Zookeeper "Jungle Jack" Hanna is famous for his decades of TV appearances, bringing wildlife to visit hosts including Johnny Carson, David Letterman, and Maury Povich. Hanna really knows his stuff, and putting animals on live TV is a recipe for unpredictable awesomeness. Here's a classic clip of Hanna in action in 1987, freaking out David Letterman with baby tigers, scorpions, and snakes:
When Stephen Colbert took over The Late Show, he needed a wild animal expert. Will Ferrell came by to give it a shot. The result is hilarious.
And of course, let's not forget Joan Embery with Carson: