When Ash and his friends were on their way to Mossdeep City, they arrived onto Muscle Island and met Rocky who made his home there. Rocky enjoys exercising, and uses Pokémon to help him. While his friends on the island were exercising, he shouted some encouragement to them. He introduced himself to the group and asked Ash about his journey. He showed the group around to the island where the Trainers there were exercising. Rocky invited them to join along in which they agree, except for May, but May joined them later on. Rocky assigned Ash and his Pikachu to another mechanism and Brock watched on.
Another one of Rocky's hobbies is battling. Rocky requested Ash for one and they went to the beach area of the island. Rocky challenged Ash to a Double Battle as his friends continued their training on Muscle Island. Rocky, using his Walrein and Quagsire, was able to get the upper hand in his battle against the young Pokémon Trainer by having the half-Ground Quagsire block all of Pikachu's Electric moves and having his Walrein use Ice Ball. However, Ash was able to deduce that the speed of the Ice Ball slowed down every turn. Using it to his advantage, he was able to defeat Rocky. Rocky complimented on Ash's strategy and May, Max and Brock then showed up. Rocky then pointed out a ferry to Mossdeep City for the group to take and the group went on board.
| Walrein was called out for a Double Battle against Ash. Around the first turn, it used Ice Ball and in every turn, the move got stronger. Ash saw that Ice Ball got slower every turn and turned the tables on Rocky by having Pikachu dodge. Walrein was defeated after Quagsire fell for Grovyle's Leaf Blade and left itself wide open for Pikachu's Thunderbolt.
Walrein's only known move is Ice Ball.
| Quagsire was called out for a Double Battle against Ash. It was in charge of blocking electric attacks from hitting Walrein. It was defeated after getting hit by Grovyle's Leaf Blade.
None of Quagsire's moves are known.