I like the idea of Tony wearing very lacy, frilly boyshort panties and Bucky being obsessed with them. He doesn't wear them for any specific reason, he just thinks they're soft and comfortable. Bucky loves the contrast of the fabric and it's color against Tony's tan skin (they're usually light blue or light purple or white)
I’m all for Tony not ascribing to traditional gender roles and gender clothes tbh. He wears panties because they’re cute and soft and they make him feel sexy. It’s a shame that men feel emasculated for wanting to enjoy lace or satin. Tony doesn’t have a problem with it nor does he have a problem with “feminine” colors (lmao they’re just colors and some people can’t even see all of them? Get outta here). And he’s always liked taking panties off his partners, so surely his partners would like taking them off of him, right?
(His biggest regret in life is that, when he was dating Pepper, he didn’t have the chance to get a recording of the high-pitched, startled HNG that burst out of her the first time she saw his panties. Pepper is eternally grateful for the fact that JARVIS didn’t record it because she does not need that held over her.)
((He does, at least, get a recording of Bucky’s loud “BWUH” and then “holy shit” and then “I really did die and this is heaven.”))