In television, Morris is most famous for his work on Your Show of Shows (which also starred Imogene Coca), as well as portraying Ernest T. Bass in The Andy Griffith Show.
In movies, Morris appeared in Mel Brooks' High Anxiety, The History of the World, Part I, and Life Stinks. He was also in Boys' Night Out, The Nutty Professor, Splash, and The Wonderful Ice Cream Suit.
Morris' early voiceover appearances included Beetle Bailey and His Friends, the Gene Deitch film Munro, The Flinstones, The Jetsons, Magilla Gorilla, Peter Potomus, Breezly and Sneezly, Atom Ant (with Don Messick eventually taking over), Disney's Winnie the Pooh, The Archie Show, and Groovie Goolies. He later voiced characters in Paw Paws, The 13 Ghosts of Scooby-Doo, Galaxy High, Police Academy: The Series, and Cow and Chicken.
Morris also directed movies and television shows, including The Andy Griffith Show, The Dick Van Dyke Show, Bewitched, Hogan's Heroes, With Six You Get Eggroll, Don't Drink the Water, Who's Minding the Mint?, One Day at a Time, Goin' Coconuts, The Love Boat, and Trapper John, M.D. He voice directed animated series such as Kidd Video, The Mighty Orbots, Galaxy High School, Bionic Six, and Police Academy: The Series.
In a series of commercials for Qantas Airways, Morris provided the voice of the koala ("I hate Qantas"). He was also the first to voice the Hamburglar in McDonald's commercials.
- Roscoe (Country Cousin)
- Movie Actor (The Carnival Curse)
- Mr. Wishnitsky
- Party Dogs (The Fairy Dogmother)
- Sheriff (Dogmother 2)
- Bailiff (Dogmother 2)
- Wade Duck
- Bug (I Like Having You Around!)
- Wade's Ancestor
- Haimie (Over the Rainbow)
- Billy Buddy Bear (2nd time)
- Jack's Mother (Jack II - The Rest of the Story)
- Dr. Karloffis Boar
- Edna W. Outraged (Fine Feathered Funny Man)
- Customer (Grape Expectations Part 1)
- Aerobics Instructor
- Doctor (Newsworthy Wade)
- Igor (The Monster Who Couldn't Scare Anybody)
- Wade namechecks The Andy Griffith Show in "Sooner or Later".