Enter these cheats on "Cody Entry"’ in the "Extras"

Every time you are in battle you can go back later to get more experience. Basically you can get unlimited experience.

This is the machine you must fight in order to find Katara. Dodge the fire bending. Try running left to right, then right to left. Continue this until you see a flashing light near it. This is your chance to attack. Hit it with Aang. You may use a Chi attack but just a plain attack should work just as well, however it takes time. You will have Saka (Katara’s brother) fighting with you to do double damage. After about a quarter way down on HP, the machine will start throwing fire around. Keep a safe distance from this attack. It causes no real threat to your or your partner as long as you stay as far away as possible.

You can wait for it to stop attacking, or you can attack it, which will barely affect it. Once it is done attacking, you must attack the sides which turn red.ong as you stay as far away as possible.