Mewtwo is a fictional creature from Nintendo and Game Freak's Pokémon media franchise. Created by Ken Sugimori, it first appeared in the video games Pokémon Red and Blue and their sequels, and later appeared in... wikipedia.org
Definition #2 for "mewtwo"
Mewtwo is a Psychic-type Pokémon who debuted in the first generation of Pokemon games released in 1996. It is one of the most powerful Pokémon in the series and one of the most popular, having played the role as the antagonist in the first Pokémon movie and appeared in several other Pokémon and Nintendo games.