Appa

Appa is a flying Bison from Avatar the Last Airbender. He is under the ownership of Aang as well as his animal guide.

Ultimate Story
Appa made his first appearance in Ultimate Story 3. He was team Avatar's main form of transportation. He was used by the team to escape the chaos that was occurring.

In Ultimate Story 4, he was brought out of the Avatar's world as a summon. He can be summoned by Aang, Katara and Sokka.

Within the US4 spinoff, Powerful Harmony, Appa had been summoned many times as one of the group's main form of transportation. Aang summoned Appa for a brief moment to show his new friends, Ahsoka, Anakin, Obi-wan and Padme, as well as prove that there was such a thing as a flying bison to Anakin.

During the story, Aang had taught Ahsoka how to fly Appa. She really loved and adored Appa and enjoyed learning how to fly him. She then taught her master, Anakin, how to fly him and then Obi-wan learned how to fly him, too.