All of Mikey's brothers fought over how Mikey should evolve his Eevee. Despite the fact that all of his brothers wanted to see him train an Eeveelution as well, he preferred keeping his Eevee just the way it was. However, he did not have the courage to tell his older brothers this. Eventually, after some advice from Misty, he decided to try anyway. His brothers eventually came to accept Mikey's choice after witnessing Eevee battle Team Rocket and emerge victorious.
Mikey trained an Eevee, which appeared in The Battling Eevee Brothers. At first, Mikey was too embarrassed of what his brothers may think, but later, he found out it was his choice to evolve it. It first appeared in a nearby forest, where Ash and his friends found it tied up inside a hollow tree with just food and water. Using its collar, they found out that it lives in Stone Town, so Misty picked it up to find its real owner. They found the Eevee brothers, who told them their younger brother Mikey was the owner. It eventually found Mikey. It was then revealed that the brothers wanted Mikey to evolve his Eevee into its different forms; he didn't want to evolve it and tried to hide it. Misty told him to stand up to his brother about how he feels.
Suddenly, Team Rocket appeared and stole it and all of the other Pokémon, as well as evolutionary stones. The group eventually found Team Rocket using leaking petrol and were able to free all of the Pokémon before sending Team Rocket blasting off. After the battle, Mikey told his brothers that he did not want to evolve Eevee, and his brothers understood that it was his choice. It was last seen in a picture.
Mikey wanted to join the Knights of the Evolution Stone like his brothers did. Rainer, Pyro, and Sparky told Mikey the only way for him to join the Knights of the E Stone was to evolve Eevee. Mikey proved he didn't need to evolve his Eevee by defeating his brothers in a battle. For a short period of time, Misty wondered if Mikey had a crush on her, as he made comments during a scene in which he was discussing his future with Misty, that could be viewed as flirtatious, such as "It's worth it to see you smile." However, Ash interrupted their conversation before Misty could determine more. In Welcome to the Big Leagues Mikey can be seen watching the Indigo Plateau Pokémon League on his television.
Mikey owns an Eevee that was supposed to be evolved for the Knights of the Evolution Stone. Mikey uses his Eevee against the battle with Sparky's Jolteon.