Tony didn't expect a harmless bit of flirting to go as far as it did. After all, he flirted with Bruce near enough everyday in the lab and neither of them thought anything of it – innocent fun.
Although, they'd both be lying if they said they weren't… interested in what was potentially on the table, and Bruce was fairly sick of his several year long dry spell.
Bruce had been shoved harshly against the lab wall, his hands knotted in Tony's hair as his tongue rolled along Bruce's stubble rough neck. A series of short, desperate gasps escaped through Bruce's lips and his grip on Tony's hair tightened; sending waves of pleasure through them both.
It had been years since Bruce had any positive human contact; it was ridiculous how much he wanted and needed this right now.
Tony's hands slid down from Bruce's neck, to the small of his back, and down again to cup his ass. When Tony lifted him up, he took the initiative and wrapped his legs around his waist, pulling him impossibly close and drawing a low groan from the other man's throat.
Tony pulled away and gasped sharply, "You sure you wanna do this, big guy?"
"Never been more sure of anything in my life," Bruce pulled Tony in by the shirt collar for a mad, violent kiss. Their tongues explored each other's mouths as Bruce undid Tony's shirt buttons as fast as humanly possible with shaky fingers. He shrugged the shirt from his shoulders and settled a hand over the arc reactor. Bruce was intrigued by the arc reactor; it haunted his mind how something so spectacular was now a permanent part of his friend's body.
Suddenly, Tony pulled away roughly, dropping Bruce to the floor with a painful thud. He looked up from where he was now perched against the wall and heard Barton's unmistakable sniggering.
"Well, Clint, I guess I owe you ten bucks," Natasha had her arm entwined with Barton's. He was doubled over in a fit of uncontrollable laughter by this point whilst Natasha looked on slightly embarrassed for the pair they just interrupted.
Tony offered a hand out to Bruce and pulled him up; he leant on Tony, still out of breath and flushing bright red – from both embarrassment and from having all the air drawn from his lungs when he fell. "There better be a damn good reason why you're in our lab right now…"
"There's a debriefing. Although what you were doing looked about fifty times more fun." Natasha answered, her voice surprisingly smooth.
Barton wiped a tear from his face, yep, he was crying with laughter, "I mean, we could always tell Fury you're busy in here – which, yeah you kind of are?"
"Yes that would be fabulous, now if you could close the door on your way out, that would be super." Bruce replied with a smirk, waving them out of the lab. When they had left – Clint laughing almost as hard as was before and Natasha giggling like a schoolgirl – Bruce locked the door with an audible click and with the lust back in his dark eyes, grinned evilly at Tony. "Now where were we?"