Fraggle Rock: Live by the Rule of the Rock (1983)

Gobo has not received his usual postcard from his Uncle Traveling Matt. He eventually comes to realize that he must venture out into Outer Space to look for him. Meanwhile, Red and Wembley discover a creature who is whatever you believe it is. The trouble starts when Ma Gorg believes it into being a monster in the basement of the castle. And Cotterpin Doozer decides she’d rather be a Fraggle like Red, than spend the rest of her life building with the Doozers.