"Tony?"
"What?"
"What are you doing?"
"Something important, leave me alone."
"I have a right to know what you're doing, since I saw you sneak into my room earlier and grab my pants."
There was a thick silence as Tony stopped his tinkering, lifted his mask, and turned to Bruce.
"You saw me? I thought I was being really covert there." "Well, you weren't." "You're sure you didn't just imagine it, maybe it was Loki." "I have a feeling Loki has better things to do than steal my pants." "And I don't?" "Not really, no."
There was silence again, and Tony finally sighed, rubbing some soot off his cheek. "Okay, big guy, you caught me. But I took them for a reason." "It better be a good reason." "It is. You know how you hulk out and stuff?" "No, Tony, I hadn't noticed." "Anyway, it seems like, ya know, kind of uncomfortable to be walking around in ripped pants all the time when you're Mr. Big and Green, everything threatening to pop out at any second-"
Bruce sighed, and rubbed his temples. "Your point, Tony?" "Yeah, well, me being the great, generous and equally brilliant person that I am, I developed a new pair of pants for you." Bruce raised a sceptic eyebrow, and Tony gestured to the work table. "Look, see? They stretch when you grow, and adjust to fit your enormous waistline! I call them… Stretchy Nano Pants."
Bruce stared for a second at the newly-finished pants before him, wondering if he should be thanking Tony or asking him how he thought of the name.
"You… only you," Bruce finally said, shaking his head. "You'll love 'em once they're on. Just, make sure you wear them in a stressful situation, like, in line for a really busy Taco Bell: Stretchy Pants! Swimming in a crowded wave pool: Stretchy Pants! Oh, and also, it has a built in air conditioner, so the tightness of the microfibers doesn't bother you."
Bruce swallowed, and laughed a little as he looked back and forth from the pants to Tony. "Th-thanks, I guess?" "No problem, Big man! Now go try them on!" "I-I don't think s-" "Come on, just for a minute!" "No, Tony, I'm busy-" "I just made them Bruce, try them!" "I don't want to!"
Tony yelped as Bruce's temper got the better of him.
"HULK SMASH STRETCHY NANO PANTS!"