I kind of want to write an Avengers/Brooklyn 99 crossover mostly because I want to write a fic where Steve gets himself arrested repeatedly for unapologetic vigilantism and general shenanigans and the staff takes bets on which Avenger shows up to exasperatedly scold him (Tony is generally the favorite because he always brings lunch with him, but watching Bucky call Captain America a fucking asshole holds a special place in Peralta’s heart.) No one ever wants Pepper Potts to come because they’re pretty sure she’s judging them (they’re right).
DOOOOO IIIIIIIT
Imagine Holt and Bucky in a stare-off. We enter the action to see them already staring at each other silently, and it lasts long enough for everyone in the precinct to notice and for Peralta to speculate about what’s going on before Holt says “good talk” and Bucky says “thanks, you’ve given me a lot to think about” and takes himself off to bail Steve out.
Other possibilities:
Natasha and Rosa bond by wordlessly emptying magazine after magazine on the firing range.
Bruce is feeling a bit Hulky, so Boyle takes him into the breakroom, fixes him tea and talks to him about endives for an hour. It’s very soothing.
Terry and Thor subtly flexing at one another in a bid to establish dominance. (Gina takes pictures).
Jake coming up with increasing elaborate challenges for Clint–”Okay, can you hit a Coke can on a moving bus with one arm tied behind your back?”. Clint starts insisting that they have take turns issuing dares.
Amy makes googly eyes at Steve until it makes him uncomfortable, but once she stops screaming internally they end up having a really thorough and interesting conversation about civil rights law.