In 1968, Parkes won the first Canadian film award (then called the Etrog and now known as the Gemini) for his portrayal of Uncle Matthew in the movie Isabel.

When he was cast in Fraggle Rock, Parkes was finishing a regular role as another type of "doc," playing Dr. Arthur Lowe (no relation to the English actor of the same name) on the Canadian TV series Home Fires.

After Fraggle Rock, in addition to returning as Doc in A Muppet Family Christmas, he continued to work in children's television, guest starring as alcoholic photographer Phil (opposite Sesame Park puppeteer Nina Keogh) on the TVOntario puppet series Today's Special, and appearing regularly on PBS's Shining Time Station as store owner Barton Winslow.

In 1995 he also portrayed the priest at St Bart's in New York in the Olsen Twins movie It Takes Two.

He appeared with Willem Dafoe and Billy Connolly in The Boondock Saints (playing a Tourette's syndrome-afflicted bartender, also named "Doc").