Jim Henson and Jerry Juhl originally developed this as a TV special in 1968 titled "The Musical Monsters of Turkey Hollow", but it remained unproduced. A comic book adaptation (which follows the original outline more closely) was published by Archaia in 2014.
Jim Henson wanted to film the story in the natural world rather than a studio, and took various pictures of the five prototype Monster puppets behind his Connecticut farmhouse. His young daughters Lisa and Cheryl held the puppets in place for this photo-shoot. Lisa Henson eventually executive produced the 2015 TV version.
The photos of Aunt Cly's late husband, Uncle Ned are of the film's director, Kirk Thatcher.
Had the original version been produced in the late sixties/early seventies, it would have featured songs written by long time Henson associate Joe Raposo, with the musical sounds that the monsters made were to have been created on an electronic synthesizer by Raymond Scott.
Muppet builder Don Sahlin turned Jim Henson's sketches for the musical monsters into five puppets and for the first time incorporated a variety of lifelike taxidermy eyes as well as fur based on a mossy palette. These prototypes served as the inspiration for the look of the monsters in the 2015 version.