It starts out as playful as Aang is the Avatar (the only person in the world who is linked to the spirit world and can master all 4 elements - making him the most powerful person in the world) was frozen for over 100 years and he still remains 12 years old. He wants to have fun but the world needs him to grow up and fight the Fire nation.

He has fits of immaturity (comic relief) a crush on the cute waterbender girl, but he can be possessed (put in the avatar state) when in great danger and wield unimaginable powers.

The course so far has made him more serious and driven to fight to save the world - as he runs from the fire nation.

The plot is very well written and executed (no need for movie ruining trick endings like shamanamalalanan). The characters develop very well and you can relate to many and see their viewpoint. There are some episodes where you see the world from different views even the 2 main animals (Momo & Appa).