Buster is Andy's pet dog who became his Christmas present in the first film. He first appears in Toy Story 2.
His barking sounds were provided by an uncredited Frank Welker.
Andy's first gift on Christmas at the end of the film is a present, which is believed to be Buster. Buster is never seen, but his barking is heard at the very end of the movie.
Toy Story 2
In Toy Story 2, Buster makes his first full appearance as a brown miniature dachshund. He is able to understand the toys when they talk to him and is shown to be friends with Woody.
He is first shown as he bursts into Andy's room to find Woody having to be held off by Rocky Gibraltar and the Green Army Men, and after he takes Woody out of Andy's backpack, he pins Woody to the ground and growls at him, but quickly begins to lick him repeatedly after sensing that Woody is actually alive. It turns out that Buster and Woody were playing hide-and-seek.
Woody then asks Hamm how Buster did, and it is revealed that Buster set a new record of 13.5 seconds, as shown on Mr. Spell. A little later, when Andy's mother takes Wheezy with a broken squeaker out to be sold at a yard sale, Woody, thinking quickly, whistles for Buster (though Woody had to use his other arm due to his good arm having been inadvertently broken by Andy earlier), and he takes him out to the yard sale (though Buster, when told to be "subtle," does it in an exaggerated manner before Woody pointed out he didn't mean that level of subtlety), where Woody climbs into a box to dig out Wheezy and bring him back to Andy's room. Unfortunately for Woody, Buster jumps over a toy while heading back to Andy's room, causing Woody to fall – which leads to the events of the movie. Buster is barking at Al McWhiggin who is trying to steal Woody and Mrs. Davis tells him to keep it down.
At the end of the film, Buster is shown alongside Slinky, who understands that Buster wants to get out of the room, and Jessie performs a stunt with a Hot Wheels car and track to reach the doorknob to let Buster out. He is last seen when Woody sees Andy, Molly, and their mother go out for another family outing.
Toy Story 3
In Toy Story 3, Buster, now 10 years older, makes his final appearance. He is now very old, mixed brown and a little gray, has a gray-white snout, is fat, and is unable to help Woody and his friends, even though he continues to remain friends with them.
After seeing his friends getting thrown away by Andy's slightly aged mother, Woody, thinking quickly, whistles for Buster for help getting downstairs to rescue his friends from getting thrown away. However, after Woody hops onto Buster's back so he can run outside to save his friends, the elderly dachshund instead yawns and falls fast asleep on Woody. Then, Woody turns Buster around for air.
Buster is last seen being with a 17-year-old Andy when he departs for college, telling his pet dog to keep Molly away from his stuff.