He’s basically just a baby who has freckles, no hair, and is wearing nothing but a diaper.
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. Chewing and dribbling on his teething ring and destroying his beads. 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 attempts to rush out of the room but instead ran directly into his box, quickly realizing and using it to gain momentum before running beneath the couch. While walking and trying to find Tinny, Billy falls over, and begins to cry. Pitying the infant as no one came to console him, 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 recovers he becomes furious to see the infant playing with a box. Tinny tickles his foot to get his attention but Billy moves over, only for the camera to reveal the infant now stuck in the paper bag shown at the start of the short that Tinny came in, 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 around and out of the room with Tinny selfishly in chase not realizing the potential danger the infant is in.
- In the credits of Tin Toy, Billy is credited as playing himself. Which is a nod to the plot as Billy repeatedly does things that lead to misfortunes (tormenting Tinny, throwing Tinny across the room) and is then punished (falling face first, playing with a paper bag only to end up not being able to play with anything at all)
- 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. There is even audible flatulence when he falls onto the floor but the sound is lessened by the impact noise.). 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.
- His age is a point of contention as from what we see in the short all the toys belong to Billy but it's questionable why an infant would own a Tin Toy that is made of metal or own toys that are as tall as him. To add onto this, the only word he ever speaks is "poopy" right before he exits the room with the paper bag over his head with Tinny in chase. Thus truly painting a grim reality for the infant.
- His ultimate fate is presumed unknown as he is never referenced in any other Pixar media yet his toys make several appearances throughout the Toy Story saga.
- As the credits roll right before they walk out of the room, Billy utters the word "poopy" before whining on the way out of the room. This was the only word spoken by him in the film.