The winged lemur is a small, energetic animal that is critically endangered. Momo is the only known descendant of winged lemurs that survived the Air Nomad Genocide, though the ring-tailed winged lemur, a closely related species, was discovered after the end of the Hundred Year War.
Prior to the Hundred Year War, many winged lemurs lived at the air temples. While relaxing one day at the Southern Air Temple, Aang and Gyatso flung some fruit pies at a few elder monks, and several winged lemurs took the opportunity to eat the splattered remains of the food.
After the Air Nomad Genocide, the winged lemurs were almost wiped out. Upon returning to the Southern Air Temple, Aang found and befriended the only known living lemur and named him Momo. From that point onward, the lemur was a companion to Team Avatar and followed the group on their adventures.
The winged lemur is equipped with large membrane-like wings attached to its arms that allow it to take flight. It has a prominently black face with two proportionately large, green eyes, and its fur is mostly white with several black stripes. Other color markings and variations have been seen. The winged lemur has two very wide, long ears on its head that give it fantastic hearing. It has a monkey-like tail, which is usually black with two white stripes at its tip. It is also very quick and agile. The lemur seems to have a very acute sense of smell, as it is able to detect food at a moderate distance.
The lemurs were extremely popular with Air Nomad children and adults alike; they were the Air Nomad children's favorite pets. The airbenders trained them to do many tasks, one of which was to retrieve the gliders if the nomads dropped them from their flying bison. Winged lemurs love food, and are not above taking it directly out of the hands of any person who might be holding it at the time. They like to be petted like dogs or cats. When a winged lemur is frightened or is threatening an enemy, it raises its back and hisses, much like a common house cat.
Real world lemurs are similar in appearance to the winged lemur, with regards to body shape, color, and face. The coloration of their fur favors that of a sifaka, a species of lemur in the real world which is also critically endangered. The other half of the winged lemur's body structure resembles that of a spotted bat; its wings are similar to a bat's as well. Furthermore, the lemur resembles the common house cat in terms of its demeanor, curiosity, and reactions. Winged lemurs also share a few similarities with colugos, referred to as the "flying lemurs" of the real world.
- Although Momo was believed to be the only known living lemur, Tho claimed to have seen a lemur in a traveling circus.
- The winged lemurs have their own theme song; while it is normally fast and lively, the music is played in a slow, relaxed way while Momo is gorging himself.