The Mangosteen is the prize to join TPOT 1. Two thought it was a purple tomato. When the debut ends, Winner ends up winning and eating it.
Tetherball is a game played by Grassy and Tree in the TPOT intro. Tennis Ball also stated that he and Remote use to play it in BFB 7.
Grassy and Tree playing Tetherball in the TPOT intro.
The tetherball whacks Tree in the head/face.