Performer(s) Appeared in Jerome Crystal, better known as Doc, is a character from the Jim Henson television series Fraggle Rock. He is an inventor who lives with his dog, Sprocket. He spends a lot of time in his workship which, unbeknownst to him, has a hole that leads into Fraggle Rock. In each episode, he finds himself receiving Uncle Traveling Matt's postcards to Gobo Fraggle and being puzzled as to how he keeps getting them, which he always then throws into his wastebasket (after which Gobo retrieves them with Doc not even noticing). He remains unaware of the Fraggles' existence up until the show's second-to-last episode, "The Honk of Honks", when he actually meets and befriends Gobo.