Wood frog

Wood frogs are palm-sized, brown-colored amphibians who dwell within Earth Kingdom swamps. During the winter, these frogs hibernate by freezing themselves and sitting at the bottom of the river bed. While frozen, their skin secretes a substance that has medicinal purposes, which disappears directly after they thaw.

History
When Katara and Sokka fell ill, Aang went to the Herbalist and asked for help. The Herbalist told Aang to seek out the wood frog. The ones Aang had collected before the Yu Yan Archers had captured him thawed and hopped out of the room in which Aang was held in, confusing the guards. Afterwards, Aang found the creatures and, placing them into Sokka and Katara's mouths, told them to suck on them until the illness wore off. Sokka, while still feverish, claimed that the substance was "tasty," but he and Katara spit the wood frogs out after they thawed and began to wriggle. Sokka and Katara then started to cough and gag. It took weeks for them to get the frog taste out of their mouths. Sokka later claimed to have a wart on his uvula, or "throatal-flap," for a month afterward, though Katara disagreed.

Connection
The wood frog is based on the real world wood frog that can actually survive while frozen solid.

Trivia

 * The wood frog is one of very few nonchimerical (unhybridized) animals seen in the [Earth|world of Avatar]]. Other examples include Miyuki, an unhybridized cat, and Bosco, the Earth King's bear.