Shapeshifters are a popular horror movie villain trope and have been portrayed to varying success over the years. Supernatural portrays shapeshifters as humans who have learned to switch forms, taking on inhuman characteristics. Captain Marvel and the MCU use the shapeshifting Skrulls as misunderstood villains, and the X-Men universe uses the D'Bari as an evil alien race intent on finding the Dark Phoenix.
While shapeshifters are portrayed in many different ways, the most impactful are those that leave a horrific image in the audience's mind. Shapeshifting monsters in horror fiction can switch forms at will or go through a painful transformation that changes their body indefinitely.
Pennywise - It
Pennywise, also known simply as "It," is the quintessential shapeshifter, changing into whatever his prey fears the most. It mainly appears as Pennywise the Dancing Clown since, as per ScreenRant, Stephen King thought that clowns are something that children would fear the most, but It's true form is an amorphous organe light know as the Deadlights. Pennywise can also alter reality, making characters see things that aren't there.
Tim Curry played the role brilliantly in the 1990 adaptation, beating out many other actors that were considered for the role such as Malcolm McDowell. Bill Skarsgard played Pennywise in the 2017 and 2019 films, creating a truly creepy monster.
Seth Brundle - The Fly
The Fly is a science fiction-horror movie starring Jeff Goldblum as Seth, a brilliant scientist that slowly and painfully transforms into a fly-creature after testing out a teleportation device. Seth loses his mind and humanity throughout the film, becoming a true monster via his physical and mental transformation.
The film features some gory and genuinely disgusting images such as Seth losing his skin and teeth. Shapeshifting monsters in horror go hand-in-hand with gore and pain, as their transformations make the characters less than human.
The Thing - The Thing
The Thing is a parasitic alien that arrives at an American research lab in Antarctica in the form of a dog. The Thing horrifically turns its victims into monsters, sprouting extra legs and warping their faces. What makes this alien so dangerous is its ability to mimic humans perfectly, surprising its victims when it suddenly transforms.
The horrifying creature effects make this film one of John Carpenter's best, next to the atmospheric The Fog. Carpenter worked with Rob Bottin on the creature design and effects for both films, making them classics that were underappreciated in their time.
The Werewolf - An American Werewolf in London
An American Werewolf in London is a horror-comedy—not only is it gory, but it's sharp and clever, too. The main character, David, is attacked by a werewolf and cursed with lycanthropic transformation under the full moon. His friend Jack is mauled to death and returns as an undead zombie to try and prevent David from hurting anyone else.
The iconic werewolf transformation scene is disgusting and looks absolutely painful, with David's bones stretching and breaking as he slowly transforms. The sound design aids the scene, the crackling of the bones and David's howling screams getting a genuine wince from the audience.
The Entity - It Follows
It Follows is a chilling horror film that features a sexually transmitted demon that follows its victims until it kills them. The entity is capable of taking on many forms, but, even its usual humanoid form, it is terrifying as it slowly approaches the victim, creating a sense of impending doom.
The ambiguous ending of It Follows and the entity's shapeshifting also enhances the horror, as the entity could still be following the protagonists and could theoretically be anyone on the street.
The Beldam - Coraline
The Beldam, otherwise known as the Other Mother, attempts to trap Coraline and other victims in the Other World to consume their life force. The Other World is one of the bleakest fantasy worlds in fiction, trapping its victims to consume their souls. The Beldam takes on the appearance of the victims' loved ones—in this case, Coraline's mother—to convince the victims of her love and affection towards them.
As the Other World is stripped away, so is the Beldam's disguise, revealing her true form as a skeleton-thin witch. She has other powers, namely manipulation and the ability to steal and consume souls.
Freddy Krueger - A Nightmare on Elm Street
Freddy is the main antagonist of the Nightmare on Elm Street franchise, one of the few horror franchises to have more than one reboot. Freddy has the power to enter and manipulate children's dreams. When he was alive, he was a serial killer who targeted children. While he is impossible to kill in the dream world, he loses his powers in the human world.
His main shapeshifting capabilities come from his ability to transform into various frightening creatures, possess people, and disguise himself in human form when taken out of the dream world. Freddy is an iconic horror character that has appeared in numerous films in his own franchise, as well as various other properties such as Ready Player One and The Simpsons.
The Parasites - Parasyte: The Maxim
An army of alien Parasites arrives on Earth, taking over people's brains to control the human species and dominate the planet. The Parasites are deadly weapons that kill without hesitation, transforming their usually humanoid bodies into various bladed weapons. The most terrifying Parasites can morph their heads into giant mouths, chomping off human heads in the blink of an eye.
The Parasites are terrifying, as they could be anyone walking among humans normally until they get the urge to feed. The Parasites' kills are called "mincemeat murders" for their gruesome and gory fatalities.
The Shimmer - Annihilation
The Shimmer arrives on Earth and sets up a base, slowly expanding its borders and posing a threat to humanity. Any humans that enter the base, known as Area X, are slowly mutated, with the Shimmer's influence entering their bodies. The Shimmer creates doppelgangers of various soldiers that have entered Area X and is able to take humanoid form after absorbing a drop of blood from the main character Lena's face, mimicking her movements.
There is debate among the survivors at the end of the film whether the Shimmer was trying to be good or bad, but, either way, the mutant creatures that the Shimmer creates and the creepy doppelgangers more than make this alien a terrifying threat.
The Empty Child - Doctor Who
Doctor Who is not a stranger to shapeshifting aliens, since the main character is able to change his face during regeneration, and one of the most iconic enemies is the Zygons, who can shapeshift out of their usual slimy triangle forms. However, the scariest monsters are those that affect the humans around them—for instance, the Empty Child.
The Child is terrifying for his simple catchphrase, "Mummy?," as well as his ability to transform anyone who touches him into a zombie. The transformation, demonstrated on a hospital doctor, is absolutely terrifying, with the victim's bones crushing and creating a gas mask that fuses to their face.