In the Irish tradition, the Pooka or Puca is mischievous spirits in a half-human form that can transform at will. Pookas punish grave robbing and ingratitude and have been known to rescue beasts found in bogs. Pooka sometimes help in the household tasks and tidies up after people. Irish children call snails Pookas and bid them put out their horns in a nursery rhyme. Before Halloween, it’s safe to eat the wayside blackberry but after Halloween, it’s not due the Pookas smites the fruit, making it inedible by dirtying it.
John and Caitlin Matthews, The Element Encyclopaedia of Magical Creatures, 2013, Pooka, p 375