Mewtwo is a Legendary Pokémon.
After completing the Cerulean Cave, Emile encounters Moltres at the end of the first half of Episode 51.
In the second part of Episode 52, Emile battles Mewtwo and tries to catch it. It was caught in an Ultra Ball after 3 hours and 15 minutes.
A Pokémon whose genetic code was repeatedly recombined for research. It turned vicious as a result.