Max (Japanese: マサト Masato) is a young boy from the anime and a former traveling companion of Ash. He is not a Pokémon Trainer and he did not own any Pokémon during the entire Advanced Generation series. He is the younger brother of May and the son of Norman—the Petalburg Gym Leader—and Caroline.
In his debut episode, Max was presented somewhat of a know-it-all who was proud of his book smarts. For example, in In the Knicker of Time! Max did not approve of how Ash had used Pikachu in battle and spent a portion of the episode lecturing him on what he thought was a better way to command the Pokémon. But despite this attitude, Max was not a close-minded person and was always eager to learn about Pokémon first-hand. He would become particularly excited when he could experience a Pokémon's attack or Ability, such as Jigglypuff's Sing or Sharpedo's Rough Skin. Max went under Brock's tutelage for real-world knowledge of Pokémon and how to care for them. Max developed a friendly relationship with Brock, though he did adopt Misty's habit for yanking Brock by the ear whenever Brock saw a pretty woman.
Despite getting off to a rocky start with Ash, Max truly admires him and has been proven it on numerous occasions. Over time, Max saw how Ash's unorthodox battle strategies could be beneficial, and by the end of the Advanced Generation series Max was no longer criticizing Ash's battling style.
He shares a deep bond with his older sister May, and their bond only grew stronger while they travelled together through Hoenn with Ash and Brock. However, the siblings were occasionally aggressive towards each other, like when Max told Harley embarrassing stories about May. Another example occurred in the movie Jirachi: Wish Maker, when May asked Jirachi to "get rid of the problem," referring to the large pile of candy in the room. Jirachi, who was reading Max's thoughts, teleported May away, which suggests that Max had been thinking that May was the real problem. Despite their arguments, the two siblings care for each other very much.
The question of Max's starter Pokémon was raised a number of times while he was traveling in Hoenn. Between the Hoenn starters, he said that he would have chosen a Treecko. However, in Having a Wailord of a Time he commented that he could really receive anything. Not knowing who his starter would be lead to some of the conflict with his doppelgänger, whose name was also Max, in Maxxed Out!. At the end of that episode, he stated that Max is lucky that he already knows the Pokémon he will start his training with. Max finally did meet his future partner in Do I Hear a Ralts? when he befriended a weakened Ralts. Wanting to demonstrate that he could be responsible for a Pokémon, he took care of it and brought it to a Pokémon Center with a little help from Snorunt. When Max and Ralts parted ways at the end of the episode, they promised to meet up again when Max was eligible to be a Trainer.
Max first appeared in There's no Place Like Hoenn where he was inside the Petalburg Gym when May returned home with Ash. When he saw Ash, he claimed that he was the Gym Leader. He questioned Ash about the Silver Conference, saying that he had watched the Silver Conference live when Ash was a participant and was not impressed with his performance. As the two began to bicker over how Ash could have won his Silver Conference battle against Harrison, May arrived with her parents and revealed that Norman was the actual Gym Leader instead of Ash. Max watched the match between Norman and Ash until it was interrupted by Team Rocket. He goes after Team Rocket and falls for their pit traps when he found Torchic. Later, he decided to join Ash and May when they were setting off to Petalburg Woods.
In In the Knicker of Time!, Max goes off to find Nicholai when he insulted Norman after defeating May. He brought along a pile of berries which attracted the Zigzagoon's attention. They get angry when Max ran out of berries and Ash, May, Brock, and Nicholai arrive to save Max. When Nicholai led the Zigzagoon away from the group, Max apologized for his actions earlier.
Max takes a liking to Katrina's Poochyena in A Bite to Remember. Seeing that Katrina owned three Mightyena, Max attempts to get Poochyena to evolve. He trains it with Torchic but was unsuccessful due to Torchic attacking both Max and Poochyena. Max then ran off with Poochyena after Ash told him that some Pokémon are happy the way they are. When Poochyena was caught by Team Rocket, Max encourages it to bite through the net to free itself and the other Pokémon as well. Afterwards, Poochyena was able to evolve into Mightyena.
In Candid Camerupt, Max borrowed Ash's Corphish during the battle with Vivi, who had a crush on him. Since Corphish was Ash's Pokémon, Corphish recklessly attacked Marill even though Max wanted Corphish to go easy on Marill. This victory caused Vivi to no longer be interested in him.
Max meets a look-alike of his who has the same name in Maxxed Out!. Both of them were fighting when the brown-haired one criticized the green-haired Max about how skilled Trainers can only handle Skitty as he thought that the Skitty was his. Max meets up with the brown-haired Max by the lake when a Surskit was dancing around there. May suggested to both Maxes that they should be friends but it resulted in them fighting. When Team Rocket arrived with their goal in catching Surskit for the boss, the green-haired Max and the brown-haired one go off and find Surskit as it ran away. They find it in a new water spring located in the forest. When Team Rocket returned to capture the Surskit, both Maxes work together to take on the trio and Surskit finished them off. After Team Rocket's defeat, both Maxes become friends and the brown-haired Max promised the green-haired one that he will become a Trainer someday.
In Take This House and Shuppet, Max and the gang go to a mansion. He separated from the group after he got into a sibling rivalry with May when they both accused each other of ending up in the mansion. When Max was still upset about May, a Shuppet covered him with red aura and Max noticed it. They played with each other and Shuppet showed Max a secret room containing a playground. Still mad about May, Max had Shuppet play a prank on Ash, May, and Brock by lifting up items in the kitchen when the three were headed there. When Team Rocket was about to get May's Torchic, Max blocked their way until May arrived. Max stood back as May took things from there with her Torchic and was about to get crushed by a falling shelf until Shuppet saved them by lifting the shelf.
Max finds an injured Ralts in Do I Hear a Ralts?. He took it back to the campsite where Snorunt successfully cheered it up using Ash's hat and Max's glasses. Max takes Ralts to a Pokémon Center after Brock pointed out that Ralts was running a fever. While Ash, May, and Brock were battling Team Rocket while the latter was attempting to steal Ralts for their boss, Max made a run for the Pokémon Center with Snorunt tagging along. Along the way, Max dealt with Team Rocket again but they were stopped by Kirlia and Gardevoir. Max explained to them about Ralts's condition but Kirlia was about to attack him until Ralts protected him with Safeguard despite being in worse condition. Seeing that Ralts was willing to trust Max, Kirlia and Gardevoir teleport away. Max finally arrived in a Pokémon Center and reunited with Ash, May, and Brock. Max was happy to see that Ralts was healed up. However, he was sad to say goodbye to it after it left with Kirlia and Gardevoir.
In Pokémon Ranger - Deoxys' Crisis!, Max goes with the group and Solana to meteorite cave where they find out about a meteorite relating to Deoxys there. Max was willing to communicate with it and Deoxys takes him and Meowth to another dimension. Deoxys possesses Meowth as it explained to Max that it was scared during the space flight. Deoxys then explained to Max about the meteor landing and outer space, and that it was alone without a friend to hangout with. When Ash and his friends arrived in the cave again, Ash's Swellow and Sceptile, May's Combusken, and Brock's Marshtomp signaled their arrival and Max was happy to see them again. When Deoxys battled the group outside the cave, it caused some friction inside the alternate dimension that made Max and Meowth bounce around. However, they were able to get out with the help of May and Jessie. After the battle, Deoxys possesses Meowth again where it thanked Max for everything and flew off, wanting to explore the planet even more.
At the end of Advanced Generation, May announced that she wished to travel to Johto alone. This initially upset Max but Ash cheered him up with the promise of a battle between the two when Max becomes a Trainer. He arrived home in Petalburg City where he took lessons from his father and helped to look after the Gym Pokémon. Max has received just two cameos since his departure, triggered by May's brief return for the Wallace Cup arc.
Max later reappeared in a flashback in The Dream Continues!.