Appa (Earth-1529)

"I guess this means we'll always be together."

- - Aang to Appa

Appa is Avatar Aang's loyal flying bison, whom he shared a strong bond, as well as Momo, remaining as one of the few traces of the Air Nomad civilization. As a flying bison, Appa was able to fly in spite of his massive weight, which he accomplished through airbending. He served as the primary means of transportation for Team Avatar and later Team Kakashi.

Early life
Appa met Aang at the Eastern Air Temple when he was still a young calf. As per Air Nomad customs, young monks-in-training had to meet and chose their future companions, whom they would bond for the rest of their lives. The mother of the herd directed her calves to meet the young monks.

Aang quickly went forward, offering an apple for Appa, and the two instantly became best friends.