While on his way to the Indigo Plateau, Ash was stopped by Otoshi, who challenged him to a battle, but with a twist: whoever lost had to give up their badges to the winner. Ash, confident he would win, accepted the challenge. Otoshi's Marowak successfully defeated Ash's Bulbasaur, but it lost to Pikachu.

Otoshi then admitted that he had no badges to give to Ash. Ash thought that Otoshi was a cheater, but then he told the story of how his badges were stolen by somebody who he didn't know. He claimed a talking Meowth did it. Ash and his pals knew Jessie, James and Meowth of Team Rocket were the ones who robbed Otoshi. Feeling sorry for him, Ash and the others decided to help Otoshi retrieve his badges from Team Rocket.

In the meantime, Marowak ran away from Otoshi, saying that if Otoshi were a more responsible Trainer, he would never have lost the badges. Otoshi was saddened, but continued to look for his badges.

After Ash, Misty, Brock and Otoshi confronted Team Rocket, Otoshi challenged Jessie for the badges. She told Otoshi that if he defeated her, she would give his badges back. Using his Doduo, he tried to defeat Jessie's Arbok, but the two heads ended up fighting with each other. Jessie was about to capture the Doduo, when Marowak returned to Otoshi and helped him defeat Jessie.

Otoshi, now reunited with both Marowak and his badges, continued to the Indigo Plateau to compete in the Pokémon League.