I don't know, this is such a tough competition! I don't know if it's fair because not every butt in the butt kingdom is represented but there are some good ones. OK, great ones. Why are animal butts the very cutest of all butts? Chew on THAT.
Also, this reminds me very much of the Bob's Burgers butthole episode, aka the BEST 22 (?) minutes of television ever written and then animated then shot and then aired:
I'd also like to point out that I know that rabbit's butt in real life! In fact, I know the entire rabbit! His name is Nibbler and he is very special and crazy. Here's a video of him throwing stuff like the mad man that he is, and it's hilarious. The world is a messed up place, sometimes you just have to throw some shit around! Get angry, Nibbler!
Who Has The Cutest Bottom in the Animal Kingdom? [Neatorama]