Pokémon The First Movie

Pokémon: The First Movie: Mewtwo Strikes Back, commonly referred to as Pokémon: The First Movie, originally released as Pocket Monsters the Movie: Mewtwo Strikes Back! (劇場版ポケットモンスター ミュウツーの逆襲 Gekijōban Poketto Monsutā: Myūtsū no Gyakushū), is a 1998 Japanese anime film directed by Kunihiko Yuyama, the chief director of the Pokémon television series. It is the first theatrical release in the Pokémon franchise.

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An invitation with a mysterious woman on it is sent to Ash and his friends to come to New Island and battle the worlds strongest Pokémon Master. Once they get there they realize that not only that the worlds strongest Pokémon Master is Mewtwo, but the mysterious woman is a Nurse Joy who went missing from a Pokémon Centre. She is mind controlled by Mewtwo so he can gain knowledge of Pokémon Physiology from her.