Skip Levels
Access the pause menu and enter these codes to advance to the desired level. Use "C76564J" for Level 2, "L88R8TC" for Level 3, "Y539WZG" for Level 4 and "NTTJ9KY" for the final level.
Old Cape
Batman will obtain new suits to use in the game, each with different functions and purposes. To revert to the old suit, pause and then hold "L" as you press "C-Left," "Down," "Up," "C-Right." You can only use gadgets with this standard suit and you begin with 15 Batarangs. You also get the Nun Chaku, which does massive damage if you charge it.
Flight Mode
Access "Flight Mode," which give you an overhead view of the action, with another code. After pausing, press "Up," "Down," "Left," "Left."
Defeating Joker
At the end of Level 5, "Jolly Jack Candy Factory," you will square off against Joker. If you have plenty of lives remaining, just rush Joker and use Shield Punches to defeat him. If your extra lives are sparse you should use a more tactical approach. A satellite beam will track you, so run around to dodge this. Block any projectiles that Joker shoots at you and dodge the robot that follows you when it begins to spark. When you see an opening, move in and attack Joker.