Pokémon Season 5 Episode 38

On meeting up with a proud Pokémon trainer who dares all comers to face his Poliwrath, Misty and Ash quickly rise to the challenge. Misty, in particular, encourages her Poliwhirl to watch closely as it may someday evolve into a Poliwrath. As is often the case, the battle isn’t long over before this challenger and Ash and Misty have become fast friends. Meanwhile, Team Rocket, having furtively observed this battle and been convinced that the Poliwrath is a match even for Pikachu, decide to first capture it and then use it to capture Pikachu. Unfortunately, this logic does not hold as they find capturing a Pokémon stronger than Pikachu even more difficult than simply capturing Pikachu. A surprise is in store for Misty, as her Poliwhirl evolves not into a Poliwrath, but into another Pokémon altogether.