Stephenson passed away on 15 May (15) at an assisted-living facility in Woodland Hills, California after a three-year battle with Alzheimer's disease, his son Roger confirmed.

He is best known for voicing 1960s U.S. TV cartoon characters including Mr. Slate on The Flintstones, Fancy-Fancy on Top Cat, and Blubber Bear on Wacky Races.

He also worked on TV shows Jonny Quest, Fantastic Four, The Transformers, Bionic Six and a number of incarnations of Scooby Doo, as well as narrating cop drama Dragnet, which aired between 1967 and 1969.

Stephenson also enjoyed minor roles in TV shows including The Beverly Hillbillies, I Love Lucy, The Man From U.N.C.L.E. and Mission: Impossible.