Not technically an extra, but there's a guy in Jaws in the scene where the fishermen have a shark they caught hung up on the dock. Richard Dreyfus says something like the latin name for the species and the guy says "a whaaat??" in a very high, soft, gladly pay you next tuesday for a hamburger today kind of voice, and then 30 seconds later they cut back to him and he's like an 80s cabbie stereotype: "Don't give me this bite radius crap, Stick your friggin head in there."

Gets me every time