Obvious things aside (I obviously don't own Tony Stark, Steve Rogers, or The Avengers), this is a thing that happened.

Steve/Tony now owns my heart, what can I say.

That Time He Touched the Mug

No one was allowed to touch anyone's coffee mugs in the Stark Towers kitchen. It had become an actual, legitimate, official rule: If You Touch My Mug, I Have Everyone Else's Permission To Kill You In My Own Patented Fashion. Each of the Avengers had gleefully outlined their respective Mug Revenge Schemes (Tony had particularly enjoyed Natasha's; very creative use of shattered acrylic)—everyone except Steve, that is, who had left it at a shrug and a "I'd prefer if it were left alone."

And so, Tony found himself in the kitchen at 3:18 in the morning with the cabinet door open, gazing at Captain America's coffee mug. (He knew it was Steve's because A.) he'd seen him drink from it and B.) it was red, white, and blue, and had the fucking stars and stripes all over the fucking place.) Tony's own mug (which was black, sleek, classy, had been a gift from Pepper, and had been slightly altered to include a self-regulating thermometer on the side) was right next to it. It was like the two mugs had been conversing with each other or something (or maybe that was just the sleep deprivation talking, because God knows Tony hadn't slept since like the Jurassic Period).

And now Tony really, really, really wanted to touch Captain America's mug—which sounded like a brilliant double entendre, but which only meant that he actually wanted to touch the cup, not Steve (although the jury was kinda weirdly out on that one, but shh, Tony, shh, people are sleeping.)

Tony stood there, in that exact pose, unmoving (unusual for him) for God knows how long. He knew he shouldn't touch it, knew it was some Breach Of Trust-Slash-Privacy, but seriously, how would Steve even know he'd touched it? He wasn't planning on doing anything to it, but truth be told, Tony had always despised Keep Out Signs, and the whole Don't Touch My Mug system was one giant KEEP OUT sign, so really it was a miracle that he hadn't seriously contemplated this sooner.

With that decided, Tony reached out and soon found Captain America's Really Fucking American Coffee Mug in his hand.

Tony woke in his workshop (typical), facedown on miscellaneous calculations (typical), with Steve's coffee mug in his hand (oh). Oh.

Well, shit.

"Jarvis, you fucker, what time is it?" he mumbled, too groggy to be as pissed as he wanted to be.

"Nine in the morning, sir," Jarvis responded, and Tony could hear the exasperation.

"Shit. …And I'm not in the mood, Jarvis," he rattled off, stumbling to his feet, rubbing the sleep from his eyes, and tripping in the direction of what he hoped were the stairs.

"Wrong way, sir," Jarvis offered helpfully.

"Oh, shut up," Tony shot back. But he changed his direction anyway.

"You're welcome, sir."

"Tony?"

Steve looked surprised to see him, but not as surprised as he might've been two months ago, had they been in a similar situation. Tony took some getting used to—and when people got used to Tony, they got used to insanity. (Fine insanity, though. Perfectly healthy insanity. Unhealthy sanity, even.)

"I may have accidentally touched your coffee mug." He offered it back to Steve without a hint of apology. "…Sorry." (Shut up, Stark.)

Steve took the mug back without a word, and began turning it over in his hands, inspecting it. "So what did you do to it?"

"Do to it? What did I do to it?" Scandalized, Tony put a hand over his heart. "Oh. Cap. You wound me. It was just an honest mistake. In fact, the very insinuation that I would've in any way cannibalized your beloved and so-very-American coffee mug just because I felt like it—"

Steve stopped him with a look. That Look. "Tony." A wry smile. "What did you do? Really?" He shrugged. "I'm sure it's not that bad, whatever it is. Right?"

And just as Tony was about to insist on either his innocence or on his fourth amendment rights, Steve's mug started… glittering. Steve almost dropped it in shock.

Tony gaped.

Steve stared.

The mug was— yeah, it was glittering. From the looks of it, someone ($134,279 to the first correct guess as to who) had made it so that Cap's beloved coffee mug could change colors. It was like one of those mood rings sensitive to heat, except it had only started changing once it had touched Steve's hand. The white stars on the American flag were sparkling like real godddamn stars, and the actual flag looked like it was flapping in some kind of breeze.

"Oh," Steve finally breathed. "Oh."

Tony was still calibrating, trying to figure out when he'd done it. (It must've been some time last night; Tony tended to blackout whenever he went too long without sleep, and he also tended to sometimes, occasionally (usually) continue working when he did. It wasn't a big deal.)

"Er." He didn't know what to say—especially since he'd apparently broken the Thou Shalt Not Toucheth My Stuffeth commandment that happened to be the one rule all of the Avengers had agreed upon. "I'll get you a new one—"

"No." Steve looked up at him, grinning. "Nah, no, this one's still fine, Tony. No, in fact, this is better than fine. This is great." Tony had no fucking idea how anyone got anything done in the presence of such an all-American, white-toothed, really-fucking-charming smile. Through sheer force of will, he expected.

"I—yeah. It was no problem, Cap," he said. "I could do stuff like that in my sleep."