The game itself picks up from where the cartoon finishes, it seems it is just a few hours to complete. This is a nice multilanguage package including English, French, Deutsch, Nederlands. It seems to be very popular, so it's a rom that you shouldn't miss in your own collection.
Download link for Avatar - the Legend of Aang (Multilanguage)
Size: 3 MB
Platform: any GameBoy Advance emulator