The greaseberry plant
Greaseberry plants grow in the Gorgs' Garden. The leaves of the greaseberry plant are harvested (when in season) by the Fraggles and used for sliding across the Great Hall. Some Fraggles have attempted what is known as "The Ultimate Slide". The leaves are also used to play the sport of rock hockey.
Boober Fraggle keeps a supply of greaseberries for his recipes, and in one episode, Boober uses the greaseberries in his radish gumbo when he is unable to retrieve any radishes for it.
The seeds of a greaseberry make soup taste awful to the Gorgs. Pa is the only Gorg to enjoy such soup's flavor. This information was put to good use in one episode when Marjory was frozen over. In order to thaw her out, Gobo and Mokey added greaseberry seeds to the Gorgs' goombah soup. This made the soup inedible, according to Ma, and it was thrown into the Trash Heap.
The plant is used to make Gorg butter, and greaseberries can also be pickled, a dish which gives Pa Gorg headaches, as in Sprocket's Big Adventure.