Jumping the joke
When several people are listening to someone tell a joke and one idiot decides he needs to laugh out loud before the punchline. We all have at least one friend we know that is notorious for jumping the joke.
Dude: ''Look at Tom with that huge dumbass smile on his face.
Guy: ''You know exactly what he's up to. He's jumping the joke in T minus 10.
Guy: ''You know exactly what he's up to. He's jumping the joke in T minus 10.