Big head mode
Pause the game, then hold Select and press L1, Up, Right, L2, Up. Release Select, then hold Select again and press L1, Up, Right, L2, Up.

01/11/00 Unknown

All Dream Keys
Enter this code at the House hub. O, L1, L2, L1, L2.

All Winks
Enter at House Hub. Left, Down, Right, Right, Right.

Reset Moons
Enter this code anywhere - Up, L2, Left, R2, Left.

Reset Z's
Enter this code anywhere - Right, L1, Up, R1, L1.

All Cogs
Enter this code anywhere - Down, R2, L1, Up, R2.

Reset Lives
Enter this code anywhere - L1, Up, Right, L2, Up.

12/23/00 Unknown