Appa

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.

Early life
When Appa was still a young calf who lived around the Eastern Air Temple, young airbenders were allowed to meet their future companions, who would bond with them for life. The herd's mother willingly directed her calves to meet the young monks. Aang came forward and offered an apple to Appa, and the two became best friends almost immediately afterward.

Just before the Air Nomad Genocide, Aang heard that the monks were going to separate him from Monk Gyatso and subsequently decided to run away, using Appa as his mode of departure. Appa didn't know where he was going, only that he was leaving the air temples.

Journey to the North
Aang flew Appa over the ocean, at which point they were caught in a vicious storm which pushed the two underwater by stirring up the wind and the waves until Aang lost consciousness. Faced with a life-or-death situation, the young Avatar entered the Avatar State and froze himself with Appa in an iceberg, the latter was stuck in hibernation along with Aang for one hundred years.

The pair were discovered by Katara and Sokka. After this, Appa became the group's main form of transportation in their quest to help Aang master all four elements through the world. He appeared in most of Sokka and Princess Yue's dates, tried to steal food with Momo in the Foggy Swamp, and became a beloved friend for all members of Team Avatar.

Disappearance
Appa became lost for a short while when the group was traveling through the Earth Kingdom, having been kidnapped by a group of sandbenders in the middle of the vast Si Wong Desert, while Aang, Katara, Sokka, and Momo were trapped in an underground Spirit library.

It was later revealed that Appa was eventually sold to beetle-headed merchants, who in turn sold him to a Fire Nation circus where a sadistic trainer attempted to make him part of the show. Encouraged by a sympathetic boy, he later escaped and hurried back to the Si Wong Desert where he last saw Aang. Understanding that his friends weren't there anymore, Appa journeyed throughout the Earth Kingdom until he encountered the Kyoshi Warriors, who healed his various wounds, physical as well as emotional, that he had sustained on his travels. They wanted to escort him back to Aang, but they were soon thwarted in their attempt when Azula and her allies attacked. He was forced to flee, ushered away by Sukiwhile the warriors tried to delay the three Fire Nation girls.

On his journey Appa encountered Guru Pathik at the Eastern Air Temple, where the Guru was able to tell Appa of Aang's location by reading his energy. Consequently, he flew to Ba Sing Se, where he was captured by Long Feng and kept in a secret location under Lake Laogai until his rescue at the hands of Zuko, who was initially planning on utilizing him to capture the Avatar until he talked with his uncle Iroh, deciding to do the right thing and set the bison free.

Earth Kingdom
Appa found the group cornered by Long Feng and the Dai Li and was instrumental in their defeat, biting Long Feng on the leg when confronted by him. Once safe, Aang welcomed him in a tearful display of affection. Appa took part in forcibly entering the Royal Palace of Ba Sing Se, providing the first piece of evidence to King Kuei of Long Feng's subterfuge since Long Feng's bite mark still lingered.

When the Dai Li's cover up efforts left the Earth King skeptical of Team Avatar's claims, Sokka made a last-ditch effort to show the king the ruined Fire Nation drill by enticing him with a ride on Appa. Since his saddle was lost during his capture, the group was forced to ride bareback. After the fall of Ba Sing Se, Appa was seen spiriting Team Avatar, including a near-fatally wounded Aang, the Earth King, and his pet, Bosco, out of the now-captured city.

In the Fire Nation
Appa stayed with the group as they found their way aboard Hakoda's commandeered Fire Navy vessel and had a new saddle constructed for him. After Aang ran off into a storm, Appa and the rest of Team Avatar split with Hakoda's crew and chased down Aang, regrouping on Crescent Island. As they traveled through the Fire Nation, Appa was forced to stay hidden until he did have to fly, while Aang and Katara created a cloud around him so that he resembled a cloud to any Fire Nation civilians. When they left him and Momo alone, the gang had to cover Appa up with some form of camouflage.

After the invasion of the Fire Nation failed on the Day of Black Sun, Appa took Aang's friends and all of the younger members of the invasion force to the Western Air Temple in search of refuge. Unbeknownst to Team Avatar, Zuko abandoned the Fire Nation during the invasion and followed them to the temple. When he arrived, Appa immediately welcomed and licked him, a direct result of him remaining grateful to the prjnce for freeing him from his imprisonment in Ba Sing Se. Despite Appa's obvious welcoming of Zuko, the group didn't accept the latter's proposal of teaching Aang firebending until he saved the group from an attack conducted by Combustion Man.

In the final days of the Hundred Year War, Sozin's Comet's arrival, Appa helped Team Avatar, excluding Aang, travel to the Earth Kingdom, where they had June and her shirshu, Nyla, try to track Aang. Unsuccessful, they instead tracked down Iroh, using his sandal, who was residing outside Ba Sing Se with the rest of the Order of the White Lotus. Appa later escorted Zuko and Katara to the Fire Nation Capital for their confrontation with Azula.

After the Hundred Year War
After the Hundred Year War's end, Appa was seen in Ba Sing Se with the gang as they celebrated their victory at the Jasmine Dragon, seemingly enjoying Iroh's tsungi horn music. After this, the team decided to take a ride on Appa before Earth King Kuei's celebration in announcement of the Harmony Restoration Movement to the kingdom.

A year later, when the movement was being carried out, Appa helped Team Avatar transport Fire Nation colonials back to their nation.

One year following the failure of the Harmony Restoration Movement, Appa once again embarked on a mission and transported Team Avatar to Hira'a in search of Zuko's mother, Ursa. However, he was visibly upset that Azula would be accompanying the team on the trip. On their way there, the party was attacked by a wolf spirit, so Appa aided in the battle against the beast. Once the team learned about Ikem's flight up Forgetful Valley, he stayed behind and later flew back to Hira'a along with the remaining members of Team Avatar and the Mother of Faces.

Eventually, Appa and Aang were together for most of their lives up until the latter's death.

Personality
Appa seemed to have a reasonably trusting attitude, as he didn't take long to accept the apple offered to him by Aang - to whom he became incredibly loyal and took an immediate liking to Sokka when he first saw him. However, this trait was damaged due to his experience with the circus trainer and the sandbenders. In these difficult moments, he seemed to have similar feelings toward humans when he missed Aang and his family in the Eastern Temple while he tried his best to find Team Avatar.

Appa might have had some degree of intelligence, yawning after Aang prompted him  and apparently "scolded" Hawky and Momo when the two fought due to Sokka's order that himself was in charge. His intelligence was further shown when he was taking the team and Professor Zei to Wan Shi Tong's library, responding with a groan when Zei asked him a question.

Appa was afraid of going underground. Since his experience in the Fire Nation circus, he also developed a fear towards fire.

Airbending
Being a sky bison, Appa possessed airbending and apparently used his tail as the main driving force behind his bending, but he also had shown the ability to accomplish it with his mouth. He mainly used his ability to fly at extreme heights and avoid attacks. Despite the tranquility related to his personality and species, Appa had shown himself to be capable of fighting whenever necessary, creating powerful gusts of air with just a flick of his tail and gaining an advantage over his opponents by hovering. He even defeated Long Feng, Ty Lee, and Mai.

Strength
Being a bison, Appa had a great deal of brute strength and endurance. The best demonstrations of this were in the fight against Nyla in the abbey, and against a fully-grown boar-q-pine in the forest. His strength was so great to the extent of Appa lifting two Fire Nation tundra tanks simultaneously each by the horn, flipping them over. Using his teeth alone, he was capable of grabbing Long Feng by his leg and throwing him a great distance.

Stamina
Due to his size and mass, it took a lot of energy for Appa to stay aloft, so he couldn't fly for an extended time and periodically required stopping or resting. However, there were times when he displayed extreme stamina, such as when Katara stated that they flew two days non-stop and when he continually had to fly in order to avoid Azula, Ty Lee, and Mai for hours on end with only a few minutes of rest each time he stopped. Furthermore, Appa was capable of carrying quite a burden on his back, having once carried seven medium-weight people in one journey.

Other Skills
Appa was capable of swimming, even being a fairly adept. However, he would more frequently fly or walk rather than swim.

Although lacking the ability to speak human language, Appa does understand human language.

Trivia

 * Appa was originally a dog-like animal and much smaller, albeit still larger than Aang. The design was eventually recycled into Naga, Korra's animal companion.
 * Co-creator Bryan Konietzko described Appa as a manatee-bison hybrid, although the manatee aspect of Appa is extremely subtle. Early development sketches of Appa show him with much more manatee-like facial features.
 * Early designs also show Appa with spiral horns, however they were removed due to being "too difficult to animate by hand".


 * Appa's design is similar to that of the Catbus from the anime film My Neighbor Totoro which was made in 1988. The Catbus also has multiple legs and a large tail.
 * Appa's name is a palindrome, like Kuruk and Ikki.
 * In Avatar Extras for "The Library", it was stated that Appa had a double-chin.
 * According to his missing posters and a statement made by Aang, Appa's weight was ten tons. In "The Warriors of Kyoshi", Sokka referred to Appa as a "ten-ton magical monster".
 * Although Aang is said to be the last airbender in the series, Appa was an airbender. This means more specifically that Aang was the last human airbender and more so the last Air Nomad.
 * Appa wouldn't respond to the bison whistle if he was napping.
 * As indicated by his flat teeth and diet, which was mainly composed of plants and fruits, Appa was a herbivore. Like most farm animals, he seemed to prefer hay when it was available, though he also consumed honey and attempted to snatch an egg when he was desperate for food.
 * It was shown that Appa could sleep on his side with his legs wrapped around his tail.