In terms of appearance and personality, Billy is a pretty typical baby. However, he is heavily implied to suffer from neglect at a young age. He always plays with toys by himself and abuses them, vengefully in some cases as noted when he grabs and tosses Tinny. Even when he trips and starts crying, his parents don't do anything about it and ignore the wailing.
Role in the short
In the short, he is delighted to play with Tinny, who is initially happy to play with Billy until he sees how roughly the infant handles his other toys. When he tries to walk away, his musical instruments on his back play notes, intriguing Billy, who playfully crawls in chase before getting up to walk. Tinny soon finds cover under the couch. While walking and trying to find Tinny, Billy falls over, soils his diaper (noted by the yellow accenting on the diaper from this point on towards the lower half), lies on the floor, and begins to cry. Pitying the infant and seeing no intervention from his parents, or the other toys beneath the couch Tinny tries to go and cheer him up. When he does, Billy manages to cheer up, but not before grabbing and shaking Tinny violently and throwing him to the side, showing how ungrateful the infant is. He then begins to play with the cardboard tin toy box and when Tinny attempts to reconnect with the baby he just ignores him and continues play with the box and paper bag Tinny came in, eventually placing the bag over his head before getting up and waddling aimlessly around the room. Tinny tries to follow Billy to get his attention, but is still ignored as Billy waddles away. As they walk aimlessly out of the room Billy becomes more aware of the situation he is in and begins crying as they exit the room in a sharp contrast to the joy presented by the toddler in the beginning. After Tinny and Billy leave the other toys come out from under the couch and begin playing.
- In the credits of Tin Toy, Billy is credited as playing himself.
- In Toy Story 2, when Hamm is rapidly turning the channel, Billy is briefly shown between channels.
- Throughout the short, Billy's diaper progressively becomes more and more yellow, implying the infant soiling himself in either excitement (when he dribbles on himself after biting the teething ring, though this could also be yellowing as a result of Billy discarding the spit in his diaper) or sadness (after he falls and cheers up the bottom half of the rear of his diaper is a bright yellow for the rest of the short film). This is most evident at the beginning of the short when he crawls into the room as his diaper is normal shades of white and blue vs when he waddles away at the end where the front and bottom half of the rear of his diaper are yellow.