The proliferation of shape-shifters in all periods and genres of literature, from Ovid's Metamorphoses to Robert Louis Stevenson's Dr. Jekyll and Mr. Hyde, testifies to our ongoing fascination with such figures and narratives. Shape-shifting is particularly prevalent in fantasy literature, especially in children's or youths' fantasy literature, where it is frequently connected to the themes of identity and the development of the hero. For example, in two of the most studied youth's fantasy literature texts, A Wizard of Earthsea and The Sword in the Stone, Ursula K. LeGuin and T. H. White link shape-shifting to the identity and development of their protagonists, Ged and the Wart (Arthur). In their texts, LeGuin and White present two traditional concepts of identity: one mutable, one fixed. The fixed notion of identity portrayed by White perpetuates an understanding of identity based upon binaries such as the mind versus the body, and resists the Aristotelian notion of "real" change, "the replacement of one existing substance by another" (Walker Bynum 177). Thus, throughout his shape-shifting, the Wart's inner, human essence perdures. LeGuin's interpretation of identity allows fluid movement between different physical forms; indeed, it even allows the simultaneous existence of two separate physical forms, Ged and his shadow. However, the notion that a single, inner essence perdures underlies LeGuin's concept of identity. Ged's raptor form flees danger and returns to Ogion's home because like Ged's shadow it shares in the consciousness of the character it signifies.
In 1999, J. K. Rowling's Harry Potter and the Prisoner of Azkaban foregrounded theriomorphic (human to animal) shape-shifting through its focus on Animagi and its werewolf figure, 'Remus Lupin.' Rowling's use of the motif and its connected themes of identity and the development of the hero places her within the tradition epitomized by White and LeGuin. In Prisoner of Azkaban, the Animagi James Potter, Sirius Black, and Peter Pettigrew all remain essentially human despite physical transformation, echoing the shape-shifting of White's Wart and LeGuin's Ged. However, unlike her predecessors, who suggest that an inner, human identity perdures, Rowling presents contradictory and sometimes irreconcilable notions of identity. While the shape-shifting of the Animagi suggests that an inner, human essence perdures, Remus Lupin's transformation suggests that "real" change can occur. Unlike the others, Lupin does not retain an inner, human consciousness when he transforms, and becomes less "wolfish" (Azkaban 260) only when surrounded by his Animagi friends. Lupin's character perdures only in its rhythmic division; that is, its transformation at each full moon. In addition, while LeGuin's Ged and his shadow exist simultaneously as the physical and psychological elements of a single being, Lupin cannot exist in both his human and wolf forms at the same time. Thus, Rowling insists, unlike White and LeGuin, that an individual can have two separate identities and that, while movement between these identities is possible, they cannot coexist. Rowling departs from traditional representations of the werewolf, shape-shifting, and identity, and instead presents a problematic interpretation of identity that reflects the cultural context within which she works.