Organ donation is a noble thing. Lots of us have little cards that tell the doctors that if we have life rudely yoinked out from under our feet, they can take what's left of us to make sure that the same tragedy [[BillyNeedsAnOrgan doesn't befall someone else]]. Some forms of donation - like donating a kidney - can actually be done while still alive, which is just as brave, especially since you'll be pottering around the planet for years to come and are still willing to hand over an internal organ so that someone else can live.

Most of us agree though, that it is not something we would want to have forced on us while our hearts are still beating, thank you very much. At that point, the kind act of donation becomes little more than mutilation. Cue fiction.

This character exists for one reason - as "spare parts" for another character. It usually turns up in sci-fi/horror settings, but occasionally makes a guest appearance in emotional drama. They can be raised to cherish their purpose and perfectly content with their (usually fairly short) existence, or they can [[ScrewDestiny rage and fight against it]]. The qualifier is, the only reason they were born is because someone else might need their various body parts at some point. Rather depressing.

This is a pretty legitimate source of angst for the character who's treated like a spare tyre (and usually with about as much consideration for their feelings). This is ''their'' body - the one they were born with, with all their own genetics and personality traits - but as far as the people around them are concerned, the Walking Transplant's very flesh and blood are the exclusive property of whoever they were created to be the donor for.

FridgeLogic begins to creep in once you remember the time and resources necessary to raise a human to adulthood, the incalculable variables that could render their organs unusable, and the difficulty of ensuring that said clone remains in the dark on the until the original ''needs'' a new part is the equivalent of building a brand new car solely for it to be cannibalized for spare parts. That's all bad for drama, though, so it's usually ignored.

Related to, but not to be confused with, OrganTheft. In reality, the idea of a child being a "walking transplant" is often used to argue against the possibility of "DesignerBabies" - although there have already been babies screened and selected before birth ''specifically'' to donate to an older sibling (usually in the form of some "replaceable" material, like bone marrow and blood). Sometimes combined with TrulySingleParent. CloningBodyParts is an attempt to make compatible transplants without the ethical issues involved here.
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!!Examples:

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[[folder:Anime and Manga]]
* ''Manga/PetShopOfHorrors'': A rather dark story (even for this series...) reveals that Count D's father engineered a "sister" for D [[spoiler:(she's actually an orangutan)]] to provide him with "spare parts," since D apparently suffers from some kind of SoapOperaDisease that is introduced and [[WhatHappenedToTheMouse then forgotten about]]. She is eerily proud of her purpose.
** [[spoiler:D's disease seems to relate to a later-implied need to drink blood. At the end of the story, he's shown drinking a glass of what Chris assumes to be "cranberry juice", in his "sister's" name.]]
* Adorea of ''Manga/FrankenFran''. Under all those bandages is a body covered in zippers for easy access to any emergency spare body parts that Fran might need. Fran replenishes her supply by [[spoiler:letting Adorea swallow people who are nearly dead]].
* Somewhat TearJerker example: in ''Anime/NeonGenesisEvangelion'', Rei invokes this trope on '''herself''' [[spoiler:for [[CloningBlues obvious]] [[BackFromTheDead reasons]]. Ritsuko even refers to [[EmptyShell Rei's clones]] as spare parts. The unsettling part? [[EmotionlessGirl Rei-03]] remembers the deaths of [[CreepyChild her]] [[{{Kuudere}} predecessors]] and wants to [[GetItOverWith die herself]], [[KilledOffForReal permanently]]. By finale, it seems she finally got her wish.]]
* A major plot element in ''Anime/{{Vandread}}'': [[spoiler:Entire worlds were set up for their peoples to unknowingly provide specific replacement organs for the humans of future-Earth - the homeworlds of the ''Vandread's'' crew, for example, were male-only and female-only and provided their respective reproductive organs.]]
* One episode of ''Anime/GhostInTheShellStandAloneComplex'' includes a ranch full of genetically modified pigs with organs tailored for human transplant. Each one is designed for a specific customer, but if the customer doesn't need anything within the pig's lifetime, the organs can still be distributed to compatible recipients.
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[[folder:Comic Books]]
* In the very good but largely forgotten Creator/DCComics early 1990s version of ''ComicStrip/FlashGordon'', the Yellow race of Mongo were acculturated to view their fate as organ replacements for the ruling Grays as the equivalent of going to Heaven.
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[[folder:Film]]
* The whole premise of ''TheIsland'' and ''Parts: The Film/{{Clonus}} Horror'' (the similarity between the two sparking a lawsuit). Just to ram home how inhumane the treatment of the clones is, in ''TheIsland'' we see a baby being removed from its clone mother to be given to the "original" (who couldn't conceive) - after which the clone is "[[DeadlyEuphemism disposed of]]". For further effect, a clone who wakes up on the operating tables as his organs are removed is harpooned and dragged back so they can finish the job. The "sponsor" (original version) of the main character refers to his clone as "his insurance policy," underlining the fact that the clones are seen as sub-human, and the property of whoever pays for them.
** However, the "sponsors" don't know what the cloning process is like; the guy in charge (and main baddie) has told everyone that the clones have no mental processes to speak of, and essentially only exist as bags of organs. And he'd much rather the real story never came out...
** In ''Clonus'', the originals know ''damn well'' what the process is like - it's implied they're TheIlluminati if you pay attention - and they just don't care. The clones are treated somewhat nicer than in ''The Island'', though, up until they're stripped for parts.
* ''Film/NeverLetMeGo'' follows the same basic principles, but differs from other movies in that the clones are told about their intended purpose. Not that they're any happier about it, but as the film is quite bleak, they usually eventually resign to their intended purpose and end up dying.
* Used for BlackComedy in one scene of ''Film/MontyPythonsTheMeaningOfLife''. A pair of guys go to an organ donor's door and cut him open to get his liver.
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[[folder:Literature]]
* JodiPicoult examined this in ''Literature/MySistersKeeper''. Anna is a designer baby, genetically engineered to save the life of her older sister, Kate. When Kate's kidneys fail, Anna's parents expect her to hand over one of her kidneys. She sues them in order to gain control of her own body [[spoiler:although it is later revealed that big sister - and the beneficiary of Anna's donations - Kate had much more trouble with this arrangement than Anna did]]. The attitude of her mother, in particular, can be pretty chilling - at the best of times, Sara is hugely insensitive and [[ParentalFavoritism so obsessed with Kate]] that she fails to see the dire straits Anna and [[TheUnfavourite older brother Jesse]] are in...but at worst, there is something downright creepy in her tendency to break Anna down into her component physical parts. Two examples stand out: Even at Anna's birth, Sara totally fails to mention her newborn as she rushes off to oversee Kate's treatment thanks to Anna's umbilical cord. Still creepier is when she denies Anna a chance to go to hockey camp in case something happens to Kate - since when the next crisis strikes "we will need Anna - her blood, her stem cells, her tissue - right here."
** The film and book end differently. The film [[spoiler:ends with Kate, sick of the constant surgeries and tired of watching Anna being tortured in order to keep her alive, arranging to die, thus freeing Anna.]] The book [[spoiler:ends with Anna winning her case, only [[DiabolusExMachina to be rendered brain-dead when a car hits her, at which point Sara has both her kidneys put into Kate]].]]
* In the novel and 2010 movie ''Literature/NeverLetMeGo'' by Kazuo Ishiguro, the students of Hailsham are all [[spoiler:clones designed to be this, and when they graduate from school they are expected to become donors until they die, a fate which they passively accept as what they are supposed to do]]. They develop their own GallowsHumor to deal with the horror of their situation, but overall it's a more melancholic/tragic, rather than horrific, take on the subject.
* In the ''Literature/VorkosiganSaga'', on [[WretchedHive Jackson's Whole]], there's a trade in creating beautiful, aged-up clones of the powerful and rich and then scooping out and replacing their brains with those of their progenitors. [[spoiler:The main character's brother,]] Mark, who is a clone for other purposes, was raised amongst these clones and has set out to destroy the industry. At first he tries to do so physically, but when that doesn't work set about to do it economically, by obsoleting the procedure or otherwise making it unfeasible.
** Let's stress this point. Old, rich degenerates have clones made of themselves and make the clones undergo different body-morphing procedures until the time comes when their brains are scrapped and the old geezer's brain is transplanted in. All the while, the kids think they are in an exclusive boarding school and all of them are told that they are heirs of [=VIPs=]. Then, when they reach physical maturity at the age of 10, they are called to "meet their parents", and they are never seen again...
* The "Unwinds" in Neal Shusterman's ''Literature/{{Unwind}}''. There was a war between the pro-choice and pro-life people in America. A compromise was reached when the government decided that anybody from birth to 13 could not be killed, but from 13 to 18, they could be retroactively aborted, or "unwound". All their body parts (not just organs) were taken away from them and given to other people. The main characters of the book are volunteered for this process for different reasons. Connor is a troublemaker. Risa, who is a ward of the state, has reached the peak of her musical ability so she is going to be unwound to save costs. Lev is volunteered because his parents are strict Christians who give 10% of everything to God, including children, and Lev is the tenth child.
* The kids' book ''Literature/CloneCatcher'', by Alfred Slote, centers around the use of clones for this purpose; the rich have clones created and then raised in secure compounds until their organs are needed.
* ''Literature/HouseOfTheScorpion'' features entire PeopleFarms for this purpose. Those used are all [[CloningBlues clones]], which "aren't human" anyways. And as a rule they're deliberately brain-damaged shortly after birth so as to make sure they don't seem human. The main character is a rare exception, [[spoiler:though still a potential involuntary organ donor, because his "father" is just that sort of guy.]]
* This is the basis of ''Literature/{{Spares}}'' by Creator/MichaelMarshallSmith.
* In ''Literature/{{Patternist}}'' by Octavia E. Butler, the immortal soul eating {{Body Surf}}er Doro attempted to create a new race of human telepaths through a selective breeding program extending from the early ages of human history towards the present so he can have new bodies to possess. He is eventually HoistByHisOwnPetard as one of his group of eponymous network telepaths struggle beyond his control and absorb him instead.
* In TheGodwhale, the protagonist loses his legs and gets frozen until his condition can be fixed. A few centuries later, he is defrosted in order to become a settler on another planet. The new legs are ready... but when the guy learns they are attached to a boy who will have to die for him to get them, he asks to send the boy as the settler, and himself back into the freezer.
* In ''Literature/OryxAndCrake'' pigoons are chimeric pigs engineered to have multiple redundant human-compatible organs for transplants. [[spoiler: In [=MaddAdam=] it turns out that the human brain cells for Alzheimer's patients makes them sapient, and the Crakers and Gardeners make an alliance with them following a few "misunderstandings".]]
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[[folder:Live-Action TV]]
* There is an episode of ''Series/{{CSI}}'' where a girl is found dead in the desert; turns out she was conceived as a bone marrow donor for her older brother. Older brother felt bad about this and so, in a total failure of logic, killed her.
** He was a staunch Catholic and she was so depressed by her life she was considering suicide. His first plan was to make the parents agree to stop using her as his donor and let him die. They went back on their promise when he had kidney failure, stating that they had only agreed to stop treating the original cancer, not the side effects and were going to force her to donate a kidney. He killed her, confessed to a priest, then planned to die from his disease, thus ensuring both went to heaven, instead of her going to hell as a suicide.
* ''Series/StarTrekEnterprise'' cloned Trip so Dr. Phlox could get certain brain parts for replacement. The problem was that the clone retained Trip's memories and didn't want to die...
* ''PrivatePractice'':
** One episode has a mother, six months pregnant with the walking transplant, have her [[LittlestCancerPatient terminally ill son]] need a blood transfusion within the week or the son will die. Their baby girl has not developed enough, so what does the mother do? [[spoiler: She jabs a knitting needle up her birth canal to make her waters break. And then the baby dies.]]
** Another episode featured a couple with a walking transplant baby who was intended to save his twin sisters with leukemia. When he turned out to have only enough cord blood for one sister, the parents were asked to ''choose their favourite'' to treat!
* ''Series/{{Sliders}}'':
** Used in one episode, which has our Quinn mistaken for a clone of the world-of-the-week's Quinn - who needs new eyes after being blinded in an accident. The clones are fully alive and... it basically predicted ''TheIsland,'' including [[spoiler: ending with the practice being exposed and stopped entirely. We end with ''three'' Quinns in one scene for the first time: ours, the real clone, and this world's Quinn, who will remain blind for life but is perfectly okay with it if the alternative is murdering/maiming another human being.]]
** Another episode features a world where all people or a certain age are considered potential organ donors, whether they want to or not. Each receives a non-removable tracking bracelet that activates when a compatible organ is needed. Then a special police unit arrives to take the "donor" into custody. The doctors behind the program are shown to be corrupt, often using the system to get what they want (i.e. if you don't do what I say, I'll activate your bracelet and take your heart or liver).
* ''Franchise/LawAndOrder'':
** Done in the original ''Series/LawAndOrder'' when a doctor is revealed to have been implanting IVF patients with his own sperm, which screws up one couple's plan to save one child by conceiving another. [=McCoy=] briefly considers indicting the doctor for the child's death.
** In ''Series/LawAndOrderCriminalIntent'', there was this one guy who goes around literally giving away pieces of himself since he had given away pretty much everything else. [[spoiler: More specifically he was donating his parts to people he felt would change the world for the better...but only if they did. He killed the VictimOfTheWeek (or rather shot her in a way that would cause brain death so she'd become a viable organ doner) because she gave up on her work to become a housewife.]]
* ''Series/StargateSG1'': One of the reasons the Goa'uld System Lords take their lo'tars (trusted human servants; literally means "you, human") everywhere with them is to have a spare host in case their current one expires for any reason. In this case, the lo'tars are donating their entire bodies. However, most are brainwashed (as in indoctrinated from birth, not mind-controlled via {{Phlebotinum}}) into believing it to be an honor. They are also expected to be knowledgeable about Goa'uld politics in order to avoid any faux pas.
* ''Series/{{Heroes}}'': Mohinder was conceived to be a blood donor for his sister. Although by the time he was born she was too far gone and was always a point of contention between him and his father.
* On ''Series/{{Neighbours}}'' Nicola was conceived for the purpose of saving her sister Miranda's life. This is a major factor in her psychotic break shortly before she left the show.
* The ''Series/{{Firefly}}'' episode "The Message" features a variation in which a character is used to smuggle cloned organs. (They're smuggled because the technology is still experimental and has yet to go through Space FDA approval.) A surgeon scooped out his original wetware and put it on ice, the plan being to put it back at his destination.
* On ''Series/OrphanBlack'', a major plot is whether or not to let Sarah's daughter Kira donate stem cells to Cosima, who is suffering from the mysterious illness that many of the clones have. Kira is the best match, since Sarah and Cosima are clones.
* ''{{Smallville}}'': This is the entire point of the clones of Lex Luthor. They were made so that their body parts and organs could be used to "rebuild" Lex's body after he was severely wounded in an explosion. When Lex "Prime" was killed permanently in season eight, the clones were still used for this, but this time to create a stable clone of Lex that could take his place (and have all of his memories). And if it wasn't all disturbing enough, the project ran out of clones before they could take a heart, because the last clone had already been hidden from Lex's people, so the [[AlternateUniverse Earth-2]] version of Lionel Luthor, looking to get his son back, took this trope even further- by trying to take the heart from [[spoiler: ''[[OffingTheOffspring his own]]'' ''[[TheUnfavorite daughter]]'']].
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[[folder:Video Games]]
* Producing these is revealed to have been the original purpose of the laboratory where ''[[VideoGame/TwelveThirteen 1213]]'' takes place [[spoiler: before the world ended]].
* A major plot point of ''VideoGame/MassEffect3: Citadel''. [[spoiler:During Cerberus' project to revive the dead Shepard in ''VideoGame/MassEffect2'', they cloned him/her in order to have a complete set of replacement organs for Shepard in case something went wrong. The clone was kept sedated, but around the same time the ''Normandy'' SR-2 hit the Collector base the clone was revived by and escaped with a disgruntled Cerberus employee, and is the expansion's ArcVillain.]]
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[[folder:Western Animation]]
* ''WesternAnimation/TheVentureBrothers'': Dr. Venture has this as a partial purpose for his sons. Season 2's premiere [[CloningBlues reveals why this]] [[ItMakesSenseInContext is okay]].
* Played for laughs in ''WesternAnimation/{{Futurama}}''; the Professor keeps Amy around because she is of the same blood type. He views all his employees this way: "Damnit, Hermes, just jump already. Stop hogging that healthy liver!"
* In one episode of ''WesternAnimation/UglyAmericans'' Mark talks about how clones were originally made for this purpose, but now they're used for a variety of other reasons such as [[TwinThreesomeFantasy marital aids]]. At the end of that episode [[spoiler: Mark's evil clone is chopped up for spare parts after he's executed for murder, Grimes gets his eyes and legs to replace the ones the clone destroyed.]]
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[[folder:Real Life]]
* Possibly on its way to aversion in RealLife. With the rapid advancements being made in [[http://en.wikipedia.org/wiki/Tissue_engineering tissue engineering]], ''TheIsland''-style cloning people for parts makes absolutely ''no'' sense. The method of building organs discussed in ''2057'', by using a "cell-jet" printer, is actually being worked on.
* To avoid the immune system attacking the transplanted tissue, some scientist have actually mentioned the posibility of cloning the patients and harvesting the stem cells from the embryos before they get any chance to get angsty and [[TurnedAgainstTheirMasters turn against their creators]].
* Along the same vein, some scientists are also trying to use the stem cells that can be found in an adult's body (like, for example, in the bone marrow, or in certain skin layers) for these purpose, allthough this is slightly harder as those cells are multipotent and can only turn into certain types of other cells. Some scientists are trying to reverse them to their pluripotent state, though.
** The 2012 Nobel prize for Medicine went to a scientist who did reverse adult, multipotent stem cells to pluripotent stem cells that can divide into any cell in the body - but not embryonic tissues, so they can't create a new human being anyway.
* Possible aversion of this trope with experiments with stimulating [[http://cmbi.bjmu.edu.cn/news/0309/154.htm unfertilized egg cells]] to divide and create stem cells. Possibly inspired by teratomas, which arise from germ cells and can contain ''any'' kind of tissue.
* Advances in genetic engineering may eventually make it possible to breed domestic pigs with human-analog histocompatibility traits. Most internal organs are similar in pigs and in humans, so such animals would be ideal four-legged examples of this trope, with few ethical constraints and much faster turnaround-time to grow them to adult size.
** To be clear, there is no record of a successful xenotransplantation. Organs grown in the pigs would need to be nearly identical to the recpients' genes to not be attacked by (and attack) the former, and the pigs' own immune systems would be likely to attack any alien organs growing within them. Once again, growing transplants from scratch may be more plausible.
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