Now that David Letterman is retiring, there’s going to be no end to the “Top 10 reasons David Letterman is retiring” jokes. Credit CBS News’ Mark Knoller for being one of the very first. Let’s have a look.

10. Running out of stupid pet tricks.
9. Chris Christie will be thin by then.
8. Wants to host the Oscars just one more time.
7. To win a bet with Jay Leno
6. His last chance to be a subway motorman.
5. They keep his studio too damn cold.
4. Agreed to teach Broadcasting at Ball State.
3. Drew Barrymore won’t flash him anymore.
2. Tired of being pooped on by Jack Hanna’s animals
1. He’s not. It’s just a negotiating ploy.