Zuko was one of the last characters added to the show. The Fire Lord was originally meant as the show's main antagonist, but the writers realized he would not be able to cause Aang and his friends trouble sitting from his throne. Zuko was then written into the show but became a major character arc.
Mako, who played Uncle Iroh, passed away while recording his parts for the last seven episodes of season 2. They had to quickly re-cast the part of Iroh. The re-casting put a halt to production on season 3. Greg Baldwin succeeded Mako's part in the third season.
The elemental bending movements are based on martial arts. Earthbending: Hung Gar Kung Fu; Firebending: Northern Shaolin Kung Fu; Waterbending: Tai Chi; Airbending: Baguazhang.
The calligraphy on the top and bottom of the map forms a rhyming couplet when read aloud in Chinese. The characters at the top read, "Powers are divided into four," while those at the bottom read, "The world is guided by one."
"Avatar" is derived from a Sanskrit word which literally means "those who descend."