Hermit crab

The Hermit Crabs have a shell-switching lifestyle, and they are covered in a thick coat of black and white hair. They seem to prefer damp, dark places and are apparently very adaptable, as specimens in the Northern Air Temple survived a complete refurbishment of the entire complex, spearheaded by the the Mechanist. It seems fitting and is perhaps not coincidental that a nomadic animal by nature would live among the Air Nomads. This animals change of shell from time to time, and Aang compared this with the people was living in the Northern Air Temple, saying: "Maybe you weren't born here, but you found this empty shell and made it your home".

Connection
The hermit crabs look quite similar to the aquatic crabs in the real world.