Have you seen the commercial for Sonic that the two guys are talking, and the one says "jenna said what" in response to "Je ne sais quoi". It gets me every time, and then that phrase is in my head for the next few hours! The next saying that will be in my head is clubman pinaud... only because pinaud is fun to say. I have no clue as to what this means, but saying it is fun.
What other sayings once you hear them, get stuck in your head for the rest of the day?