Times where being possessed causes the vessel to transform in Literature.
- In the second book of Robin Jarvis' Deptford Mice trilogy, The Crystal Prison, Madame Akkikuyu unwittingly performs a ceremony that will bring the Big Bad, the evil cat Jupiter, back from the dead. However, as his old body was destroyed by fire, he will need a new one. Thus he awards Akkikuyu with "the highest honour that is [his] to give"... she will be the new host for his spirit. In preparation for this, she begins to transform into a cat, much to her horror. However, before Jupiter can fully take possession of her body, she kills herself by jumping onto a bonfire.
- True for most Denarians in The Dresden Files, though some of them choose to keep their human appearance.
- Professor Quirell from Harry Potter and the Philosopher's Stone. As he's the willing host of Voldemort, the latter's face appears at the back of Quirell's head. Quirell wears a turban at all times precisely because of that, so he can conceal his master's existence. Unlike most other examples on this page, Quirell actually retains his mind, and works for Voldemort, as opposed to Voldemort directly controlling his body.
- The Big Bad of Heralds of Valdemar is a long-dead sorcerer, first known as Ma'ar, who's utilized the bodies of his descendants for thousands of years. Usually the bodies he takes are in their early teens, and rather than suffering puberty he magically forces it to grow up quickly. He also remodels each body, starting with his own when he was alive, to his whims, usually making it beautiful. As Krebain he gave himself clawed fingers and such striking good looks that Vanyel, used to Beauty Equals Goodness, compares it to makeup. In his next life as Leareth he makes himself into Vanyel's Palette Swap. Centuries later, as Falconsbane, he gave himself extensive lynxlike features including Animal Eyes, which he first tested on Nyara.
- As Falconsbane his host's spirit, for once, was not destroyed by possession. Through major heroic effort Falconsbane was exorcised and his host An'desha could reclaim his body - still a towering, taloned, lynx-man. Fortunately for An'desha, a pair of friendly Avatars soon reverted his body to young and in (mostly) the same shape it had been when the spirit possessed him.
- In Inheritance Cycle, when a human is possessed by spirits and becomes a Shade, it transforms their appearance, including turning their hair bright crimson.
- Gods in The Kane Chronicles need a human or animal host to exist on Earth but can shapeshift it to look like anything they want. For example, Bast can change her cat host into a human.
- The Locked Tomb: When spirits invade Colum's temporarily soulless body in Gideon the Ninth, its eyes become tooth-ringed voids from which long grey tongues protrude. The possessors also do an Exorcist Head twist to get a closer look at someone.
- In Night's Dawn, possessors can reshape their hosts' bodies, but shouldn't because it's carcinogenic.
- Old Kingdom: Dead spirits mutate the corpses they're summoned into, although their original occupants are (usually) mercifully absent by then. This is at least partially intentional: the newly animated Dead Hands in Goldenhand customize their bodies with claws, fangs, and an Abnormal Limb Rotation Range as they pursue some humans.
- Played with in Perelandra, Dr. Weston's possessed body at first looks quite normal but as it is damaged beyond repair in the course of the plot (yet continues to move thanks to the devil inside it), it becomes horrible to look at and wholly inhuman.
- Rivers of London: Punch uses a spell to reshape the face of the person he's possessing into his own face, shattering bone and damaging tissue in the process. The spell holds it together while it's active, but as soon as the spell ends, the person's face falls apart, with usually fatal consequences.
- Spellbent: Possession victims get funky eye colors. Their sclera (white of the eyes) turns red or in some cases purple, depending on the power level of what's possessing them.
- In The Stormlight Archive, the Listeners (a.k.a. the Parshendi) can shift between a number of different physical forms by bonding to different spirits. The closest example of this trope comes in stormform, which they gain by binding a spirit of Cosmic Hatred and which comes with a large helping of This Is Your Brain on Evil.
- Downplayed with the body surfing Fused; when a Fused's spirit inhabits a new body, it doesn't completely change, but will manifest enough of that Fused's distinctive features that people who are familiar with them can recognize them across multiple incarnations.
- Witch King: Demons in human bodies always gain monochromatic black eyes. When the demon protagonist needs to avoid attention, he wears a veil, a low hood, or, on one memorable occasion, decoy eyeballs.
- Yumi and the Nightmare Painter: Zig-zagged and justified while Yumi and Painter are taking turns in each other's bodies. Yumi's body doesn't change while Painter is inhabiting it, but Yumi's vast Soul Power transforms Painter's body to match her Residual Self-Image while she's inside it.
