Unlimited shield
Pause the game while playing, then hold L1 and press Up, Down, Up, Left, Right, Down, Up.

Unlimited lives
Pause the game while playing, then hold L1 and press Up(3x's), Left(2x's), Right, Left, Right.

Cheats
Gather up all 400 fireflies in a level to the mentioned cheat available.

Level 1: Insect Eye. Changes your vision.
Level 2: Screen Switch. Reverses level.
Level 3. Auto-Hop. Hold D-pad to keep Zapper moving.
Level 4: Infinite Super Zap. Zapper always has a Super Zap.

Hints & Tips

Locate secret passages
Simply follow your friend's directions to find secret passages.

Win the round
Gather up six eggs in every round and win the round.

Flying
Be the victor in the first world with 400 points and you will be able to fly.