Kyuubi Naruto-After you obtain Rock Lee, complete the game twice with every character in the 1-player mode. When you have done that, a message tells you to press the Z or X button during the character select screen(for all modes of play) when the cursor is over Naruto.
Rock Lee-To play as Rock Lee, complete the story mode up without continuing up to the fight with Zaibuzan. After defeating Zaibuzan, Rock Lee would challenge you. Defeat him and the story ends after another scene. You are now able to select him in the other modes.
Sharingen Kakashi-complete the game in 1 player mode with Kyuubia Naruto. Then complete the game with Kakashi again. A message now tells you to press the Z or X button during the character select screen(for all modes of play) when the cursor is over Kakashi.