A/N: I may have trampled on some canon here, but once the idea was in my head it wouldn't leave until I wrote it. I have no idea how this is going to go down with people...

It was Anything Can Happen Thursday. As usual, Howard had dragged Leonard and Raj to a bar to seek out desperate, insecure women, leaving Sheldon to opt out in favour of working on his research. Or at least, that was Sheldon's plan. The plan lasted until Penny came home from work, realised her cable had been cut off again and ensconced herself on his sofa with a bottle of wine to watch TV.

Despite his best efforts, he was unable to ignore the endless stream of character info and complex plot details she insisted on sharing with him and finally abandoned his computer to see what all the fuss was about housewives.

"Penny. I don't understand. These women appear to be financially secure, with a strong social support network. Why are they 'desperate'?"

Penny rolled her eyes as she went to pour herself another glass of wine, then frowned as the bottle emptied. She shook the few remaining drops into the still half empty glass and downed it.

"It's about relationships, Sheldon. You know, men and women. All the stuff that goes on between members of the opposite sex when they are actually interested in each other." She looked at him pointedly, but he remained oblivious to her gaze.

"But one of the central characters appears to be deceased. I don't understand. It just seems a very strange premise for a show." Now Sheldon was frowning.

"And I don't understand how you can happily watch people flying round in spaceships with aliens and still think Desperate Housewives is strange." She hiccupped. "Oops." She saw him open his mouth and jumped in first. "And that was not the cue for you to give me your lecture on the science of Star Trek again!" He shut his mouth and narrowed his eyes.

"Very well. But I maintain my position. I don't see the point in watching strangers engage in mating rituals. The attainment of intercourse appears to be the prime objective for most of these characters, to the detriment of all other aspects of their lives."

Penny knew she was crossing a line as soon as the words fell from her lips, but she was irritated with his dismissal of her favourite TV show and, well, the alcohol hadn't helped either.

"Well Sheldon, maybe if you had ever actually 'attained intercourse' you would understand why people spend so much time trying to do it! You have no idea what you're missing and yet you are quite happy to put down anyone who enjoys it! I mean, jeez, you're a 25 year old virgin. Don't you ever think maybe everyone else is right and that sex is actually, y'know, fun, and not some urge to be ignored at all cost..?"

Sheldon waited patiently for her to stop.

"Are you finished?" She nodded dumbly, a little shocked at herself. He looked like he was considering his words carefully.

"Good. Then please allow me to clarify a few things. Despite the fact that I consider the matter is really none of your concern, I do feel the need to correct you in this instance. Whilst it is true I have never had a sustained relationship with a woman, I am not, as you less than elegantly put it, a '25 year old virgin'. In fact, I am neither 25 nor a virgin. I have engaged in coitus previously and despite this I still do not feel the need to devote my life to the pursuit of it. Ergo, your entire argument is rendered unsound."

Penny was very rarely left speechless, but Sheldon's monologue had seemingly dragged all the words from her head. She was aware of a question trying to form in the void, but before it could coalesce the apartment door suddenly swung open and a drunk Leonard barrelled through it. Following closely behind him was Leslie Winkle. "Hey Sheldon, look who we bumped int…oh, erm, hi Penny…" Leonard looked from one woman to the other, struggling to focus on each.

"Hey Dr Dumbass" Leslie grinned. Sheldon's look of confusion immediately turned into a scowl, and Penny decided that this would be an excellent time to call it a night.

"Hey Leonard, Leslie…don't mind me, I was just off…." She stood.

"Oh hey, you don't have to…" Leonard trailed off as he noticed Leslie looking at him pointedly. "Ok, well I guess if you really gotta go…"

"'Night guys." She nearly ran back to her apartment.

Meanwhile, the question had formed and was now burning a hole in her brain. It was still burning when she climbed into bed.

Who the hell had Sheldon slept with?

Penny dreamt that night; the vivid, confused dreams only ever caused by being very, very drunk. She woke with half remembered images; of striking blue eyes impossibly close, of long fingers moving over her skin, of lips and tongues and…well, other things. She blushed and gave herself a mental shake.

Clearly Sheldon's confession had stirred something in her. He was no longer the asexual oddball she couldn't relate to; he suddenly had another dimension to him. A dimension Penny was very familiar with. It was as if two completely different worlds had just very gently collided. Of course, Sheldon himself was no different; the knowledge had changed how she was seeing him, not who he was.

She wondered why Leonard had never mentioned it when they had had those conversations about Sheldon's 'deal'. Was it really possible he didn't know? She just couldn't imagine Sheldon sharing something with her that he hadn't even talked to Leonard about. But then, maybe Leonard had never offered up a theory on his sexuality that Sheldon had felt a burning desire to disprove. She smirked a little. Sheldon couldn't bear not showing off when he had something he could prove.

She knew she should leave it alone, that questioning Sheldon further would probably be futile and would only end in one of them getting exasperated with the other. But the desire to know who chewed inexplicable at the back of her mind. It wouldn't leave her alone. And there was something else.

Penny realised she felt unsettled by the knowledge. Why the fact of Sheldon's non-virginity should bug her was something she struggled with. She decided it was that so many of her assumptions about him had suddenly been undermined; she had thought she had known him and now she realised how little she did know.

Unlike most guys, Sheldon had never shown any romantic interest in her: after she had seen how he tended to view the rest of the human race she had assumed he never showed interest in any women. Obviously though, that wasn't true. But why should that bother her? So what if some other woman had managed to boldly go where no-one had gone before? It was irrelevant, really.

She tried to ignore the chewing at the back of her mind, because she had a disturbing feeling the chewer might have vicious little green eyes, and that wasn't a thought she was prepared to entertain.

Still…Penny decided she had to know what kind of woman could seduce the beautiful mind of Sheldon Cooper.

Purely in the interests of science, of course.