Level Select
Pause the game and hold L, then press Y, Right, Up, X, Y, Left, Up, X, Y. The screen will shake if you correctly entered the code.
Submitted by Abe. 

Slow Motion Mode
Pause the game and hold L, then press B, Right, Up, Down, B, Right, Up, X, Y. The screen will shake if you correctly entered the code.
Submitted by Abe. 

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