The head is one of the most important parts of the body. It contains the brain, eyes, ears, nose, and mouth; all vital organs for perception and aid in various sensory functions such as sight, hearing, smell, and taste, respectively. Now imagine if in its place is a different body part... yet it retains some or all the features and functions of a regular head. That would be this trope.
Cephalization or development of heads in animals is an evolutionary trend to concentrate the nervous system, sense organs, and feeding structures at a front end, but the evolutionary process for the creatures with this trope either didn't see it fit to do so or just took an effort to be as weird as possible.
Animate Body Parts have a chance of becoming this if they gain a completely separate body but they may also go for being a Cephalothorax (so you can have another body part functioning as a head that is also a chest). Specifically, a creature with an eye as its entire "head-chest" is also an Oculothorax and those examples should go there.
For the trope to be played straight, the replacement organ must still serve its intended purpose in addition to being a head. A head that merely looks like another body part (like in the cases of some Eldritch Abominations, Starfish Aliens, and Gonks) is a subversion.
With or without actual facial features, this may lead to Nightmare Face if the body part in place of the head just feels wrong. It may overlap with Multiple Head Case, if other body parts are also functioning as heads by their own right, and other Spare Body Parts tropes, if a part replacing the head creates a surplus.
- The Neozep brand of cold medicine from the Philippines has the "Ilong (Filipino for "nose") Ranger" as its Mascot.
- This Alka-Seltzer commercial from 1967 has a stomach, played by Gene Wilder, as a Cephalothorax.
- These Coke Zero commercials have two tongues, an eye, and a finger with non-human legs. On the other hand, the armed brain on a skateboard is a Brain Monster.
- Spy Kids: The genetically engineered "Thumb-Thumbs" made by Floop are gigantic humanoid monsters with their arms, legs, and head all giant thumbs.
- The Nikolai Gogol story "The Nose" has a detached nose that was able to pass itself off as a human being with its own body and surpass the rank of its owner.
- Zigzagged in Ringworld, where Pierson's Puppeteers have their brains in their thoracic cavities. Their two heads, resembling hands with Extra Digits, play no role in thinking, instead being used mainly for eating and manipulating objects.
- The Bum Trilogy: The first book has people's butts planning to invoke this by taking over the world with a huge, worldwide fart by building up a massive quantity of methane gas in the "Bumcano." When the Bumcano blows, all humans will be rendered unconscious, then the bums will seize their chance and switch places with their heads.
- An episode of Saturday Night Live (hosted by Jon Stewart) had a sketch where he plays the founder of several boy bands and presents his latest such group, which he genetically engineered himself. It's also revealed that he contaminated one batch and the resulting members came out wrong. One of these members, Ass-Face, has... well, look at his name and guess.
- Pokémon: Binacle, introduced in Gen VI, looks like a pair of arms with faces on them stuck on a rock. Its evolution, Barbaracle, have those two Binacle multiply into seven and rearranged into a humanoid form (one in the middle as the head and thorax, four as limbs, and two as Vertical Mecha Fins). All of them have a mind of their own, but they usually follow the one in the middle. These designs are also invoked by the Japanese word for barnacle, kamenote, which means "turtle's hand."
- Yo Kai Watch:
- Cuttincheez/Hekokijin and Cheeksqueek/Onarazumono have butts for heads and they can fart with it. Yup.
- The Bananose/Nagabanana line, and others with similar name and appearance, may be Yokai with exaggerated Gag Noses or their heads are giant noses with facial features. Or they're anthropomorphic bananas.
- Undertale: One of the receptionists in MTT Resort has a giant hand for a head.
- In Alex Kidd in Miracle World, Stone-Head, Paper-Head, and Scissors-Head have hands making their respective RockPaperScissors gestures for heads.
- Shin Megami Tensei: Prepare the Brain Bleach.
- Though Atlus wouldn't admit that it's intended, it has several phallic examples in Mara, Ym, and, Mishaguji (who is depicted to be either snake-like or humanoid depending on the specific installment). DO NOT spare a thought if these function as intended but the designs are justified for these demons/deities associated with either temptation, fertility, or both in their original myths. Ym is also a deity of agriculture so his head must be meant to represent root crops (yam, geddit?)... but who are we kidding?
- Catherine: Zigzagged with the Immoral Beast. It's a creature that crawls on its four weirdly angled limbs like a crab and has its conjoined buttocks as its head. It has an eye on each cheek, while the rest of its deformed facial features are on its "upper back," and a "mouth" with an Overly Long Tongue sticking out. It is a manifestation of Vincent's guilt from having an affair.
- Dark Souls III has the Monstrosity of Sin, which has a massive hand-like head and its palm has a gaping hole lined with teeth.
- Wander over Yonder: While Lord Hater leads the Army of Watchdogs, who have eyeballs as their entire headsnote , Emperor Awesome has the Fist Fighters, who are humanoids with fists for heads. The Knucklehead variant works as a Bouncer for his parties.
- Gravity Falls
- The Shape Shifter from "Into the Bunker" transformed into a creature with a fist for a head, with one eye and mouth in its "palms."
- Mabel summoned a centaur-taur in "Dungeons, Dungeons, & More Dungeons." It is a horse whose head... is an entire horse's body. It's basically the result of putting two headless horses together.
- "Teeth," from Bill Cipher's invasion posse, is a gummed set of teeth with limbs who wouldn't look out of place as a mascot in oral hygiene commercials.
- Future-Worm!: Taking this trope to the Logical Extreme and overlapping with Anthropomorphic Food, Steak Starbolt is a sentient piece of steak, a sliced flesh, with a humanoid body.
- In Pickle and Peanut, Pickle dates a girl with a foot face.
- The Earclops/Earclopes/Earclopses in Adventure Time are large, humanoid beings with ears as heads. Due to their giant ears, they are very sensitive to loud noises.
- The Day My Butt Went Psycho!, loosely based on The Bum Trilogy and named after the first book, has butts with lives and humanoid bodies separate from the people they're supposed to be attached to.