Cheat Mode
Go to Ember Islands Game Secrets and enter the following codes at the "Code Entry" screen:
Momo-Sokka-Toph - Appa (CHIBI) appears at the volleyball theatre.
Pakku-Iroh-Appa - Azula (CHIBI) appears at the volleyball theatre.
Aang-Katara-Zuko - Momo (CHIBI) appears at the volleyball theatre.