To unlock all normal circuits, enter the password X, Circle, X, Triangle, Triangle, Square.

On the password screen enter Triangle, X, Square, X, Triangle, O.

To unlock the super circuit and secret boarders, enter the password Triangle, X, Square, X, Triangle, Circle.

While the game is loading, use the d-pad to control the spinning X.

At the "loading" screen, you can stop the spinning X by tapping UP repeatedly. You must play with the timing to get it right.