New Mewtwo-Like Pokémon Revealed For X And Y - Game Informer

The official Pokémon X and Y website has been updated with a new Pokémon that is "strangely familiar".

Pokémon X Preview - New Pokémon X & Y Trailer Reveals Trainer Customization, New Mewtwo Mega Evolution - Game Informer

New Mewtwo-like Pokémon revealed for Pokémon X, Pokémon Y - Polygon

Getting Mewtwo and other tips and tricks for Pokémon X and Y

Latest Pokemon Unite leaks hint at Mewtwo Mega form release date and license cost

A more detailed CoroCoro leak has been posted on Serebii. Now with in battle screenshots of the mega Pokémon. : r/pokemon

JEFusion Japanese Entertainment Blog - The Center of Tokusatsu: Mewtwo Awakens with New Form in Pokemon X/Y Version

Pokemon X & Y - New Mewtwo-Like Pokemon Revealed (Mewthree?)

Pokemon X - Nintendo 3DS, Nintendo 3DS

New Mewtwo-like Pokémon revealed for Pokémon X, Pokémon Y - Polygon