Bucky was a young trainer who went to visit his grandpa. When he came back into town, everyone had a Dunsparce but him. As Ash, Misty, and Brock heard the story and wanted to help Bucky to catch a Dunsparce. They encountered one, who went away and was blasted along with Team Rocket. The heroes decided to find a new one, but Team Rocket captured all the other Dunsparce. The heroes defeated Team Rocket, allowing Bucky to capture Dunsparce using his Caterpie.
Caterpie is Bucky's Pokémon. He tried to use it in a small contest with other Dunsparce, but Caterpie failed. Still, Bucky's Caterpie fought Dunsparce, allowing Bucky to catch it.