Unlock Kakashi.
In order to unlock Hatake Kakashi beat the game with both Naruto and Sasuke

Unlock Sound Test Mode
To successfully unlock the Sound Test Mode, just collect all 100 Leaf Symbols and it'll appear on the Main Menu.

Unlocking Gaara
To fight the hidden Boss Gaara, beat the game with somebody and then start over as them. The levels will change, and the final boss will be Gaara

2nd Mission
Beating the game one time with any character will unlock a 2nd ''night-time'' mission for that character. The levels will remain the same, but the final 3 bosses are different.

Portrait Gallery
Beating the game one time will unlock the portrait gallery, where you can view portraits for all the characters you meet, and the bosses you've beaten.


Secret Jutsus
On the Leaf Village Arena level, 1st Area (first level where you get the wind scroll) near the end of the level, you will fight a jounin-level enemy (big green ninja) and to the right of the platform he is standing on, there is a small crawl-way. Inside of the room, there is a large invisible scroll. When you acquire it, that character will permanatly learn level 4 Jutsus (if you save your game.)


Naruto
Red - Uses Kyuubi to heal himself.
Yellow - Uses Kyuubi to heal himself, then deals damage to all enemies on screen.

Sasuke
Red - Preforms an upward kick-aerial combo.
Yellow - More powerful version of the red combo.

Kakashi
Red - Preforms Chidori, hits all enemies on screen.
Yellow - More powerful version of red jutsu.


Special Jutsu Finish
Use Naruto's Naruto Rendan (3rd special) in the red part (causing him to fail) against Kiba. Naruto will fart and cause Kiba to be paralyzed then Naruto will finish it up with Naruto Rendan.


Special Jutsu Finishes
Certain bosses are dealt extra damage when certain Jutsus are used on them.

Using Naruto's Harem no Jutsu on Ebisu will cause Ebisu to have a bloody nose and die instantly.

Using Kakashi's Dog Summoning no Jutsu on Zabuza will make all the dogs latch on to Zabuza, and Kakashi will preform Chidori on him, just like in the anime and manga.

Using Naruto's Harem no Jutsu on the 4th Hokage at the end of the final level will make give him a bloody nose also