A Cucuy is a creature that feeds on human kidneys. preferably those of children. They want to feed off the bodily chemicals that gathers in human kidneys and in children that chemical is more potent. They have the outward appearance of a normal human but their jaws grow longer and grows two sets of flesh cutting teeth when it attacks.
The only way (human) to kill a Cucuy is to take an iron blade and pierce its brain with it.
Season 9Sam and Dean ran across a Cucuy when it started feeding on children that were due for surgeries or medical procedures at a hospital. Their fear and nerves drew the Cucuy to them and it stalked them to heighten their fear before it struck. It had already fed off the kidneys of two of the children that had been there already. Dean soon found the Cucuy that had been masquerading as a nurse. Sam and Dean chased it through the hospital where it was finally slain by Gadreel who had been working there as a security guard. It tried to defend its actions to the angel but Gadreel was indifferent to its pleas before he smote it.
Facts and Lore
A cucuy is known as the latin version of the boogeyman in Mexico and Central America. It is said to be a creature that feeds off the fear of children.