Mewtwo is a powerful psychic-type Pokémon created using Mew's DNA.
Mewtwo is a partial clone of Mew. It was created by Team Rocket scientists from Mew's DNA, but this only proved to be partial in creation, since they didn't have enough of Mew's cells. However, its DNA was spliced multiple times to ensure a successful cloning, This granted Mewtwo the genetic cells of Alakazam to increase its psychic ability, as well as Persian DNA to help maintain a strong enough body to handle the psychic strain. To complete this creation, Blaine, the leading scientist on the project, gave some of his own cells so that it could be complete. A monster was born. Mewtwo is known to be one of the most savage Pokémon that ever lived.
Mewtwo makes its first appearance when Blaine, a Gym Leader, tells of how an experiment using Mew's DNA went wrong, and the Pokémon escaped. Blaine used some of his own cells to make Mewtwo, and Blaines left arm is affected by it, more and more. Red encounters a destructive tornado, which is spawning from a cave, and checks it out. What he finds is that Mewtwo is at the base, generating a very powerful Psywave. Red tries to attack Mewtwo, but the attacks end up hitting the swirling Psywave, are carried around, and shot back at the attackers. The Psywave, known as Mewtwo's ultimate offense and defense. Blaine joins the near defeated Red, and Blaine tries to do a full power assault at Mewtwo. It is successful at breaking through to the eye of the tornado, and causing a massive explosion. In the rubble, Blaine is badly wounded, and Mewtwo gets up, wounded, but not much. Red tries to attack it in one on one combat, but Mewtwo makes a large, Psychic spoon, which is the ultimate weapon for one on one battles. Blaine manages to get back up, shows Red the only way to defeat Mewtwo, with a Master Ball, and warns him that if he uses all of his Pokemon to attack again, Mewtwo will just make another Psywave. Red tries it anyway, and Blaine sees that defeat is near. But he was wrong. Ash has a plan, a chain of Pokemon get Pikachu closer and closer, until Pikachu gets to the eye and touches Mewtwo with the Master Ball in its mouth. Mewtwo is captured.
Blaine trains with Mewtwo, and the two become one, with their motions. Later, when Red and the others are in danger, Blaine comes again, against the evil Elite Four member, Lance, the dragon master. Mewtwo proves to be a match for Lance's entire team at first, but soon finds that Lance is too much. Mewtwo can only remain out of its Pokeball for 3 minutes before Blaine's arm begins to go haywire, and Mewtwo retreats inside its pokeball to stop the pain of its master. Blaine and Mewtwo survive the battle, and live to see another day.