TenNapel began as an animator on Attack of the Killer Tomatoes: The Animated Series.^{[citation needed]} He soon began working in the video game industry on projects like 1993's Jurassic Park and Stimpy's Invention for the Sega Genesis and The Jungle Book for the SNES and Sega Genesis.^{[citation needed]} In 1994, he created Earthworm Jim, the character that would star in Shiny Entertainment's video game, toy line, and cartoon series. In 1996, working for DreamWorks, he created for The Neverhood for the PC. The sequel, entitled Skullmonkeys, followed in 1998.^{[citation needed]}
On television, TenNapel was the creator of the Project G.e.e.K.e.R. cartoon series for CBS. He was also a consulting producer on the ABC series Push, Nevada with Ben Affleck.^{[citation needed]} Towards the end of the 2000s, he also created two shorts for Frederator Studios and Nicktoons, "Solomon Fix" (computer generated 3D) and "Squirly Town" (traditional 2D).^[2]