Junichi Masuda appeared on Pokémon Smash 50 to announce further details about the Mewtwo event revealed by Shoko-tan on Pokémon Smash 49. The event distribution will take place from September 26th, 2011 until October 31st, 2011 on the Japanese Nintendo Wi-Fi Connection for players of the Japanese versions of Pocket Monsters Black & White. This Mewtwo has PokéSma! (ポケスマ!) as its OT, has the Pressure Ability, has a Premier Ribbon, comes in a Premier Ball, is holding the King's Rock item and knows the moves Psystrike, Shadow Ball and Aura Sphere. Mewtwo has a fourth move but it won't be announced until episode #51 of Pokémon Smash, which airs September 25th, 2011.


Source: http://www.pokemon.co.jp/ex/mewtwo/feature/index.html#feat01

Well, the high level moves have already been covered, so clearly the last one is some kind of super-special move.