Other TMS episodes that Gorgon Heap could've appeared in

[Philip Kippel]

Sandy Duncan: in "A Nice Girl Like Me"
Dom DeLuise: in the animal shelter sketch
Rita Coolidge & Kris Kristofferson: in the cold opening and the closing number
Leo Sayer: in the cold opening
Leslie Uggams: in the goodnights, in addition to "Hey There, Good Times"

He also could've appeared in any "At the Dance" segment.

 

[TotallySpiesFan]

He also could've appeared in the audience.

 

[minor muppetz]

He could have been in the closing number in the Vincent Price and Julie Andrews episodes, he could have been anywhere in the Alice Cooper episode, he could have been one of the sherrif of nottinghams henchmen in the Lynn Redgrave episode, he could have been a pirate in the Glenda Jackson episode, and he could have been in the good nights in the Roger Moore episode.

 

[MartyMuppets]

When I thought about how he was used three times in season one of tms compared to Big Mean Carl on mt I thought to myself Carl had a starring role in the short lived muppet revival series whereas Gorgon was basically a bit part perennial extra.
As I said to a friend of mine once that gobbler who always introduces himself as Carl has enjoyed far more significant time on the show than his predecessor ever had,

 

[TotallySpiesFan]

More:

Florence Henderson: in "Happy Together"
Vincent Price: in the audience during Talk Spot
Ethel Merman: in the audience during Fozzie's Monologue
Zero Mostel: in the goodnights
Milton Berle: in "There Are Millions of Us Who Are Ugly"
Edgar Bergen: in "Consider Yourself"
Steve Martin: in the audience at the beginning of the show
Julie Andrews: in "I Whistle a Happy Tune"
Teresa Brewer: in "Cheese Cake"