How do you unlock Mewtwo in Super Smash Flash 2

Mewtwo is not in Super Smash Flash 2. The characters that are in the game are:

CharacterUniverseBlack MageFinal FantasyCaptain FalconF-ZeroDonkey KongDonkey KongFoxStar FoxGokuDragon BallIchigoBleachKirbyKirbyLinkThe Legend of ZeldaLloydTalesMarioMarioMega ManMega ManMeta KnightKirbyNarutoNarutoNessMother (EarthBound)PeachMarioPikachuPokémonSamusMetroidSnakeMetal GearSonicSonicSoraKingdom HeartsTailsSonicWarioWarioYoshiYoshi