Off the top of my head:
Phil Hartman
Linda McCartney
Stephen Jay Gould
George Harrison
Doris Grau (Lunch Lady Doris)
Am I missing anyone?
Heh. Not only did I read that thread I contributed to it.
Us old-timers will do that. I’m afraid to do searches sometimes, because I’m sure one day I’ll see that I started multiple threads asking the same question.
Chris Latta, who apparently was the first voice of Mr. Burns and Moe, is dead.
Ron Taylor, who voiced Bleeding Gums Murphy.
Audrey Meadows, who was Grandpa Simpson’s girlfriend Beatrice Simmons.
Chick Hearn.
Steve Allen (Audrey Meadows’s brother-in-law, among other achievements).
Bob Hope.
Barry White.
George Fenneman.
Tito Puente, Latin jazzman.
Jack Lemmon.
Franklin Delano Roosevelt, our 32nd President (heard in archive footage).
Joe C., a 3’ 9" dwarf who performed with Kid Rock.
John Entwistle of the Who.
Isabel Sanford.
On the In the Actor’s Studio episode that the Simpsons cast was on, Hank Azaria tells the story of inventing Moe’s voice.
“Can you make that voice there more gravelly, Hank?”
Out comes the voice of Moe.