You may know that in the 80s, Martin Scorsese directed Robert De Niro in a movie called The King of Comedy. It's the story of a comic so desperate to get on television that he kidnaps a Carson-esque talkshow host (played by Jerry Lewis after Carson declined the role) and refuses to release him until he's given a slot on the show.
But did you know that the film's screenwriter, Paul D. Zimmerman, who wrote the script in 1973, then called The Late Show with David Letterman asking for a slot? Letterman's producers agreed as long as Zimmerman's was willing to do some stand-up. As the Lewis character says in the film, "You don't just walk onto a network television show without any experience." It goes about as well as you'd expect. Stick around until after the credits for a bonus.