Billy is a rubber band owned by Charlie. Charlie found him and named him, so now he is his. Charlie loves Billy a lot, and he even dove into the toilet to save him after Junior Small threw him in. He is consitered a character of Another Oobi Vacation even though he is only a rubber band.
Billy is a yellow rubber band (SillyBand) in the shape of a bee. According to Bluedog who actually owns him, Billy is glow-in-the-dark.
Billy only makes a small appearence in Small Problem.