Harnell's voice roles for Hanna-Barbera, Cartoon Network and Warner Bros. include
- A flute player, a constable and Shane Flinty on What's New, Scooby-Doo?
- A guard and the human form of Scooby-Doo in Big Top Scooby-Doo
- Secret Squirrel and several supporting characters in the Super Secret Secret Squirrel segment of 2 Stupid Dogs
- Droop-a-Long Coyote and Hardy Har Har on Wake, Rattle & Roll
Harnell states in "Animaniacs Live" in the special features of Volume 1 of the DVDs that for Wakko Warner he did a John Lennon voice, then when he saw the picture of Wakko and how small the character was, he changed the voice by making it higher pitched, like a small John Lennon.
- Jess Harnell at the Internet Movie Database