Like him or not, it's no secret that Barack Obama is one telegenic cat. Given the amount of political soap to sell and the politicians who need to sell it, it shouldn't be a surprise that Obama has been on 'The Late Show with David Letterman' five times. But Monday night's episode is a big deal because it is the first time in 'Late Show' history that a sitting president will be a guest. Yep, President Obama will visit Dave for an hour and yuk it up about health care. Here's hoping we won't need an aspirin afterwards ...

To mark the occasion, here's a list of stand-out Political Moments in Late Night.

McFeud

David Letterman can be a prickly pear sometimes. Make that most of the time. And what pisses Dave off is when a guest for his TV show doesn't show up. But what makes him even more ornery is when the guest scheduled for his show winds up being interviewed somewhere else. Ladies and gentlemen, the runner up for POTUS (President of the United States) ... John McCain, a.k.a. The Man Who Wasn't There.