In Vs. Com mode, hold L + R and press A for a more challenging opponent. Hold L + R and press B to set the difficulty level to the highest setting. Repeat the code to disable its effect.
Panel De Pon: Level select
Hold Z and press B, A, L, A, B, A, L, A at the Panel De Pon title screen.
Panel De Pon: Super hard difficulty
Select single player vs. Com mode. Enter the level selection screen, then hold Z and press L(2), A, B.