I was playing Pokemon at the local Cardshop whilst waiting for a match and some of my friends crowded around to see. We're all a bunch of DC fans too and my rival said in the middle of it: "Why so serious?"
Everyone jumped up and either laughed, yelled, or rage faced. One of my friends hit his head on a table saying: "Why?"
Favorite response: "IS HE THE FREAKIN' JOKER OR SOMETHING!?"
Not really a mishap for me as I kicked my rival's butt but the guys were laughing their heads off for the rest of the day.