Team Rocket snuck into the Gym and encountered Gloom. James had Weezing try use Poison Gas on it, but failed and Gloom emitted its scent, knocking Team Rocket out. During the Gym Battle against Ash, Erika sent Gloom against his Charmander. Gloom emitted its scent, causing Charmander to faint from the smell. After Team Rocket set the Gym on fire, Gloom was still inside and was afraid from the fire. Ash tried saving Gloom, but it started emitting its scent. Ash held his breath and took Gloom, but noticed it didn't emit its scent, since it felt safe in his arms. Ash saved Gloom out of the Gym, which impressed Erika to give him the Rainbow Badge.
While running away from his Pikachu, to have it stay with the other Pikachu and be happy with others of its kin, Ash recalled how Pikachu, who was with Erika and Gloom, found out Ash disguised himself as a girl to enter the Gym.
Ash remembered Erika and Gloom at the end of his journey through Kanto and Johto.