Who dat?

Who dat? is an alternative pronunciation of the question "who's that?"

Originally popularized on stage in vaudeville, starting in the late 70's to the early 80's has become a chant of team support. It is most widely used by fans of the New Orleans Saints, an American football team. The entire chant is: "Who dat? Who dat? Who dat say dey gonna beat dem Saints?" "Who dat" may also be used as a noun, describing a Saints fan.