When a dumbass with no sense of humor explains the funny right out of a perfectly good joke.
Guy#1: Did you know that Mike Tyson is to appear in the next Batman movie?
Guy#2: Wow, no I didn't.
Guy#1: He's the Nibbler!
Guy#3: That is a reference to Mike biting peoples ear.
Guy#1: Thanks for the explain-rape, guy#3.