Wally debuts in Chapter 185.
Before his debut, Wally secretly procures a PokéNav, intending to use it on his Pokémon Journey.
Wally is about to move to Verdanturf Town but before he goes, he asks Petalburg's new gym leader to teach him to catch a Pokémon. He wants to retain something from his life in Petalburg City. The man agrees, and Wally goes into the forest to try on his own while he waits for him.
Ruby then finds him ailing behind some bushes. Wally praises Ruby's Mudkip's skills and Ruby is immediately enthusiastic, offering to help him capture a Pokémon. Wally declines, telling Ruby that he's being taught by somebody else.
Ruby suddenly pulls Wally behind some bushes just as Norman arrives, looking for Wally. Wally is shocked when he finds out that Ruby is Norman's son. Their attempt at hiding fails and Norman calls Wally out of hiding. Wally comes out gladly but doesn't reveal Ruby's presence. Norman reprimands Wally for not informing him of his illness and impending move from Petalburg, telling Wally that he won't teach him to catch a Pokémon. While Norman is distracted, looking for some other presence (Ruby), Wally either has an episode or is affected by Norman's Slaking's Swagger.
Ruby takes Wally to his house, where Wally's parents thank him and invite him to stay the night. Wally awakes and realizes his parents must have asked Norman to not teach him, and upon hearing his, Ruby is filled by indignation on Wally's behalf, offering to lend him a Ralts, "Ruru" for the night so that the two of them could go out into the wild as a show of rebellion and to catch Wally a Pokémon.
The two go out to Petalburg's outskirts, where Wally uses Ruru to battle a Kecleon. Wally captures the Kecleon, the very first Pokémon he's ever caught. He doesn't have long to celebrate, however, because suddenly an earthquake—which had become more common recently—hits, separating Wally and Ruru from Ruby. However, Ruru communicates to Wally that Ruby is still alive: he can still sense him.Verdanturf Town, where in the hospital he met an old man who offers to bring him to a better place for recovery: Pacifidlog Town. Wally accepts and goes with him, and along the way he captures a Roselia and Cacturne.
When Kyogre awakens, the storms and turbulent waves make Pacifidlog unsafe to inhabit. However, Wally's friend—the old man he met in Verdanturf—wants to remain in Pacifidlog so that he can stay on the lookout for a mysterious island. Wally convinces him to only stay one more day, and if the island isn't visible, then they'll leave.
The next day, the island isn't visible, and Wally goes to pick the man up. He arrives in time to save the man when a violent wave rocks the building and causes the man to fall out the window. Wally has his Kecleon save him. The two then go on rafts to seek out safety.
On the ocean, Wally spots a bag with a pokéball and pokédex in it, about to be lost to a wave. Wally has his Cacturne use Needle Arm to pin the bag to a rock, risking having a needle hit and shatter the pokéball. Wally retrieves the bag and his Roselia uses Aromatherapy and Grasswhistle to heal and put the Pokémon, Treecko, to sleep.
A voice suddenly admits to being impressed and asks Wally why he used Needle Arm, endangering Treecko, and Wally says it was because he trusts his Pokémon.
Norman gives Wally a test: to reach the last floor of Sky Pillar. He gives Wally special rotating sleeve cuffs to store his pokéballs in and leaves a Mach Bike for Wally to use. Wally falls through the floor but Treecko saves him and points out the bike. Wally works his way up the floors and has trouble breathing, so he pulls on his oxygen mask.
He reaches the 49th floor and is attacked by a Dusclops, who creates a black hole. Wally puts his trust in Treecko and sends him out to use Leaf Blade on the black hole. Treecko evolves as he executes the attack, and Wally successfully reaches the 50th—the final—floor.
Norman appears and tells Wally to remove his oxygen mask. Wally does so and is surprised to discover that he can breathe more deeply; Norman informs him that training so hard at these high altitudes has made his lungs stronger. Wally, becoming teary-eyed, admits that Dusclops was the first wild Pokémon he had defeated.
Wally continues to train with Norman and becomes a strong trainer in his own right. Both Ruby's Ralts and Professor Birch's Treecko evolve while training with Wally, something that Wally is guilty about because they are not his so he shouldn't have let them evolve.
When the crisis in Hoenn comes to a head, Norman tells Wally that they are going to awaken Rayquaza , who sleeps at the top of Sky Pillar. The top floor can only be reached through small passageways, small enough that only a child can get through. Wally realizes that Norman initially intended to awaken Rayquaza with his son, Ruby, but now is using Wally as a substitute. Deciding that he is alright with that, Wally goes through with it and awakens Rayquaza using the two Pokémon who don't belong to him: Kirlia and Grovyle. After awakening Rayquaza, Wally passes out, but not before he sees Norman leave with Rayquaza for Sootopolis City.
Wally is slightly small for his age and appears to be quite skinny. He has hazel coloured hair that spikes in places and baby-blue coloured eyes, and wears a long sleeved white button up shirt, tan coloured trousers and baby-blue and white coloured slip-on shoes. Later on, Wally wears a dark green coloured respiratory suit, which is designed to help him breathe.
Wally is a kind, calm and usually quiet character. He is a caring boy who always puts others before himself, and he seems to be determined to do what he wants, despite his poor health.
- Needle Arm
Cacturne uses Needle Arm to save Treecko. He has very good aim.
Wally finds Treecko adrift in the sea and saves him.
Ruby lent Wally his Ralts to help Wally capture his first Pokémon, a Kecleon. However, when the two were separated Wally took care of Ralts until he had a chance to return him to Ruby. It can be assumed that they are still good friends.
- Judging by his symptoms (problems breathing, coughing and wheezing, tiring easily, fainting), Wally's medical condition may be asthma.