While at the main menu, press Up, Up, Y, Y, X, X.

Unlock Big Hear Mode

While at the main menu, press B, X, R, L, Right.

Unlock Unlimited Turbo

While at the main menu, press Down (3x), L, R, Z.

Unlock Tag Mode

While at the main menu, press Z, X, Z, X.

Unlock Small Mode

While at the main menu, press L, Z, Left, Right, B, B.

Unlock Little Gravity

While at the main menu, press Left, Right, Up, Down, B (3x).