[that’s like … shit, thank you. seriously. sorry, my brain stuttered over reading that, and just keeps stuttering every time, and - thank you. that’s such a wonderful compliment, I needed that]
[Actually had two answers to this, but I went with this one because the other answer would’ve taken place further into the timeline and I didn’t really want to write it with no build up… So hopefully this is okay!]
There are two different Tony Starks inhabiting Avengers Tower.
The Tony who darts across the hallway between his own disarrayed workshop and Bruce’s gleaming, equally disorganized laboratory is the closest version to the Tony Stark he had met on the Helicarrier. It’s the Tony who rambles off scientific jargon at an electric speed that Bruce’s mind joyously chases after, who has to visibly think to pause for breath, who claps him on the back or shoulder with unexpectant affection, who cautiously presents a crack or joke with an expression quivering between a cringe and a smile – it always ends in a smile, because on their floor, in a place where the billionaire seems to be more at home than he does in the rest of the tower, Bruce is quick to snark back in the playful banter that always makes his grin a little less sharp. He’d be lying if he ever said he doesn’t relish in it, the ease his friend is slowly realizing he can have around him, the trust that, though tentative and questioning, is being given to him. It’s a warmth in his chest, really, to realize he’s being considered worthy of it.
But there’s still the other Tony – the one who walks around the team with a mask, who keeps quiet in uncertainty, nervous in company, straight-faced in the presence of criticism.
One day, Clint makes an off-handed comment about Tony dressing his age. The next day, the man is dressing in clothes similar to Steve’s – dress shirts and unwrinkled slacks. So obviously uncomfortable – there’s a line, Bruce knows, between what Tony wears to the office and what he wears at home, a cut to severe one world of responsibility from another of comfort – so obviously willing to be uncomfortable just for the sake of being one step closer to acceptance, like a kid transferred into a new school, looking for a way to make friends, to be liked.
It sets Bruce’s teeth on edge.
There’s a large, dark, pulsating part of his mind that wants to confront this team people that have been invited to live in this luxurious building, who have been provided for to an extent that would surpass even the attentions of the most attentive lover, who use the provisions with the respect they’re due but don’t pause to be grateful or respectful to the hand that has given them … actual confrontation isn’t something he’s particularly capable of, unless it calls for mass destruction of property and life.
Fortunately, he likes the feel of t-shirts.
When Bruce walks into the kitchen for the group breakfast Steve so earnestly insists they have, he’s neither smiling nor frowning, half-focused on the tantalizing smell of fresh pancakes, half-conscious on what he’s doing.
He doesn’t really even notice the staring until he’s already sitting in his usual spot next to Clint, and only then, it’s the old-habit itching of eyes on him that draws his anxious suspicion with the Other Guy’s questioning stir.
“What?” He poses, blinking.
“Um…” Steve drawls, a plate of pancakes balancing in pause in his hands, and Natasha snorts.
“Is that Stark’s?” Clint demands bluntly, eyes dropping from his face to his shirt. At the end of the table, Tony makes an unintelligible, very quiet noise.
Bruce ducks his head to swallow his smirk, eyeing the shirt spanning his chest as he reaches up to turn the music off. The cotton is worn-down in age and wash, gentle against his skin and more comfortable than he had imagined it would be, and while the color is darker than he would normally wear, he’s actually quite fond of the faded print of the Periodic Table it bears.
“Yeah,” he admits, looking up and allowing himself a small smile. “T-shirts are a little more comfortable than button-downs for day-to-day wear. And I think it looks pretty cool.” He shoots an apologetic look to Tony, who is still staring at him in obvious swirling thought. “Sorry I raided your closet. I haven’t really had an opportunity to go shopping.”
“I’ll take you,” his friend promises quickly on a stunned breath. “I know a store. It’s great – great stuff. You’ll love it.” He blinks rapidly as Steve slides the plate of pancakes in front of him. “…Yeah.”
“Thank you.” Bruce keeps smiling.
Later that night, Tony ambles into his lab, chattering a little slower than normal, wearing a familiar Black Sabbath shirt.
Bruce throws back an answer that sets the man off to his usual speed, and doesn’t comment.