Billy is a minor character in Going Commando. He is a humanoid-looking young child with two large antennae, who appeared in a Megacorp commercial for the Protopet, named "Why is Billy Sad?", filmed in Silver City on Boldan. In the commercial, Billy was depicted as alone and crying, with a narrator speculating why. When the Protopet arrived, Billy instead ran in terror, and at one point, called for the police, while the Protopet chased him and attacked him by biting and throwing him around. During this advert, the narrator ironically claimed the Protopet was merely playing with him.
Billy also appears briefly in the fourth episode of Behind the Hero, in which he was eating breakfast cereal while staring at a milk carton with an image of Qwark surrounded by "missing" question marks. Later, near the end of a news segment by Darla Gratch on planet Damosel, he was briefly seen behind her fleeing in terror from a Protopet, as the only non-robot in the scene.
At the end of Up Your Arsenal, Billy attended the premiere of the Secret Agent Clank film. He was seen with his own Protopet, who had since been rendered harmless through the use of the Helix-o-morph.