The Japanese television show Pokemon Smash has recently finished airing and it confirmed the existence of a new Pokemon that is akin to Pokemon Red/Blue/Yellow's most famous legendary Pokemon, Mewtwo. Details of the new form are still scarce, but it appears linked to an upcoming Pokemon movie featuring Mewtwo and Genesect. Most likely, it is a new form of Mewtwo, similar to how Pokemon like Shaymin and Giratina have multiple forms.
"Do I look familiar?"
Below is the brief trailer of this new Mewtwo-esque creature in action within Pokemon XY, which will release worldwide this October.