Conversation

One thing movies used to do that I liked is having guys who are just, like, buddies, on the same wavelength, in a way that the audience is supposed to recognize but not participate in. Like, the actor with one line says it to another guy who's an extra, and he chuckles, and we realize these guys are buddies and this is an in-joke and we're not buddies with these characters so we'll never get it. Maybe later in the movie one of these guys dies and the buddy is sad about it, or one guy is in trouble and the other is worried. Just having a movie world that has social relationships not organized around the leads