Purple pentapus

The purple pentapus is a small, five-legged cephalopod which leaves red marks when its tentacles are detached from a person's skin. The creature is difficult to remove with brute force once attached, but if one strokes its head, a gesture which pentapuses immensely appreciate, it will readily release its grip.

History
Team Avatar encountered this species in the city of Omashu while navigating through a sewer pipe. When Sokka crawled out of the sewer pipe, he had several pentapi clinging to his face. The distinctive suction marks left by these animals were later used by Sokka as a way to lead the citizens of Omashu outside the captured city's gates. The pentapi's suction marks fooled the guards into believing that all the inhabitants were infected with pentapox, a disease Katara had made up earlier in order to conceal their identity from the guards.

Anatomy
The purple pentapus is a five-eyed, five-tentacled, octopus-like creature that lives in the sewers of Omashu and is roughly the size of a human fist. Using the small suction cups on its tentacles, it latches onto targets, though it is apparently harmless. In fact, its tentacles are used to grip the sides of sewers in order to eat algae and other food.

Connection
The purple pentapus resembles an octopus but on a much smaller scale. Unlike the octopus, the small invertebrate has only five arms, like a starfish.

Trivia

 * The purple pentapus' name is the strongest example of alliteration in the series by repeating the consonant 'p' four times. Other creatures in the series whose names are alliterations are the canyon crawler, fire ferret, flying fishopotamus, goat gorilla, pygmy puma, snail sloth, and spider snake.
 * Penta (πέντε) is a Greek numerical prefix for "five", and pus is derived from the Greek pous (πούς), which means "leg". The name thus refers to the five limbs of the animal, much like how the octopus' name comes from it having eight limbs.
 * In the video game The Burning Earth, the pluralization of "pentapus" was noted to be "pentapii", versus the more conventional pluralization of "pentapuses".