From Bulbapedia, the community-driven Pokémon encyclopedia.
Poncho (Japanese: ポンチョ Poncho) is a character of the day who appeared in Go Go Ludicolo!.
Poncho met up with Ash and his friends in the middle of a forest near North Petalburg. He challenged Ash to a battle, saying that if Ash won, Poncho would buy them cheeseburgers in the next town, while if he won, Ash and his friends would have to give him their sandwiches. Ash accepted the challenge. He was originally going to use Grovyle, but Corphish, being jealous, stepped up to battle Poncho's Ludicolo.
Corphish ended up losing the battle, but it refused to accept its defeat. It followed Poncho and Ludicolo into the forest, wanting a rematch. Before Poncho could reply, Team Rocket stole him and Ludicolo. Corphish was able to set them free and send Team Rocket blasting off. Impressed with how strong Corphish was, Poncho agreed to share the sandwiches he received with Ash and his friends.
Poncho and his Ludicolo battled using dancing techniques. Poncho would play his conga drum while Ludicolo was in battle, which encouraged the Pokémon to move about to dodge attacks. Ash felt that Poncho should have kept the dancing to himself.