If you haven't unlocked all the super smash bros melee characters except Mr Game & Watch, your out of luck. So unlock all characters before you go on.
To unlock Mr game and watch, you have an choices. Choice #1, you need to beat Classic witM all characters in the whole game besides MG&W (Mr. Game & Watch) (Any level/stock).
Choice #2, beat Adventure with all characters except MG&W. (Any level/stock)
Choice #3, beat every body's Target Test including mewtwo's. (If you do MG&W's Target Test, you unlock Dream Land Past Stage)
Choice #4, just play 1,000 VS Matches.
After you complete either of these choices, you will face MG&W in the stage Flat Zone. (To unlock this stage, you need to beat All-Star with MG&W. Also, you can unlock the stage The Battle Field, if you beat All-Star for the first time) Beat MG&W, and you will be able to be him as a playable character!
Beat Classic, Adventure, or Target Test with all charcaters to unlock Mr. Game and Watch.
To unlock him in melee clear target test with the first 24 fighters.To unlock him in brawl clear target test with 30 characters
Unlock all characters except mr game and watch then use mewtwo in classic mode and defeat master hand and then defeat mr game and watch to unlock him or use all the characters exept mr game and watch to do target test you must smash all the targets for each character then defeat mr game and watch or play 1000 matches in melee mode and then defeat mr game and watch.
play 1000 matches in melee mode and then defeat mr game and watch, use all characters except mr game and watch in target test and break all 10 targets for each character and then defeat mr game and watch, use mewtwo after unlocking every other character except mr game and watch in classic mode then defeat mr game and watch.
Play 1,000 melee matches in melee mode or beat classic mode with mewtwo after unlocking the other secret characters.
You have to get every character in the game.
In melee play 1,000 melees, finish target test with the 24 characters or beat classic mode with mewtwo then defeat mr game and watch to unlock him. In Brawl play 400 brawls or beat the subspace emissary if you choose the brawls you must defeat mr game and watch to unlock him.
beat classic mode with all playable characters, also you might be able to beat adventure mode with all characters to unlock him too.
Play 1,000 vs. matches, losing to any other hidden character that challenges you
...He throws sausages.
Action Replay.
Dr Mario, Young Link, Marth, Roy, Mr Game and Watch, Mewtwo, Falco, Ganondorf, Pichu, Luigi, Jigglypuff.