Shane: "We lost by 4 goals..."
Paul: "Are you serious!?"
total disbelief or dissapointment in how someone did or said something.
Note: it is a very hard inflection that goes up to indicate the question
Bush: that girl in our science class she's barely average.
Hall: I think she's amazingly gorgeous and makes simpson look ugly?
Bush: Are you serious?
Idiot I'm talking to: Are you serious?
Me: No, I'm just pulling your motherfucking leg. Of COURSE I'm serious!