Mewtwo

Mewtwo is a playable character in Super Smash Bros. Melee. In the Pokémon series Mewtwo is an artificial Legendary Pokémon based on the genetic code of the Legendary Pokémon Mew. Due to constant experimentation, it went out of control and escaped. Mewtwo is commonly called the "Dark Side of Pokémon", which makes it one of the three evil playable characters in Melee. The other two are Bowser and Ganondorf, of the Mario series and The Legend of Zelda series, respectively. However, Mewtwo only appeared as a villain in Pokemon the First Movie, not in the video games, and in the movie he saw the error of his ways, meaning that he isn't a truely evil character.

Super Smash Bros. Melee
In Super Smash Bros. Melee Mewtwo is an unlockable character. Mewtwo appears after the player has played a total of 20 hours in VS matches and then battles the match's winner. If the player defeats Mewtwo, then it is unlocked.

Mewtwo is a somewhat heavy character, but has a high air jump (judging that its a Psychic Pokémon). Its attacks are powerful, but it is not very fast. It also floats above the ground, making it an easy target to be sent flying, and has low traction. Although these attributes make it difficult to control, it is incredibly powerful once used right.

It is currently unknown if Mewtwo will return in Super Smash Bros. Brawl.

Mewtwo does not use its hands to hold items, but uses telekinetic powers instead, making the items hover before it. A similar style is seen when Mewtwo hangs on a cliff or grabs another character. The only time it does touch an item is when floating on the Parasol. Mewtwo was voiced by Masachika Ichimura in both English and Japanese. Additionally, all of Mewtwo's voices are grunts, or evil laughs.

Classic
''A genetically created Pokémon, Mewtwo is the result of many long years of research by a solitary scientist. Although Mewtwo was cloned from the genes of the legendary Pokémon Mew, its size and character are far different than its ancestor. Its battle abilities have been radically heightened, making it ruthless.''

Adventure
''As Mewtwo relies mostly on its powerful brain, there are times when it scarcely uses its arms and legs. Since Mewtwo spends much of its time floating, it flies far when struck. Shadow Ball traces a jagged path once released: the longer Mewtwo holds it, the more powerful it becomes. Mewtwo uses Confusion to spin its foes around.''

All-Star
''Mewtwo is definitely not a speedy character, but its ESP-powered grab and throw moves are comparatively strong. Teleport has a short range, but doesn't leave it open to attack. It's best used as an escape move during disturbances. Mewtwo can daze a foe if it makes eye contact and uses Disable; the move is useless unless Mewtwo is facing its enemy.''

Trivia

 * It has no gender, being an experiment. It should be noted that not all Pokémon have genders.