here is a guide for getting the charecters ^^
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.
Zero - Clear Adventure with Megaman getting Game Over on at least Normal Difficulty.
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
hope it helps