Jon Stewart
Jon Stewart Jokes with David Letterman CBS

It's easy to forget when comedians do bad things. That's the case with David Letterman, whose career was once shrouded in scandal. In 2009 Letterman was blackmailed into confessing his affairs with young interns. However, the controversy has since subsided and the late night host seems to be at the top of his game. Even Jon Stewart failed to recall Letterman's folly when he appeared on the 'Late Show With David Letterman' Wednesday (Feb 15).

When the two joked about Mitt Romney and compared him to an underwear model, Stewart quipped: Do you even have to wear underpants? I would think at this stage of your career, you have people who could just sit there and hug your groin for you. He even referred to someone getting college credit' for doing so.

This prompted Letterman to reply, Jon, I had a little trouble along those lines, alluding to his pubic admission of adultery two years ago. Midway through the bit, Stewart realized he was on sensitive ground and pulled back. The hilarious interview concluded with Letterman giving Stewart a pencil to play with.