Super Smash Bros. Melee Unlockables

Finish the game in classic mode as Mario.

Finish the 100 man melee.

Finish event mode Triforce Gathering (29) to unlock Ganondorf.

Finish the game with any character under any difficulty setting. Continues are allowed.

Finish the first stage of adventure mode with a time of 3:32:99 to 3:32:00. You will have to battle Luigi and defeat him in under one minute. Finish the remainder of adventure mode. At the end of adventure mode you will fight Luigi. Defeat Luigi and he will become a playable character.

Mewtwo will appear at random at the end of a multi-player match and challenge the winner. He will be unlocked as a selectable character after he is defeated. Or in versus mode, play 700 battles or get a total of 20 hours of game play.

Play Vs. mode with all 14 default characters {you dont have to win}. It has been reported you need to beat the game with all default characaters.

Finish the target test mode with all of the other 24 characters.

Another way to get Mr. Game & Watch is to beat classic with all the characters.

Do one of the following:

Unlock both Luigi and Falco to unlock event mode #37 (Legendary Pokemon). Finish event mode #37. After winning, Pichu will become playable.
Finish adventure mode as Mewtwo.
Play 200 matches in versus mode.