Muppets come in every shape, color, and size, but the biggest stars are the basic characters: the frog, the pig, and the dog. Originally created by Jim Henson and Don Sahlin for a Purina Dog Chow commercial, Rowlf quickly became an in-demand dog. Rowlf was a perfect sidekick for Jimmy on the popular Jimmy Dean Show, making him the first Muppet to have a regular gig on a network TV show. In 1976, Rowlf made a career change -- he joined the cast of The Muppet Show as the in-house pianist. Rowlf favored Beethoven and standards, but he was so amiable and friendly, we're guessing he was okay with taking requests, too.