Full list, TMS appearances
#3 Joel Grey:
"Comedy Tonight"- sang line "Something appealing, something appalling, something for everyone a comedy tonight!" and is then clubbed unconscious by Beautiful Day monster.
"Sherlock Holmes sketch"- called Fielding the butler- accused of murder, eats the evidence- a glass, a photograph, the gun, Piggy (as the maid), and Baskerville the Hound (as Watson).
In the Joel Grey episode, Gorgon Heap has ears instead of horns (the look like cinnamon buns) and is performed throughout by Frank Oz.
#16 Avery Schreiber:
Wayne & Wanda, "Some Enchanted Evening"- he mishears "You may meet a stranger" as "You may EAT a stranger" and eats Wayne. I always wondered why he wouldn't eat Wanda as well- maybe she wasn't a stranger, though she and Wayne were so inseparable on the show that I doubt it. Plus she's one of the cultural, highbrow acts so it's unlikely she'd be seen consorting with monsters. On top of that she also seems pretty innocent and helpless, so if she knew Gorgon Heap it would've only been briefly (before she would wind up in his stomach).
Gorgon had horns and was performed by Richard Hunt.
#19 Vincent Price:
"Panel"- it is here that he gets his name, Gorgon Heap (I also originally thought it was Heath). He eats the gourmet chef, Pierre LaCousse (performed by Jerry Nelson) and then tries to eat Kermit.
Performed by Dave Goelz, I believe.
#25 Don Knotts:
Cold opening-
Scooter: "Don Knotts! Don Knotts! 25 seconds to curtain Mr. Knotts! What're you doing hiding here behind the table?"
Don Knotts: "Listen, nobody told me I had to share a dresing room!"
Scooter: "Oh, didn't they tell you about her?"
Don Knotts: "Her?!"
Gorgon Heap (wearing chorus girl headdress): "What'sa matter, sweetie? Ya don't like chorus girls?"
No horns, performed by Jerry Nelson.
#28 Rich Little:
"Inchworm sketch"- Lenny the Lizard eats the same worm twice, then tries to eat it a third time, but it is much longer. He pulls on it until he realized that it is not a worm, but the nose of a large monster, who eats him.
Horns and new nose, performed by Frank Oz.
"Rich is interviewed by the reporters"- brief appearance here, he has no horns or lines. He appears as one of a group of monsters at the end of this bit.
#66 Leslie Uggams:
"Hey There, Good Times"- opening number with Leslie and the Monsters. Gorgon Heap (no horns or lines) plays the drums.
Unless Gorgon appeared in the Bruce Forsyth episode (the only one I don't have) that list is complete.
Don't know if the character ever appeared in anything else besides TMS. Joggy might know that, try asking him.
David "Gorgon Heap" Ebersole