Mewtwo

Mewtwo is a Psychic-Type Pokémon. It appears as an unlockable character in Super Smash Bros. Melee. Despite being classified as a middleweight character, it has very little traction, but Mewtwo can be effective when on the defensive. Mewtwo's special moves are quite useful, once mastered, and have powerful and useful effects. Mewtwo has appeared in Melee, but his inclusion in Brawl is unknown. Mewtwo's inclusion is, however doubtful, since in the japanese ad suggesting Ness, Jigglypuff and Lucario's inclusion, a sticker appears which applies to every pokemon character but Mewtwo, Mewtwo's removal is suggested by this.

SSBM

 * B - Shadow Ball (Much like Samus's Charge Beam, Mewtwo charges up and sends it flying in a wobbly path. Note: If an enemy touches the ball while it is charging, they will take damage.)
 * B → - Confusion (Puts the foe on their backside and can reflect projectiles.)
 * B ↑ - Teleport (This move can't make Mewtwo warp through solid platforms, but it can get Mewtwo out of a tight spot.)
 * B ↓ - Disable (Can disable enemies temporarily . Note: This move can be reflected back at you. Your opponent must be facing you in order to work.)

Unlocking
Mewtwo can be unlocked by playing more than 20 combined hours in Vs. Mode or after having played more than 700 Vs. Mode matches.

Classic Mewtwo trophy
To unlock this trophy, you must complete classic mode as Mewtwo.

Red Smash Mewtwo trophy
To unlock this trophy, you must complete adventure mode as Mewtwo.

Blue Smash Mewtwo trophy
To unlock this trophy, you must complete all-star mode as Mewtwo.

Super Smash Bros. Brawl
It is rumored that Lucario will replace Mewtwo in Brawl, but of course, this is just a rumor.