David Letterman created the CBS institution known as The Late Show, and he hosted it for 22 years before retiring in 22 years. Stephen Colbert is Letterman’s immediate successor, and he’s been hosting the show for seven years now. In that time, Letterman had never been back to visit his old show or his studio until last night. Soon after he finished his run, Letterman said that CBS had never consulted him about picking the next host, and there was some perceived bitterness about that. Last night, Letterman finally made his grand return to The Late Show, where he sat down with Colbert for most of the episode. Letterman had a few requests, and one of them was this: He wanted the National to perform.