Rudy is the Gym Leader of the Trovita Island Gym which is a gym located on an island just off the coast of Trovitopolis. Any trainer who can pass his 'attack test' and defeat in in a Pokémon battle will earn the Spike Shell Badge.
When Rudy battled Ash, the rules were that Rudy would choose Pokémon of the same type as Ash. So Rudy's Electabuzz went up against Pikachu, Exeggutor against Bulbasaur and Starmie against Squirtle. Rudy has a Pokémon in his gym that would cover every Pokémon type except ghost (and the new types added in the Gold & Silver generation).
Rudy uses dancing techniques to improves a Pokémon footwork and agility. Rudy himself also enjoys to dance.
Rudy's younger sister lives on Trovita Island along with Rudy and a few additional trainers.