In Cata we picked up a random 5th for arena. The other four were all IRL friends in skype, he refused to get in skype but insisted he was an incredible player.
After one game, it became evident he wasn't and we dedicated the rest of the evening into trolling him.
One of my more memorable trolls after killing a player in an arena match I typed "/p OMG I looted |Fangs of the Father| from that rogue's body!" - the rest of our arena matches, every time we got a kill he'd be clicking the bodies trying to get loot while we laughed hysterically attempting to finish the match. To my knowledge, he never learned that he was duped...