Mewtwo was first introduced in Pokémon Red and Blue as a genetically engineered species.
In the games’ story, scientists create Mewtwo after conducting genetic experiments connected to Mew. The creature becomes too powerful to control, escapes from the laboratory on Cinnabar Island, and later waits in Cerulean Cave as a major post-game challenge.
Mewtwo and Mew are frequently confused because their names and story are closely linked. Mew is a mythical Pokémon associated with an ancient genetic lineage, while Mewtwo is the engineered result of scientific experimentation. Ditto is also sometimes connected to fan theories about Mew, but the games do not identify it as Mewtwo.
Mewtwo is a Psychic-type Legendary Pokémon. It later received two Mega Evolutions, Mega Mewtwo X and Mega Mewtwo Y, in Pokémon X and Y.