Muppet Monster Adventure was adapted from an unproduced script for a Muppets movie titled The Muppets' Haunted House.
Also Appears On: Muppet Monster Adventure (Game)
https://thenerdlys.com/2018/08/13/episode-134-kirk-r-thatcher/ - Timestamp 0:47:19
In 2013, around the launch of Disney Infinity, Disney merchandise artist Jim Valeri posted a set of images to his portfolio of angular figures, resembling the character models from Disney Infinity, of Muppets Kermit, Gonzo, Miss Piggy, Animal, Beaker, and Fozzie Bear, mentioning that they were made a year ago and he had no clue what they were for or if they would be released. While not explicitly stated, it seems heavily likely from the timing and aesthetic that these were intended as characters for Disney Infinity who never saw the light of day, possibly due to the financial failure of the 2014 film Muppets Most Wanted.
Also Appears On: Disney Infinity (Game)