8-Ball is a pool ball-the black 8 to be exact. Unlike the other balls, he moves around by rolling. His limbs, they are nonexistent.
8-Ball will not let people forget that he doesn't have a favorite number. Despite his uninterested tone of voice, he once inspired his team to overthrow Golf Ball as its leader, telling everyone to do the opposite of what Golf Ball said.
However, it was revealed that everything 8-Ball said was meant sarcastically, and he was only trying to boost spirit of the team.