He gained notoriety throughout the late 1980s and 1990s as an animator for Jetsons: The Movie, Once Upon a Forest, The Town Santa Forgot and The Ren & Stimpy Show, among others.

Baboon, two characters featured in intermediate segments of Cow and Chicken, premiered on June 10, 1999, as a standalone series and ran for one season.

Since Cow and Chicken and I Am Weasel, Feiss has continued to work in the animation industry on projects such as The Grim Adventures of Billy & Mandy, Dave the Barbarian, Open Season, Despicable Me 2, The Grinch, The Willoughbys, Hotel Transylvania: Transformania, and Minions: The Rise of Gru.

[4][5][6] He worked on the 1980s revival of The Jetsons, where he was acquainted with John Kricfalusi; the duo became friends, and Feiss helped animate "Big House Blues" as a favor.

In issues #5 and #30 of his cousin Sam Kieth's comic book The Maxx, David showcased his work with The Crappon (which looks like the Warner Bros. frog mascot Michigan J. Frog), Fred Flower and Uncle Italian Moose, which had a very similar style to Cow and Chicken (they are reprinted in WildStorm's The Maxx Volumes 1 and 5 trades).