Aang was an Air Nomad born in 12 BG and the Avatar during the Hundred Year War, succeeding Avatar Roku and preceding Avatar Korra. As the Avatar of his time, he was the only person capable of using all four bending arts: airbending, waterbending, earthbending, and firebending. He was also one of a select few Avatars and one of the first in many cycles to learn the ancient art of energybending as well as the first Avatar known to have actively used the technique.

Shortly before the beginning of the Hundred Year War, Aang was frozen in an iceberg for a hundred years; he later emerged, still biologically twelve years old, into a world engulfed by war. During his absence, the Fire Nation had waged war upon the other nations and managed to completely wipe out the pacifistic Air Nomads. It fell to Aang, the Avatar and the last airbender, to end the War by mastering the other three elements and defeating Fire Lord Ozai. He remained a kind and goofy kid at heart throughout his year-long struggle, despite the overwhelming loss of his people and the heavy burdens he was forced to bear. After his victory over the Phoenix King, Aang began a romantic relationship with his close friend, Katara. The couple eventually married and raised a family of three children: Bumi, the oldest, a nonbender who became an airbender later in life; Kya, a waterbender; and the youngest, Tenzin, an airbender.

Appa was Avatar Aang's loyal sky bison, who shared a strong bond with him and Momo as they were all some of the few remaining traces of the Air Nomad civilization. Appa was most noted for his ability to fly in spite of his heavy weight, a feat achieved through airbending, which made him the primary means of transportation utilized by Team Avatar.

Momo was a winged lemur and a loyal companion of Avatar Aang and his friends. By late 99 AG, he lived at the Southern Air Temple and was the only known specimen of the winged lemur species to still be alive after the Air Nomad Genocide.