Successfully complete the normal games, then finish the Arena. A sound test option will become available.
Reduced damage
Pause game play in any level except for "Milky Way Wishes" and quickly press L, R(2), L, X, A. The majority of opponent attacks will now be half as effective.
Invincibility
Pause game play and quickly press R(3), L(3), A, B, A, B, A, B at the start of a level.
Kill monsters in one hit
Press Up, Down, Left, B at the selection screen.
In-game reset
Hold L + R and press Start.
Hint: Heal your Kirby's helper
Throw away the Special skill and allow the Helper to touch it. He will transform and his health will be restored.
Hint: Kirby's helper self-destruct
Have the helper continuously press A to begin flashing and die. This is helpful when playing in two player mode, when the Kirby player has a skip that he or she wants to keep. The helper can do this, then touch the enemy with the desired power.
Hint: Copy Vision ability
Locate the large diamond shaped green star in Milky Way Wishes. Approach the star and press the button to enter a level. Complete the level to get the Copy Vision ability.
Hint: Fire ability
The fire ability can be found after the very first part of the Hotbeat level. The large space filled with lava/coals has a door in it. Hit the bomb block to create a space. Full or very high health is required for this next step unless the "Invincibility" code has been activated. Enter the space through the lava. You will get burned at least two times. Go through the space, and the fire ability will can be obtained inside (after defeating a few Burnin' Leos).
