Shark Tale - Attack mode on at all times

Invincible Oscar:
Hold L and press A, X, A, Left2, Y, R, Down, Y2 at the controller selection screen.

Replace all Pearls with Fish King coins:
While playing on any level with Pearls, press Select, then hold L press X, A, X3, A, X2.

Chapter 3: Pearls
If you attack a puffer fish, many pearls will come out.

Chapter 9: Avoid being caught
To avoid being caught by police fish, go into houses until the cops pass.

Chapter 9: Staying Hidden
When you must sneak around the fish with lights on their heads or the ones with torches, there are some tables with cloths on them that you can go under without being detected.

Completing Dance Mode:
To complete dance mode easier, press A B X Y on each arrow. It will count as the arrow that is pointing to, even doubles.

Shorties:
If you cannot beat the Shorties, try following them.

Two extra Clams and fame:
While playing a game, press Select, then hold L and press X2, A2, X, A, X2.