just complete classic with sonic on any difficult

Luigi – Clear Adventure on at least normal with Mario
Jigglypuff – Clear Adventure on any difficulty with any character.
Cloud – Complete 100-man melee with any character.
Crono – Clear 3-minute Melee.
Naruto – Clear Adventure with the original 13 characters.
Shadow – Clear Adventure with Sonic, Tails, and Knuckles
Super Sonic – Clear Classic with Sonic on Very Hard Difficulty without getting Game
Over. (Known glitch that you may be on any difficulty and it will still work)
Zero – Clear Adventure with Megaman on at least Normal Difficulty without getting a Game
Over.
Young Link – Clear Classic with Link on any difficulty.
Inuyasha – Clear Adventure without losing any lives.
Mr. Game and Watch – Clear Target Test with every character but him.
Mr. Incredible – Clear Classic Mode with the original 13 characters.
Mewtwo – Clear Adventure with Pikachu and Jigglypuff.
Lloyd – Clear Adventure with any character after having one hour of total play time.
Blue – Clear Adventure with Blade on at least Normal difficulty.