100%(Because it was seen following Pikachu when he was running away.)
The Mewtwo Ball is a specialized Poké Ball used by the PokémonMewtwo in order to capture the Pokémon whose trainers were selected to go to New Island. Its main purpose is to allow the captured Pokémon to become cloned for Mewtwo's army in order to fight against the originals. The Mewtwo Ball can also capture Pokémon already stored within ordinary Poké Balls, and are able to pursue Pokémon, as if flying. Once the cloning process is complete, the Mewtwo Balls release the captured Pokémon. Togepi was the only Pokemon not to get captured because Misty put it in her bag.
The Mewtwo Ball is primarily black in color and has an eye-shaped object positioned directly in the center of the sphere. There is a grey outline around the eye embedded in the center, which travels around the circumference of the Mewtwo Ball. There are two purple stripes racing down the upper half of the Pokéball.
The title Mewtwo Ball is conjectural due to the fact that it was never named during the course of the movie.