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The Treasure of Fraggle Rock is a song. Fraggles once believed this lost treasure was a bunch of diamonds, speculating that it may be a million or even five million diamonds (each one making a nice skipping stone). The treasure turned out to be a music box, with a song that all the Fraggles could share.
There was a map to the treasure, which was drawn by a Fraggle named Dwight at the "time of the Third Drafting," about a "zillion squintillion days ago," according to Gobo Fraggle. The map leads into the Gorgs' Castle where the treasure was hidden above the Gorg family's fireplace.
The Treasure of Fraggle Rock has also been referred to as "the Ancient Treasure of the Fraggles" and "the Lost Wealth of the Fraggles."