Mewtwo has two Mega Evolutions, available in Generation 6 games. They can be activated in battle when holding the Mega Stones, Mewtwonite X and Mewtwonite Y respectively.

A complete list of Pokémon that evolve at specific levels, including additional conditions.

#229 Yveltal Dark · #230 Zygarde · Ground #231 Diancie · Fairy #232 Mewtwo Psychic

Gallery of Mewtwo sprites from each Pokémon game, including male/female differences, shiny Pokémon and back sprites.

Pokémon X & Y introduced a new type of evolution called Mega Evolution. When holding a particular Mega Stone (specific to each Pokémon), certain Pokémon can Mega-Evolve in battle.

FireRed & LeafGreen stick to the original 151 Pokémon of Red/Blue/Yellow, despite having introduced two new generations of Pokémon in the meantime, including evolutions of Kanto Pokémon.

Moves learnt by level up Mewtwo learns the following moves in Pokémon Red & Blue at the levels specified.

The game does not include evolutions or pre-evolutions from later generations such as Pichu, Crobat, or Umbreon, but it does include Alola Forms and Mega Evolutions of Kanto Pokémon.

#0147 Dratini #0148 Dragonair #0149 Dragonite · Flying #0150 Mewtwo Psychic #0151 Mew Psychic

Aug 31, 2014 · The most logical expectation might be that Mewtwo is almost a completely humanoid Pokemon, so it doesn't need a trainer to actually set itself into a mega form.