I-Ninja Cheats (GameCube)

During gameplay, press START and enter any of these codes:

Sword Upgrade - Hold L BUTTON + R BUTTON, X, B, X, Y, Y, B, X, B

Complete Current Mission - Hold R BUTTON, B, B, B, X, Release R BUTTON, Hold L
BUTTON, Y, Y, Release L BUTTON, Hold R BUTTON, B, B

Big Heads - Hold R BUTTON, Y, Y, Y, Y, Release R BUTTON, Hold L BUTTON, Y, Y,
Hold R BUTTON + L BUTTON, Y, X, Y

The order of belts the Ninja will recieve is:

White

Yellow/Gold

Green

Blue

Red

Black

You must earn a certain number of Grades to get the next belt.

 

To get all the grades first you finish a level then get the next belt so 
sensie will let you in. Don't worry the level will be the same but there 
will be some extra thigs you have to do.

If you are having a hard time beating those minibosses, then here's your 
help. First, always press left, right, down, or up and x at the same 
time to dodge that swors throw thingy. Then after he throws his sword 
and he does not have it go in and keep pressing square. 

Don't worry, his sword cannot hurt you.

To unlock the Battle Arena, get all the grades, then you should get 
  the master grade. The Battle Arena will now be open in Robot Beach.