Finding Nemo cheats and cheat codes for Gamecube

Press the following button combinations at the title screen after
pause game play to access the the cheat options.

Credits:
Y, B, X, Y, Y, B, X, Y, B, X, Y, B, B, X, Y, B, X, Y, B, X, X, Y, B, X

Invincibility:
Y, B, B, X, X, X, Y, Y, B, B, B, X, X, X, B, Y, X, X, X, B, X, Y, X, X, B,
X, X, Y, X, B, X, X, X, Y

Level Select:
Y, Y, Y, B, B, X, B, Y, X, B, Y, B, Y, B, Y, X, Y, Y

Hidden Level:
Y, B, X, X, B, Y, Y, B, X, X, B, Y, Y, X, B, Y, B, X, X, B, Y

Secret clue
While on the Mount Wannnahockaloogie level, look for an old brown sign.
Dart behind the sign to score an important clue.