Volleybubble is a two-player game (it can also be played by one player) played in the episode Fishketball!. The game is played with a bubble.
Two-player mode
Player 1 says "One..." and blows the bubble to Player 2, who says "Two..." and blows it back. "Player 1 says "Three..." and blows it to the middle. Both players say "Pop!" as the bubble pops.
One-player-mode
The player says "One...", shifts to the other side, says "Two...", blows it back, shifts sides again, says "Three...", blows it to the middle, and says "Pop!" as the bubble pops.