Funnyman Stephen Colbert, left, takes a selfie with David Letterman on the "Late Show with David Letterman" on Tuesday, April 22. It was Colbert's first visit to the show since CBS announced <a href="http://www.cnn.com/2014/04/10/showbiz/gallery/stephen-colbert/index.html">Colbert would succeed Letterman</a> when Letterman retires in 2015.