While he had a long career in TV and film including a memorable part in the Boondock Saints films, he will always be remembered by Muppet fans as Fraggle Rock's Doc.
After Fraggle Rock, Parkes reprized the role in 1987's A Muppet Family Christmas in which he tried to rent Ma Bear's farmhouse for a "nice quite Christmas in the country." (Skip to 2:25 in the video below to see him meeting Ma Bear and the rest of Muppet Show Muppets)
Head over to ToughPigs to read their great tribute and remember: "The turkey's not the turkey, the turkey's the turkey, you turkey", and more appropriately "You cannot leave the magic."
As Kermit once said, " What a sweet guy." You'll be missed, Doc!