Invisibility Soup is the chanced upon discovery by Boober in Episode 219: Doomsday Soup. When Boober runs out of radishes for his famous Radish Gumbo he's forced to improvise and substitutes skunk cabbage, greaseberries and rutabagas instead, which the Fraggles are not very fond of. The soup is terrible and with his reputation as a Fraggle chef on the line he pours it into his laundry wash water contaminated by rock soap with yeast added to it (as a practical joke). The mixture creates a "soup" turning anything it touches invisible for a short period of time. The Fraggles see it as an easy means to plunder the Gorgs' garden any time they wish for radishes. Boober also might get to make radish gumbo after all. Within a short time though the soup mixture becomes unstable causing rockquakes and ultimately explosions. Boober decides it must be disposed of. Junior Gorg interupts the disposal and ends up blowing up all of Ma Gorg's Spring cleaning clutter.