Shape-shifting is a common theme in mythology, folklore, and fairy tales. In its broadest sense, shape-shifting occurs when a being (usually human) either (1) has the ability to change its shape into that of another person, creature, or other entity or (2) finds its shape involuntarily changed by someone else. If the shape change is voluntary, its cause may be an act of will, a magic word or magic words, a potion, or a magic object. If the change...