What subtitle identifies the first Pokémon animated film?

Mewtwo Strikes Back is the subtitle of the first Pokémon animated film.

The film was released in Japan on 18 July 1998 under the title Pokémon: The First Movie. Its story centers on Mewtwo, a genetically engineered Pokémon created from research involving Mew, who challenges Trainers and questions the meaning of identity and existence.

Ash, Pikachu, and their friends are invited to New Island by a mysterious Trainer. The invitation leads to a confrontation involving cloned Pokémon and Mewtwo’s plan. The theatrical feature was paired with the short Pikachu’s Vacation in many releases, which is why some references describe the program as containing more than the main story.

The film’s title is often shortened to Pokémon: The First Movie, but “Mewtwo Strikes Back” is the specific subtitle. A computer-animated remake, Pokémon: Mewtwo Strikes Back—Evolution, was released in 2019.