As Atari may be seen to rebellious and has amnesia, he is actually kind-hearted and knows between right and wrong. He is also intelligent and is always there to help others in need.
Appearance in the film
Atari begins his journey on plane to find Spots on Trash Island. The plane crashes, but Atari is rescued by Chief, Rex, King, Duke, and Boss. All the dogs, but Chief agree to help Atari find Spots. Atari and the dogs begin their search for Spots. They find a bolt-locked cage with the dead bones of another dog, named Sport. Assuming that its Spots, Atari tearfully mourns over the corpse and hosts a funeral. The dogs help rebuild Atari's plane as he prepares to return home, with Chief refusing to help. Atari starts his planes but stops after realizing the wrong dog had died. Atari decides to stay at Trash Island for longer until he rescues Spots. Atari and the dogs stay at a glass bottle hideout where he tells them that Kobayashi is responsible for bringing Spots and the other dogs from Megasaki to the Trash Island. He tries to interact with Chief, but Chief refuses to let Atari do so. However Chief changes his mind to accompany on Atari's search for Spots. The next day, Atari and the dogs journey across the island. The pack takes a stop at an abandoned athlete and tell their backstories before the Trash Island event. They later stop at a rusty boat where they meet Jupiter and Oracle with some nifty directions. They had to continue venturing through the east of Trash Island, cross the Middle Fingers, and make their way to a forgotten private-lab where Spots is staying. The next day, Atari and the dogs leave the ship and ride a trash converter. However, the ride splits into two separating him and Chief from Duke, Boss, King, and Rex. Atari has no choice but to accompany with Chief. After playing some fetch at an abandoned theme park, the two become friends, while Chief starts to think that maybe befriending a human isn't so bad after all. Chief allows Atari to bathe and groom his dirty fur. Shocked, Atari notices that Chief and Spots are identical except with different noses.
A year before the film, Atari was one of many victims in a train crash. He survived, but his parents couldn't. Atari is sent to a hospital and is diagnosed with memory loss. During his stay he receives a dog communicator and meets his new bodyguard named Spots whom he befriends. After his hospital stay, Atari and Spots live with Mayor Kobayashi in the Brick Mansion. 6 months later, Atari had no choice but to give up Spots to Trash Island. Another 6 months pass, and Atari begins his journey to find his dog. He creates an audio message for Mayor Kobayashi to ignore.