Hello Robxstar. You remember the last scenario I dropped for you where Robin throws a birdarang at a supervillain and accidentally cuts off Starfire’s bikini panties?
So imagine he and Star decide to head back to the tower and have excused themselves to Cyborg, Raven and Beast Boy who are off for some pizza. Star, holding her damaged panties up, lets Robin take her back on his R-Cycle. Once they’ve shut themselves alone inside the tower, Robin breathes out in relief that they’ve got themselves away from prying eyes. Right when he turns to Star, suggesting they get her a fresh pair of panties, her cut-up panties go landing on his head. Next thing Robin sees Star smirking at him and doing a casual, suggestive pose with only her tank top and boots still on, but her modesty exposed to him. She teases him over how eager he was to get her naked so soon.
How do you picture Robin reacting?
Probably flames red from neck to ear and goes braindead for a little bit, if it's earlier on in their relationship. (I don't remember if they had been established for a while or not in your last scenario.) If they've passed that awkward stage she might still make him a little flustered but I think he'd get over that quickly and focus on the business at hand, namely, getting her fresh underwear.
He might make a cheeky comment back while he passes them to her though.