Alternate Costumes:
On the character select screen, highlight a character and press Y.
Unlock Sound Test:
Beat the game with every default character.
Unlock Hinata:
Clear story mode using Sakura. Find this fighter by highlighting Rock Lee and pressing X.
Unlock Extra Characters:
Rock Lee
Beat Zaibuzan in story mode without using continues, and then beat Rock Lee when he appears.
Kyuubi Naruto:
Unlock Rock Lee, and then beat the game with all characters. Now highlight Nartuto on the character select screen and press X or Z.
Sharingen Kakashi:
Beat the game with Kyuubi Naruto, and then beat the game with Kakashi. Now highlight Kakashi on the character select screen and press X or Z.