Not to be confused with Billy No-Friends or Billy Gulch.
Billy is one of the Emerald Hill folk. Along with thirty-four others, the dog was captured by Doctor Ivo Robotnik's forces and sent to a Badnik Processing Plant on the outskirts of the Metropolis Zone. Whilst he was waiting in line to be converted, Billy lost his cool, not wanting to wait for his turn to become a Badnik. Billy fled from the line and attempted to escape the facility, despite pleas from his fellow prisoners. The lizard caught him with his whip before he could reach the stairs. Billy was about to be brutally punished when the intruder alarm sounded, announcing the arrival of the Freedom Fighters.
Soon afterwards, Billy was transported to the Floating Island through a Star Post and remained in the Mushroom Hill Zone until Robotnik was finally defeated.