A little of both. Depictions of leprechauns in the Irish oral tradition have been varied, but most accounts had them as humanoid figures, about the size of a mouse, with big feet—a cute creature, to be sure, but also a tricky one that could turn deadly if not treated with proper respect. Some of a leprechaun's tricks would be more annoying than dangerous. He might show you the location of a buried pot of gold by tying a ribbon around a tree, for example, but when you came back the next day, he’d have put ribbons around all the trees to prevent you from finding it. Or maybe he'd grant you three wishes, and then he’d trick you into making a fourth wish, thereby undoing the first three. But in other stories, a leprechaun might kidnap you, replace your infant with a changeling, or even kill you if you came too near his treasure.