David Letterman bans Harvey Pekar from the show
Although you may not recognize the name Harvey Pekar, he was once big news, having authored a successful comic book series called American Splendor, which was later adapted for film. Pekar went on Letterman's show several times, during which it was fairly obvious that the two men didn't get along. In 1988, things became heated between the two, and Letterman informed Pekar that he would never be invited back on the show, calling his comic a "Mickey Mouse magazine."