 DATE: In the scene in which Andy and Jerry Lawler appear on  television with David Letterman, Letterman was working for NBC. The  scene, however, was shot in the Ed Sullivan theatre (notice the  spiral staircase when Andy runs out the door,) which Letterman  didnt begin filming in until he signed on to work for CBS. Whats  more, Letterman wasnt wearing his glasses during the original  filming of the episode.