A puca (also pooka) is in Irish folklore, a spirit that is both helpful and mischievous. The puca has the helpful characteristics of the household BROWNIE and the mischievous characteristics of the Bogey and the bucca. The puca is a shape-shifter and is often seen in the form of a black animal or a black half-animal. When he is so inclined, he favours humans by enabling them to understand animal speech and by protecting them from evil spirits. If treated well, household pucas will clean up the house during the night and also do yard work. Ungrateful people invoke the puca’s wrath. He also bedevils grave robbers. In English folklore the puca is known as puck, a household spirit who in medieval times was viewed as having a particularly malicious nature and was often identified with the Devil. Puck is also known as Robin Goodfellow, described in 16th-century literature as the child of a human girl and a fairy.
Robin Goodfellow has the ability to shape-shift into animals and enjoys playing tricks on humans. He also performs household chores in return for milk or cream and bread or cake.
The Encyclopedia of Ghosts and Spirits – Written by Rosemary Ellen Guiley – September 1, 2007