I've always loved the way shapeshifter stories make the internal struggle so physical. It's not just a character wondering 'who am I?' They're literally wrestling with another form, a whole different set of instincts. That moment when a character has to decide whether to give in to the animal's urges or fight for their human self? That's identity crisis on steroids. The transformation scene is rarely just about cool special effects; it's painful, messy, and deeply personal. I remember reading a werewolf story where the protagonist dreaded the full moon not because they'd become a monster, but because they loved the raw freedom of it, and that scared them more. That conflict between what society says you should be and what you feel you are—it's all right there in the claws and the teeth.
Some books use it as a metaphor for puberty or coming into your own power, which is pretty obvious but still works. Others get into more complex stuff like dual consciousness or losing yourself entirely to the beast. The best ones don't let the human side 'win' completely; there's always a negotiation, a new hybrid identity that emerges. It's never clean.