So my friend and I challenged myself to writing a Big Bang Theory/Sherlock crossover, and I'm not one to ignore a writing challenge. Not my best work, and my writing's been feeling off lately, but I tried. The thought of these two sets of characters arguing is absolutely hilarious to me, though when I tried to write it, it didn't come across quite right.

Disclaimer: I do not own anything recognizable.

Ten minutes in and John already had a headache from the incessant arguing.

He hadn't wanted to come to America in the first place, but when Sherlock had threatened to go on his own, John hadn't needed Mycroft's intervening to know how much havoc his flatmate could and would wreak if left on his own. Sherlock's desire to travel across the Atlantic had been sudden, giving John only three days' notice (though, knowing Sherlock, John supposed he should be grateful for even that much) and at first John thought it was fleeting, that it would go away, though he should really know better than to think Sherlock, stubborn as he was, would give in so easily.

There'd been a lull in cases from Scotland Yard, so either all criminals in London had made a unanimous pact to take a holiday for a while, or the higher ups were cottoning on to Lestrade bringing in an outside unofficial consultant and the DI had decided to cool it for a bit until they got off his back. Whatever the reason, Sherlock had been getting restless, and after John hid the gun, he'd taken to stealing John's laptop again, searching the web for cases, because all the ones in his email were dull and simple, and if he had to read through them all he'd 'lose valuable brain cells'.

During his time haunting the internet, he'd apparently stumbled upon some fleeting information on someone that caught his interest – two someones, actually – both in America, and immediately decided he needed to meet them.

For no other reason than to argue with them, John thought bitterly, wearily watching Sherlock do just that in the kitchen with the other man, the one that had caught his interest – Sheldon Cooper, John thought his name was, a physicist or something. Honestly, he'd tuned Sherlock out when he started talking about the man on the ten hour flight to California, only picking up the stray bits of information that managed to sneak into his memory.

"Didn't you say you worked for the police or something?"

John looked over to see the man that spoke to him, the roommate of the one in a verbal sparring match with Sherlock, standing beside him, arms crossed. He looked a bit nervous, though John guessed he was trying not to show it, exuding an artificial confidence that seemed more insecure than anything. Then again, maybe John had just been around Sherlock too much.

"Actually, Sherlock's sort of… well, he calls himself a consulting detective. He helps out on cases for Scotland Yard, while I just tag along and make sure he doesn't get himself killed – harder than it sounds."

"Yeah, I know the feeling," the man – Lester? No, Leonard, wasn't it? – muttered, glancing in the direction of the kitchen with an exasperated look. "Sheldon has that sort of effect on people. Sometimes I think he does it on purpose."

John snorted, and Leonard gave him an odd look. "I know Sherlock does it on purpose. Honestly, he's rude to everybody, and he likes it when they get mad. The thing is, I can't always tell when he's being serious or not; one day he'll reduce someone to tears without blinking, then the next he'll ask me what he did wrong with this look of his…" John shook his head fondly, sighing. "Drives me crazy."

Leonard shifted, an uncomfortable look on his face, and John was starting to worry he'd talked too much – though that was usually Sherlock's problem, not his – when the man lifted his chin a bit in what looked like defiance. But that made it look like –

"Well, Sheldon's not easy to live with either," Leonard said, and in response John struggled to resist gaping, possibly laughing. Was this guy seriously about to argue with him about who had the worst roommate? "He has no sense of personal boundaries, regularly invades peoples' privacy, mainly my own, and he even wrote up a Roommate Agreement. A binding contract! One he regularly refers to if I do something he doesn't like!" He seemed to pick up steam as he went on, while John inwardly rolled his eyes.

"Sherlock steals my gun and shoots the wall when he's bored," he said simply, watching Leonard pause and blink.

The voices in the kitchen were interrupted by Sherlock turning his head to face John and say sharply "One time, John!" before diving back in the argument like nothing had happened, and this time John really did roll his eyes.

Leonard flustered a little before finding his footing again, needing only a glance in Sheldon's direction in order to straighten again, seemingly remembering more evidence to use in his argument. An argument John wasn't all that invested in winning, but was still willing to participate in because he knew Sheldon couldn't have anything on Sherlock, and thought maybe showing Leonard that would help him appreciate his frankly lucky draw on flatmates.

"That's… He really did that? But he's normal otherwise, right? I mean, he doesn't obsess over little things like Sheldon does, assigning specific fridge shelves, thermostat temperatures, game nights – hell, he even has his own spot on the couch! If anyone else sits there, he freaks out, becomes completely unreasonable!"

John eyed him levelly in amusement, letting him get the rant out of his system. He vaguely thought he could sort of understand why Sherlock liked ridiculing and arguing with people so much – now, listening to Leonard complain about his childish roommate, John felt oddly smug and knowing, like he was humouring the man, and he felt a slight satisfaction from it. That probably wasn't a good thing, but again, John blamed the fact he'd been around Sherlock too much.

As Leonard slowed down and eventually finished, maybe running out of things to throw at him, John took a moment to consider how to respond. Really, he had many options to go with – how Sherlock called him away from work and shopping with heart-stopping texts only to tell him something trivial, how he played his violin at indecent hours, how he littered the kitchen with occasionally suspicious experiments… but in the end he decided to go with the simple and glaring choice.

"Sherlock leaves body parts in the fridge."

That stopped the other man in his tracks. Leonard gave him a wide-eyed look, mouth open, utterly speechless, and John took the opportunity to listen in on the two in the kitchen, surprised to hear they were still going strong. By now, Sherlock had usually reduced his enemy to tears or violence, but Sheldon Cooper was still heatedly arguing, with no sign of letting up.

"… it's absolutely ridiculous," he was blustering, face red. "You can't simply look at someone and know everything about them, like their life's written on them like a… a book! Like some sort of superhero!"

Sherlock gave John a sidelong look, accompanied by a smirk that made John wonder if his flatmate had just been waiting for him to pay attention before pulling his trump card in the argument. John thought he knew exactly what that card was, and sighed to himself in exasperation.

"Oh, I wouldn't say a superhero," Sherlock scoffed, turning his nose up at the physicist. "That would be childish. No, what I do is much more impressive – deductions. Every little detail, every scruff mark, every tear in your clothes, tells me everything I need to know about you. Allow me to demonstrate."

"Oh god," John muttered, dragging his head down his face. Leonard looked over questioningly, but he just shook his head in answer, gesturing to the kitchen.

Sherlock had taken a step back, surveying Sheldon and the room around them with a close eye. "Really, it doesn't take a genius to see what you are," he said dryly. "You've made it too easy."

He sucked in a breath and John closed his eyes in preparation.

"Your roommate told John you have a specific spot to sit, that one there, with the pillow – none of the other seats have pillows, and that one's especially large, set in the middle of the seat… so, you use it as back support, though you hardly seem to have spine impairments, so it's habit. Suffer from hypochondria, do you? Your hair is short, so short you hardly need to fuss with it, and I doubt you've changed it much in your life, too resistant to change for that, so it's probably the same type of haircut you had as a child, maybe picked out by your mother. You don't mind arguing, in fact you enjoy it, yet if your mother told you to stop, you'd listen. Your shirt alone tells me more than enough about your superhero obsession, and someone with that level of interest is bound to have a collection of comic books.

"A theoretical physicist, so you're clearly intelligent… young for your field, child genius. I admit I cheated on that one – I Googled you before we came – but the signs are all there, Dr. Cooper. It's just a matter of seeing and observing. Being a child genius carries a feeling of earned superiority, so you most likely lord your supposedly higher intelligence over those who can be considered your friends; I saw how you treated your roommate when we first arrived, so you care very little for their feelings and hold them in low regard. Oh, I like you."

John was slightly surprised Sherlock had left it there; compared to his usual methodical ripping to shreds of people's lives, he'd let this guy off easy. No doubt there were dozens more deductions just begging to be told, but John just prayed Sherlock kept quiet and left things as they were.

Leonard was blinking, looking a little lost, and John felt for him, remembering how he felt the first time he'd witnessed this sort of thing. "It never stops being amazing," he said, patting the man on the arm. "Always annoying, but it never gets old."

"He can't really do that though, right?" Leonard asked, floundering for a reasonable explanation. "I mean, he said he'd Googled Sheldon… so he just learned all that stuff before you came here, just so he could do this little act."

"How much personal information do you think he could find on Google?" Amused, John watched the scientist struggle to find words. "Trust me, it's real. He could do a lot more, too. Be grateful he isn't."

Sherlock and Sheldon were conferring in low voices, thankfully without obvious hostility, and as one they stopped, stepped away, and turned, coming back to their respective roommates.

"Leonard, I like him," Sheldon stage whispered.

Sherlock just gave John a smug smile, turned away from their hosts, and John couldn't resist returning it with a grin of his own.

"Mr. Holmes," Sheldon said, turning to face the detective. "I would be honoured if you would consider teaching us the art of deductions. I promise I'm a very quick learner, though I can't say the same for Leonard."

Sherlock considered for a minute, though John knew he was pretending – no way would he be able to turn down the chance to show off again – and John wondered if they would ever be able to leave. Judging from the look on Sheldon Cooper's face when Sherlock agreed, John doubted it.

I love both Sheldon and Sherlock, and there isn't an decent amount of crossovers for them on this site. This might not be the best contribution, but it was still fun to write.

Reviews are awesome...?