Changeling Tale

Before fairies went around granting wishes and bestowing Pimped Out Dresses to cinder maids, they spent a lot of time doing some serious mischief.

One favorite game of The Fair Folk was to snatch children, and replace them with a Doppelganger, or changeling. The human baby, in turn, was taken back to the Land of Faerie. According to most European Fairy Tales, boy babies and children with Hair of Gold were in particular danger of being stolen by elves and possibly replaced by an unwanted child. Alternatively, the mother might be abducted, seduced, and impregnated by the Tuatha de Danaan (or local equivalent), resulting in a (possibly malevolent) fairy child. We know for a fact that Adultery was of course not to blame in any of these incidents. Compare Alien Abduction.

To deter fey folk, infant boys were often dressed as girls, and cold iron would be hung over cribs and doorways. Common items included horseshoes, bells, nails, scissors and steel files. What Could Possibly Go Wrong?

Simple abduction by fairytale beings also counts under this trope. Due to the inscrutable nature of the Fair Folk returns policy, 1 : 1 replacement of your kids is not warranted.

The earliest fairy tale versions are Older Than Print. Contrast Moses in the Bulrushes and Foundling Tale, where it's the parents doing the switching. See also Foundling. Compare Persephone, Year Outside, Hour Inside, and its inverse Year Inside, Hour Outside.

Subtrope of Doppelganger, The Fair Folk, Land of Faerie, Invasion of the Baby Snatchers, and very often Switched At Birth. Not to be confused with the Lighter and Softer Changeling Fantasy, which is a Rags to Riches / Cinderella Situation.

For the film, see Changeling, not to be confused with The Changeling. For the tabletop games, see Changeling: The Lost and Changeling: The Dreaming.

Anime and Manga

 * In Berserk, a young girl named Rosine offers up her parents' lives to the Godhand to become a fairy (or rather, a demon that takes the shape of a fairy). She then makes the same offer to other children, transforming them into insectile pseudodemons that can look like fairies (to the disgust of Puck, an actual elf). Her mistake is trying to make the offer to her former best friend, Jill, because said friend happens to have just met Guts.

Comics

 * In the Hellboy short story "The Corpse", Hellboy exposes a fairy changeling, then he has to perform a task for the fairies to get the original child back.
 * In Suburban Glamour (pun intended) the teenage protagonist learns that she's a literal changeling, and is the daughter of Fae royalty. She's initially elated to have the chance to get out of her dull, miserable life in a small middle-of-nowhere English village, but soon comes to realize that her Fae family are controlling and distant, and that they did abandon her for seventeen years without any explanation and as such have no right to barge into her life and start making demands of her. She decides to remain with her human parents, who at least love and respect her even if they don't always understand her.
 * In Courtney Crumrin and the Night Things, Courtney encounters a genuine changeling, but decides the baby's parents deserve it and the kid is better off among the Night Things (a.k.a. fairies).

Film

 * Changeling (2008) is a modern version of the same ancient fear, with The Fair Folk replaced by society as the antagonist.
 * Pan's Labyrinth. Although Ofelia rather loves her human mother, and seems to have loved her long-dead father, it's presented as an unambiguously better thing to live in the underworld full of magic. Mostly because dad is dead, mom is very weak-willed, and new stepdad is a zealous fascist. Unlike most examples, Guillermo del Toro actually takes into account the implications of such a statement.
 * Western Animaiton//Coraline (book and film). The Other Mother is, in fact and the Other Father is . In the end Coraline is very happy to have her own parents back.
 * Labyrinth: "I wish the goblin king would come and take my little brother away, right now."

Literature

 * The Faerie Queene contains stories of humans (like the Red Cross Knight) who have grown up in Faerie Land because of this trope, aware of their race but not their true identity.
 * Roger Zelazny's 1980 novel Changeling has its plot built on this trope, and its sequel, Madwand. It's a subversion of the typical "Changeling Fantasy" because Pol (né Daniel) acknowledges that the family that raised him was nothing but supportive, and openly admits that his real father was a terrible man when he went off the deep end.
 * In Eloise McGraw 's The Moorchild, the eponymous heroine is actually the changeling. Later on, she restores her foster parents' daughter to them.
 * In the SERRAted Edge 'verse, the fey specifically only do when the children have Abusive Parents. The reason given is that as nigh-immortals, Elves have a very low birth rate and thus value children very highly.
 * Hamilton being a stickler for mythological accuracy, this is mentioned in passing in the Merry Gentry series, but is not practiced by any of the Fey living in the United States, since it might interfere with the driving plot.
 * Variants appear frequently in Jonathan Strange and Mr. Norrell where fairies seem pretty fond of kidnaping in general, but usually don't bother with replacements or stick to children. It comes closest to being played straight with the Raven King who learns magic after being taken as a child, and  who gets an actual replacement.
 * In the YA fantasy Poison, the heroine's baby sister is kidnapped and replaced by a changeling, kicking off her quest.
 * One in John Crowley's Little, Big. After a while, it starts to disintegrate.
 * from Holly Black's Modern Faerie Tales is a changeling, swapped as an infant for a human baby. She later meets the child she was switched with, who has aged only a few years in the Seelie Court.
 * In Tad Williams' novel The War of the Flowers, it is revealed that.
 * Lords and Ladies, being based on The Fair Folk legends, references this -- elves are known to have a habit of stealing children, and while they aren't seen to do it in the book itself, the mere possibility is so infuriating to the usually laid-back Nanny Ogg that she actually (if half-jokingly) suggests Cold-Blooded Torture. Later, in The Wee Free Men, their child-stealing ways get actual page time.
 * The title character of Zilpha Keatley Snyder's book The Changeling spends almost the entire book trying to convince herself and a friend that she is just that.
 * Several of Caitlin R. Kiernan's novels feature "the Changelings": human children who have been abducted from their birth families and inducted into a cabal of subterranean monsters as servants and soldiers. A few of the so-called "Children of the Cuckoo" express longing for normal, human lives.
 * In Good Omens, the infant Antichrist is swapped for a normal human baby this way, with demons instead of fairies. Thanks to the incompetence of an order of Satanic nuns, though, he winds up in the wrong normal human family.
 * In Raymond E. Feist's Faerie Tale, the boy Patrick is taken away by "the shining man" and replaced by a changeling. The family takes the false child to the hospital, and there is a chilling description of the changeling's behavior, and how modern medicine attempts to explain it (that his brain was damaged by fever, that they don't understand how his brain could look like it does under an MRI)
 * In Brenna Yovanoff's debut The Replacement, the main character Mackie is a changeling (or a castoff, or a child left in someone else's bed...the Morrigan gives a lot of names). There is a rather sinister purpose to the child-switching here. The faeries (although they're never named as such) don't want a pet or anything nice like that. No, what they want is a child for the Lady to sacrifice. What's more, the fae kids who get switched into the human world usually don't survive, due to their weaksauce weaknesses of being allergic to iron and blood. Mackie only survived to high school because his older sister loved him so much. The kid who was switched with his girlfriend's little sister? Not so lucky. She does show up in the book, but
 * Poul Anderson's fantasy novel The Broken Sword prominently features a changeling.
 * In the Paranormalcy series, Evie and Jack are these. Jack was stolen by the faeries at a young age, and  Both of their stories bring some of the traditional mythos into it, with them both having Hair of Gold.
 * In The Twelfth Enchantment Lucy's niece is replaced by a strange demonic creature by one of the fairys of the book.
 * In Jack Vance's Lyonesse, Princess Madouc of Lyonesse is a changeling left by the fairies, although a relatively benign sort.

Live Action TV

 * An episode of Law and Order SVU did a piece on a woman with Capgras syndrome (see below). The suspect, a video game addict with a Bastard Boyfriend, kept her daughter under the stairwell and refused to believe she was real, but had been replaced with another -- unless she only heard her daughter's voice. But the minute she saw her daughter, the delusion would set in again.
 * The Torchwood episode "Small Worlds" involved a girl who was a changeling (unbeknownst to her or her family), and the fairies came to get her back.
 * An episode of The BBC's Merlin has a variation on this one, in which a princess is not replaced, but is possessed by a Sidhe in infancy, as part of a plot to put a Sidhe on the throne of Camelot. The princess doesn't know the Sidhe is inside her, although its presence makes her very clumsy and uncoordinated. The plot is that once she's married Prince Arthur the Sidhe will take her over completely.

Mythology and Folklore

 * Older Than Print: The idea of fairies replacing healthy babies with (often sickly) "changelings" (either their own offspring or an enchanted piece of wood made to look like a baby) comes from traditional middle ages European folklore. Some historians believe that the myth appeared as an explanation for what would now be attributed to physical deformities (cleft palettes, birthmarks, six fingers, blindness, etc.), mental retardation (Down syndrome, Williams-Beuren syndrome), or behavioural disorders (ADHD, ADD, Kanner-syndrome, autism, etc.).
 * Folklore also lists ways to identify and "get rid" of a changeling: one of them involves taking the child and throwing it into a hearth fire or onto a hot oven... if it is indeed a changeling, the fairy will change into its true form and flee the house, never to be seen again. (Basically a socially acceptable excuse for poor mothers of disabled children to commit infanticide in medieval times.)
 * Trolls in Scandinavia were also fond of switching their own children for human babies. The way to get rid of the changeling, however, was to treat it horribly and beat it frequently. The changeling's true mother would see the way its child was being treated and rush to undo the swap.
 * In Iceland the Hidden People would steal infants and leave their elderly in stead of the child as a changeling. Much more sensible than leaving your own child, just get rid of senile old pops and get a pretty little young thing instead.
 * In German fairy-tales there are generally two possiblities to get rid of them: 1) treat them horribly (as described above), or 2) doing something really stupid (e.g. cooking water in egg shells), the changeling then would laugh at you (sometimes even taunt you with a rhyme), which broke the spell and forced the fairy to take the changeling back and return the real child.

Music

 * Folk musician Alexander James Adams was once known as Heather Alexander. His stage reason for this is that Heather was the changeling left in his place, of late returned to Faerieland. This is pretty much in keeping with the themes of most of his songs.

Tabletop RPG

 * Changeling: The Lost is all about this. Of course, the faeries in this case don't stop at kids, and the "changelings" of the title are actually the humans they've taken. The Gentry usually just leave something made of detritus and a fragment of their captive's soul in their place. Tragically, such "fetches" not only look human, but often think they're human and have no idea of the truth.
 * Ars Magica. Faeries do the standard "kidnap children and replace them with changelings" routine.

Web Comics

 * In Rêveillerie/Whither, Emelind is a literal changeling, but she considers the universe where she was raised to be her true home.

Web Original

 * Both tropes are explored and played tragically straight in the short story "Changelings and Fairfolk" on Strange Stories About Sad people. http://strangestoriesaboutsadpeople.blogspot.com/2009/10/changelings-and-fair-folk.html

Western Animation

 * Happens to Bloom, the protagonist of Winx Club: First she learns that she's a fairy, and then is revealed that her parents aren't her real parents, and that she's a princess of another world.

Real Life

 * Children with the hereditary genetic Williams-Beuren syndrome are sometimes called "fairy children". They are often smaller than average and show typical facial features: upturned snub nose, full lips, wide mouth, small chin, large eyes set wide apart. Children with blue or green eyes may show a starburst pattern in their iris. They are often mentally retarded but empathic, commonly have strong social skills and great verbal and musical talent.
 * They look like dolls, basically.
 * There is another medical phenomenon that fuels this, known as the Capgras Delusion. Basically, a person with a specific brain injury thinks that their child (or another relative) is not theirs, has been replaced by a Doppelganger who looks alike, and cannot be convinced otherwise (in the age of mythology, elves would be a convenient explanation). It was referenced in The Man Who Mistook His Wife For A Hat.