Seven Guest Stars Who Blew Our Minds on The Big Bang Theory

Charlie Sheen! Stan Lee! Bill Nye! Watch our favorite surprise celeb moments from the series

HOWIE MANDEL

To infinity and beyond! It's a very underwhelming welcome back to Earth for Howard on episode 4 of season 6, when he arrives at the airport after a trip to space and finds out the paparazzi aren't screaming "Howie!" for him – they're screaming for Howie Mandel.