The Baby Volleyball is a pearl that only appears in the episode "Porous Pockets."
The pearl is light purple and is very shiny and round. In comparison to the characters, it is quite large. It is extremely valuable.
Role in episode
SpongeBob thought it was a baby, but Patrick thought it was a volleyball, so SpongeBob came up with the name of "Baby Volleyball." They started playing volleyball with it, until the Appraisal worker told them it was of great worth. They sold it to him, and SpongeBob became rich.