Secret Levels: 

At the game mode selection screen, press UP to 
enter a Secret Mode screen that should be empty. 
Do these footsteps to get the secret modes in 
this order....

Another: Up, Up, Down, Down, Up, Up, Down, Down

Maniac: Left, Left, Right, Right, Left, Left, 
Right, Right

Double Another & Maniac: Up, Up, Down, Down, Left,
Right, Left, Right

Mirror Another & Maniac: Left, Right, Left, Right,
Left, Right, Left, Right

The secret modes will then be saved to your memory
card so you don't have to do them again.