people that take quotes/slogans and overuse them by changing them ever-so-slightly. for example "got milk?" has been used for just about anything you can think of: got art? got fleas? got Guv? got green? got Freud? got justice? got homophobia? got ADD? Yea, I got one for you...got creativity?
and I'm sorry to say, but "why so serious?" is on its way to becoming the new "got milk?" why so bitter? why so stupid? why so bad? etc.