The cucuy is a Latin magical creature. Like werewolves and angels, cucuys look human most of the time, but they can change their appearance.
In this case, they can change their face to a dark-gray skull shape, with large red eyes. In Alex Gives Up, Lisa Cucuy begins to like Max Russo. Then she meets Mason Greyback, Alex Russo's boyfriend, showing that most likely Lisa cheats on boys. It is also known that Theresa Russo, Max and Alex's mother, likes to keep her distance from cucuys.