Ro-Bear Bill is a member of the Berbil race (also known as Ro-Bear Berbils), a group of small robotic bears.
He made fast friends with the Thundercats. Once Panthro repaired him after he'd been attacked by the Conquedor. The pair worked together to build weapons to fight the Conquedor. He and the Berbils are now trusted allies of the ThunderCats.
Ro-Bear Bill has the ability to form a small sphere and roll and bounce at a relatively high speed, and he is a skilled mechanical engineer, comparable to Panthro.