right?"

He didn't say anything and she watched him with apprehension. Part of her couldn't believe she was making such a crazy suggestion to him, but another part of her missed him too much to stop it. If he hadn't sort of kissed her back, when they were down in the lobby, she never would have bothered with this plan. But she'd decided that his actions meant he must miss her, too.

What it came down to was that she'd rather see him occasionally, and maintain their friendship, than be out of his life for good. And if it meant changing to make him happy, well, she would at least try. Because it beat the alternative.

"You could make a schedule," he agreed. "But that wouldn't change the way you think. You're a very emotional person. You'll never be like Amy – rational, logical, predictable. Surely you must know that."

Her shoulders fell, because she hadn't considered that part of it. "I could make an effort to be more…logical. To not base everything on emotions. Let me at least try."

She watched him hopefully, and it took only one instant for him to crush her hopes.

"No," he said simply. "I won't let you try."

"Oh," she whispered, crossing her arms. "Okay. I guess it wasn't the best idea anyway. I could never be Amy."

"No, you couldn't," he affirmed, and she bristled at the amusement in his voice.

She hated herself, at that moment. For believing that he might accept her attempts to change. That he might value what they'd had enough to let her try and save it. Obviously he didn't. He had Amy now, and that meant he didn't need her – not in any way.

"I should go," she said, feeling like an idiot for even coming to his room in the first place. She'd only…she'd wanted to try and keep him, and even thinking it made her realize how absurd it was. You couldn't hold onto somebody who wanted you to let go of them.

"That's it?" He asked. "That's what you came here for?" He'd made himself comfortable leaning against his headboard, hands folded and legs neatly crossed. He was the picture of contentment, and it infuriated her.

"What do you want from me, Sheldon?" She yelled, realizing too late that Leonard might have heard her from the living room. "I offered to change for you and you didn't want that. I see now that what you want is for me to be out of your life, so…fine. That's what I'll do." She turned away from him, resting her forehead against his bedroom door to try and compose herself.

"I never said that," he told her quietly, from too close behind her. She whirled around to find him standing inches away, when she hadn't even heard him get up.

"You're right," she said furiously, as he backed up toward his bed with every step she took nearer to him. "You didn't say anything. Nothing! Except to basically let me know that Amy is better than me, in every way you could ever want. She'll be the perfect friend for you. And us? You can just forget we ever knew each other, since that's what you want."

"Amy is perfect for me," he agreed. "That's one thing you have right."

She couldn't believe that he'd be so arrogant, especially in the wake of her obvious anger. She lashed out, pushing him backwards, and watched in triumph as he landed on his bed, staring at her with a mixture of shock and confusion. "I hope you're very happy together."

She turned to leave, when he grabbed her arm and pulled her toward him. She lost her balance and couldn't catch herself, landing on the bed next to him. "What the hell?" She was shocked that he'd reached out to touch her.

"When we were in the lobby, you left before I could explain," he told her. "I'm not going to let you leave again, not until you hear what I have to say."

She wrenched her arm out of his grip. "Spare me your words about how perfect Amy is, because I don't care."

"She is perfect," he agreed, as Penny grit her teeth and seethed. "She's logical and predictable, rational and reasonable, and –"

"Shut up, Sheldon!" Penny yelled.

For once, he seemed unfazed by her anger. "And you're the exact opposite. You're illogical, unpredictable, irrational, unreasonable –"

"I don't hear anything in there that makes me want to stay," she fumed.

"You are my chaos," he whispered. "I don't know what to make of you."

Irrationally (and wouldn't he expect that) her mind stalled on the word 'my'. What did he mean when he said that she was his chaos?

"I'm sorry," she told him, as a reflex, though even as she said it she wondered why she was apologizing to him, still, for the dozenth time that night, simply for being who she was. He should be apologizing to her, for finding someone better to take her place. "Sheldon, I told you I'd change, that it was worth it for me to keep our friendship even if it meant becoming more like someone you could predict. You didn't care."

"Because I don't want that," he said, vehemently.

"Then what do you want?" She asked, her anger fading, and turning into resignation. "Maybe you're right, I shouldn't try to change, what kind of basis would that be for a friendship? If this doesn't work for you," she gestured to the space between them, "then that's the end of it. We are who we are."

"I like who you are," he told her. The words were so unexpected that she wouldn't have been able to reply even if she'd had a coherent response.

He took a deep breath, and his frustration fascinated her. "Penny, I don't know if you're aware, but not much surprises me."

"Yeah," she said, wondering why he was stating the obvious. "I've noticed."

"You surprise me."

"I told you I was sorry about that."

"It's not something to apologize for," he told her. "I have analyzed you in hundreds of ways. I've created entire algorithms to figure you out. It's futile. I can't do it. Every once in awhile I'll get something correct, but most of the time I can't." He sighed heavily. "You should know that…I don't want to stop trying."

"You like who I am," she said, reiterating his words from a few moments earlier.

"I don't want you to change," he said. "I have identified one constant about you, though. Aside from your general unpredictability."

"Yeah?" She leaned forward.

"You're there for your friends when they need you. You're there for me when I need you. That should serve as a fairly useful gauge for determining your future behavior, but still, your choices often elude me."

"And you like that?" She asked.

"For lack of a better word," he said, pausing for a moment, obviously uncomfortable, "I…love that."

She swallowed and reached out to tentatively touch his arm. "Please tell me this means you aren't trying to remove me from your life."

"I would never do that," he said swiftly, meeting her eyes. "If you'd stayed in the lobby, then you'd know this already. Penny…you kissed me earlier."

Right. She'd been hoping he'd forget about that, but Sheldon would probably never forget about anything. "I'm sorry for that. I don't want it to change us, or our friendship. I was upset because I thought you were trying to get rid of me, and I wanted to say, well, goodbye."

"And now?" He asked.

She tilted her head, trying to read him, and failing in the way she imagined he must always fail at trying to read her. "What do you want?"

"It completely shocked me when I came to this conclusion several weeks ago," he told her, "but I find that I want…you."

"As a friend."

"As more than a friend."

"More than a friend?" She asked, hardly believing it.

"I don't know why, or how," he admitted, "but as far as I can tell, from what I know of romantic relationships…yes, that is how I want you."

"Why?" She asked, well aware he might not be able to give her an answer, but wondering anyways.

He studied her face, unsure if he could explain it in a way she would understand, especially when he barely understood it himself. "In a world of constants, where I know how most people will react to any scenario, I still don't know you. I told you earlier that you surprise me, but it's more than that."

"What do you mean?"

"You challenge me, Penny."

How did he make that sound like something fantastic? "That's a good thing," she said, purposely not making it a question.

"It never used to be. I don't know why, with you...it's a very good thing," he told her, barely stopping himself from lunging off the bad in surprise when she threw herself at him, hugging him as tightly as she could. And then she kissed him again, but differently from the way she had downstairs in the lobby.

She was still tentatively careful, not wanting to scare him off, but this kiss was most definitely not a goodbye. Far from an ending, this kiss felt like a beginning – to both of them. When he kissed her back, she couldn't help grinning against his mouth before pulling away.

"I didn't predict that either," he murmured.

"Sheldon, I think what you're trying to say is that I bring color to your life."

He rolled his eyes at her sentimentality. "If that's how you want to put it, then fine."

"What did you tell Amy in the lobby?" She asked.

"I told her that I had room for one female friend in my life, and that if she wanted, the spot was hers."

Penny inhaled sharply. "What?"

"She accepted."

"Then what –" Penny didn't know how to go on.

"You and I are more than friends, are we not?" He asked. "At least that was the impression that I –"

"We are still friends, Sheldon," Penny informed him. "You can have more than one female friend. You should be friends with Amy if you want to. And yes, we could be more than friends if…you want."

He smiled at her. "See, I thought you would order me to cut off all contact with Amy Farrah Fowler. Once again, you surprise me."

"And it's not a bad thing?" She questioned.

"No…it's not. I don't know how to explain it, except that I've missed it the past few weeks. I've missed you."

"I missed you, as well," she told him. "I may just love you, too."

He leaned back against his headboard and stared at her for a minute. "I didn't see that coming, either," he finally told her. "Sometimes I think I could know you for fifty years and still be unable to predict you."

She only laughed. "Are you willing to test that theory?"

The way he looked at her told her that he'd actually considered it with a seriousness she only joked about. "Yes, I am," he said. Then he kissed her again.

"Why?" She asked, when he pulled away.

"Because…I love you," he said, confused, and wondering how she hadn't seen that by now.

She blinked at the admission. "I may surprise you, but you can still surprise me, too," she said. When he only shook his head and took her hands, she grinned. "Want to go surprise a few more people? I think Raj and Howard are here for movie night, by now."

"If you want," he agreed, though he secretly looked forward to their reactions of disbelief.

"I very much want," she smirked.

And they did surprise the others – somewhat. Simply telling them wasn't enough, as Howard declared it was "completely unrealistic," and Raj said (via Howard) that it was "the worst practical joke ever." It had taken a demonstration from Penny for them to actually believe it. After that, Raj had admitted that Sheldon would never go so far as to actually kiss someone for a practical joke. Though it was equally as strange for him to do it for any other reason - but they were insistent, so he believed them. (Truthfully, even a year later he still wouldn't have been entirely shocked if the two of them announced it had all been a prank).

Penny had been most worried about what Leonard would think, but when they had a conversation later, he was surprisingly fine with it. Maybe part of that had been a lie, at first; she'd never know. What she did know was that he got a new girlfriend a few months later, and after that he seemed genuinely happy.

Howard took it upon himself to trace the path of their entire relationship, going so far as to interview their respective friends and family, to determine how it was possible that the two of them had come to be in a relationship. He spent months on it, to the point that Penny was seriously concerned about him, until one day he gave up, declaring he would never find an answer.

"It's not that confusing," Penny said. "I've told you before, Howard, many times. You don't listen to me. Sometimes people who are opposites find they work well together."

"Yeah, but Sheldon? Sheldon?" Howard sighed. "Why couldn't you have discovered that you loved me?"

She shrugged. "Because you're not Sheldon?"

"Thank God for that," he muttered, slumping further into the couch as she patted him on the knee.

"I've told you before," Sheldon said, as he handed Penny a drink and motioned for her to slide down on the couch. "She's unpredictable."

"Since when is that a good thing? Besides, I still don't get it," Howard insisted. "How is being 'unpredictable' a reason for getting together? Really, I want to know, because if it's a good pick-up line I'm going to use it on women from now on."

Penny laughed and glanced at Sheldon. "I don't think it will be as effective as you hope, Howard."

"Why?" He demanded.

"I can't explain it," Penny said.

"You guys are useless," Howard complained.

"Sorry, Howard," she shrugged.

"Are you really?" He asked suspiciously.

"No," she smiled.

"I knew it," Howard complained. Penny leaned against Sheldon's shoulder, and Howard was surprised - not at her actions, but at the fact that he no longer found it surprising, because they did it so often that he was used to it by now. Here he was, still searching for answers to something he was sure he'd never see as normal, and somehow, along the way, he'd come to see it as normal.

It was then that he realized it didn't matter whether he knew why they were together or not. They were happy, and he could accept it – even if he'd never understand it.

XXXXXX

The end! I hope other S/P fans enjoyed it. =)