Go on Single Player mode and you will see Event Matches mode.
Play 200 vs. matches or clear event match 37. Next you will fight Pichu in the Pokemon place!
From IGN.com "Clear Event Match 29 or play more than 600 Vs. matches. " A link to a guide to all unlockables in the game has been added below.
Beat event # 37 (Legendary Pokemon)
no
it means you have to play 600 matches in vs aka mutiplayer
Play as Marth on classic mode (no continues) or play 900 vs matches.
Complete Event 37, Legendary Pokemon. This event involves you facing 4 giant Wire Frames and Jigglypuff; with Poke Balls that contain nothing but legendary Pokemon. You can also unlock Pichu by doing 200 matches, and then defeating Pichu in a match.
It's not that the event doesn't work, it's either your disk or your GameCube that has an error.
finish the first adventure level when the seconds is a 2 and beat adventure or play 800 VS matches
play 1000 vs matches to unlock character 25, Mr. Game and Watch. There are no characters after that.
there are only 2 ways to unlock mewtwo on ssbm. 1) play 2 player for a total of 20 hours 2) play a bizzare amount of matches (i forgot how many but its a LOT!!!!)
jigglypuff- 50 vs. matches, clear classic or adventure dr. mario- 100 vs. matches, clear classic with mario pichu- 200 vs. matches, event 37 falco- 300 vs. matches, 100- man melee marth- 400 vs. matches, clear classic or a vs match with all 14 original characters young link- 500 vs. matches, clear classic 10 times ganondorf- 600 vs. matches, event 29 mewtwo- 700 vs. matches, 1 vs. match for 20 hrs. luigi- 800 vs. matches, clear adven. with time ending in X:X2:XX then finish adven. roy- 900 vs. matches, clear classic with marth mr game & watch- 1000 vs. matches, clear classic, adven., or target test with everyone