The name of the sea serpent, Unagi, is the Japanese word for eel.
The design of the Kyoshi Warriors is heavily influenced by Japanese culture. There is a Japanese symbol pressed onto a gold feature of their sleeves, Kyo, meaning "capital." Their makeup is also inspired by Keisha and Kabuki makeup.
The fans the Kyoshi Warriors use are based on the tessen, a metal Japanese war fan.
Some of the food Aang and Katara are seen eating resembles Japanese desserts, such as doryaki, nori maki, and monaka.
In Zuko's bedroom, ancient Chinese weapons called deerhorn knives are visible.