Jim Henson spent many hours at the Robotorium, INC with Debbie the Roboteer learning to use the new Apple IIE desktop computer (her cousin programmed with the first RS232 interface ports) and interfaced with a Rhino XRII bored out airplane aluminum 6 to 8 axis robotic arm. Through experimentation they came up with a way to have one puppeteer use an actuated mitt controller arm to animate miniature puppets (the worm-like critters) or even choruses of different puppets through the use of the same robotic applications and programming. The mitt ran the motors on each axis of each of the puppets. The puppeteer put their arm into the mitt controller and went through the motions.
Karen Prell, the voice of Red Fraggle, auditioned for and very much wanted the role of Mokey. Jim Henson called her up and decided to hire her, but for the role of Red. Prell was excited to be hired, but when she hung up the phone she thought to herself, "They want me to play RED?"
When Jim Henson first thought of the show, the working title was "The Woozle Show."
Originally, five different endings for the opening, with each of the main Fraggles saying "down at fraggle rock", were filmed and meant to alternate between episodes. However, the one with Boober was the only one consistently used. One with Wembly was included in the episode "The Terrible Tunnel", while one with Gobo was used in "The Finger of Light".
The Gorgs required two performers each: an actor to perform in the costume, and a puppeteer to do the voice and operate the face by radio controls. Previously, full-body Muppet characters (e.g., Big Bird) required the performer to operate the head with one hand, leaving the character with only one functional arm. Operating the face from outside allowed for a more expressive performance from the characters. Furthermore, video cameras installed inside the eyes allowed the performer to see from the Gorg's point of view.
The names "Gobo" and "Traveling Mat" are film-industry in-jokes, both being words describing techniques to super-impose images over a different background.
When HBO first started it was purely a movie channel. (HBO = Home Box Office) This was the channel's first original series.