Unlockable: Neverending Stealth

At the code entry screen enter 53467.

Hint - First Boss

To defeat first boss you have to help the people with their things -- you don't have to help all the people, just enough to access the boss.

Then you go to where you started playing. You will see a purple spiral shape. Enter the spiral and say, 'yes' to start the boss fight with Colosal Inferno.

He will shoot fireballs at you. To avoid them, run right when the fireballs shoot left. Run left when the fireballs shoot right. Then stay away from the Colossal Inferno as far as you can. He will use his firebreath on you.

After that's done, there will be a light in the middle of it. Hit the light for about 5 seconds and run away. If you stay to long it will slap you. Keep doing this until the Colossal Inferno dies.

Hint - Aang'ed XP

In the first stage ('The Water Tribe') you will have a quest to help the old woman when the Fire Nation will start attacking. You will need to get to where Sokka is. Before you depart, you can stay in the vicinity and kill as many of the infinite Fire Nation enemies as you want for Aang's level to increase. This leaves you time for levelling other characters later.