Mikey's brothers all wanted to evolve Eevee, but Mikey hesitated in doing so. To keep them from forcing him to evolve his Eevee, he hid Eevee, tying him onto a tree until Ash, Misty and Brock found Eevee and brought it back to the address on its collar.
When Team Rocket attacked the brothers' evolution party, they defeated Mikey's brothers. Seeing that Vaporeon, Jolteon, and Flareon were in trouble, Mikey proved that Eevee was strong and defeated them in battle. Seeing Mikey and Eevee's power, they agreed that Mikey should not evolve his Eevee after all.