Purple pentapus

The purple pentapus is a small, five-legged purple cephalopod that leaves red marks when the suction of its tentacles is released from the skin of the person to whom it was attached. The creature is difficult to remove with brute force once attached, but if one strokes its head, it will readily release its grip.

History
Purple pentapi were encountered by Team Avatar in the city of Omashu when Sokka climbed up a sewer pipe and came out with many of them 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 guards were fooled by the pentapi's suction marks into believing that all the people had come down with a bad case of pentapox, a disease earlier invented by Katara 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 which name is an alliteration are the canyon crawler, fire ferret, gorilla goat, pygmy puma, rabbiroo, snail sloth, spider snake, and the firefly.
 * 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 as the octopus is named after its having eight.