My biggest pet peeve are just girls who go to sports bars who have no intention on caring what teams are playing, like they're looking for just a night out. That drives me more crazy than anything else. Like, don't pretend to be a sports fan.
Look at the Coen brothers. All their minor characters are as interesting as their protagonists. If the smaller characters are well-written, the whole world of the film becomes enriched. It's not the size of the thing, but the detail.