You Said a Mouthful!

While Ash and Co. continue their journey, they meet Anthony and his Pelipper, which is said to be the world's most powerful Pokémon. The reason is that his Pelipper knows Fire, Grass and Electric-type moves instead of only Water and Flying-type moves. How is Ash going to defeat Pelipper, and what are Anthony's Bellsprout, Magby, and Magnemite doing in Pelipper's mouth?