[4] His film acting work includes Jack in the original Invasion of the Body Snatchers (a role later reprised by Jeff Goldblum in the 1978 version), Solly in The Defiant Ones, Joe Capper in Cowboy, Mack McGee in the original Angels in the Outfield, Major Collins in The Perfect Furlough, and an uncredited but recognizable role in Singin' in the Rain as Rod (head of the Publicity Department).

[5] In 1968, he toured with his wife Imogene Coca in a productions of You Know I Can't Hear You When the Water's Running and Once upon a Mattress.

Notable television roles include Jake Clampett (a deadbeat who mooches off the Clampetts) for two episodes of CBS's The Beverly Hillbillies, Blanche Morton's (Bea Benaderet's) brother Roger Baker on eight episodes of The George Burns and Gracie Allen Show, and Harvey Helm in a 17-episode stint on NBC's The Bob Cummings Show.

In 1956 he appeared as Joe Baker on the TV western Cheyenne in the episode titled "Mustang Trail."

He portrayed Marty in "Academy Award," a 1957 episode of the CBS situation comedy Mr. Adams and Eve.

Donovan guest starred as Paddy Britt in the 1959 episode "The Boy from Pittsburgh" of the NBC western series, Riverboat.

Between 1965 and 1967, Donovan had a recurring role as neighbor Herb, whose mission in life seemed to be getting from his house through the study window of professor Jim Nash in less than a full minute, on the situation comedy Please Don't Eat the Daisies.