Junior watches the tree's last leaf.
The Nirvana Tree is a species of tree found in the Gorgs' garden. According to Gorg tradition, the Nirvana Tree marks the beginning and the end of a King's reign. Once all the leaves fall off, another Gorg becomes King.
Its magical effects were shown in the episode "The Gorg Who Would Be King." By eating one of the leaves Junior was shrunk to the size of a Fraggle for about an hour.