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Merging Mistake

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"I know you decided on Gogeta, but in this particular form I think he looks more like Veku."

Fusions are cool. They allow two beings to merge together to create a stronger being. However, fusions are in practice incredibly dangerous. Whether it was done with science, biologically or through magic, even the slightest mistake can make the results less than ideal if you're lucky.

How the fusion can result in a failure varies. Sometimes the result is a mesh of body parts or full of deformities. Sometimes the fusion at first looks fine but is actually incredibly unstable, and will fall apart at some point. Sometimes the fusion wasn't intended to happen in the first place, which just increases the chance of it being really wrong. The only real requirement is that the fusion needs to be physical in nature.

Note that just because the fusion isn't good, that doesn't mean it's necessarily by mistake. The fusion can be inherently bad due to who is being fused with who.

One of the possible results in a Teleporter Accident or in a case of a Tele-Frag, or a case of a faulty Merging Machine. Might result in a Clipped-Wing Angel situation. Shapeshifter Mashup may be the result of this, but just as often it's an intentional result. Compare Assimilation Backfire.


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    Anime & Manga 
  • Fusions in Dragon Ball come in two varieties; Fusion Dance, and by way of the divine Potara earrings.
    • Fusion Dances must be performed with incredible accuracy, and even as little as an unextended index finger will cause the Fusion Dance to go awry, leaving the two fusees in a body that is always comically weak compared to their intended result and have to wait out the fusion's time limit. In a Shōnen series like Dragon Ball, fusions are often done in the midst of battle, leaving the malformed fusion to fight a foe it really cannot handle — as malformed fusions tend to be weaker than their individual parts.
      • Goten and Trunks intended to fuse to be able to fight the arc villain, and actually had the luxury of being in a safe position to practice their Fusion Dance — the first result was a malnourished, wheezy asthmatic, while the second attempt produced a bloated, out-of-shape fattie. Since then, they've got the Fusion Dance down to a tee, and thus haven't failed a single time since.
      • In the Non-Serial Movie Dragon Ball Z: Fusion Reborn, Goku and Vegeta intend to fuse to fight the villain of the movie. However, as Vegeta hasn't fused before then, he forgot to extend his index finger and the resultant fusion could only engage in a game of cat-and-mouse until his Timed Power-Up ran out. This happened again in Dragon Ball Super: Broly where they fail the Fusion twice, forcing to wait half an hour each every time they fail while Frieza gets repeatedly beaten up by Broly for an hour, completely unable to fight back.
      • In Dragon Ball Super: Super Hero, Goten and Trunks decide to fuse to fight Cell Max, since they need all the help they can get. However, since they hadn't done the fusion in so long, Goten and Trunks touch their index fingers in the wrong position, causing Fat Gotenks to appear. On the plus side, it was useful to reveal Cell Max's weak point.
    • Potara earring fusions are foolproof, and to fuse you need only have the two fusees wear one matching earring on opposite ears. If within range, they will fuse perfectly into a much more powerful fusion — and if at least one of the fusees is a Kai, the new fusion is permanent barring a wish to separate from each other to the series' titular MacGuffin. If neither fusee is a Kai, the fusion instead lasts twice as long under regular circumstances as the Fusion Dance. But despite their foolproof nature, there exist two cases so far of Fusion going awry.
      • The first was mainly because it was never meant to happen in the first place: the elder Kai fused with an old witch who thought his earrings looked fancy, reached out, took one from him, and put it on her corresponding ear. By the time she reached for the second the fusion occurred, and since one of them was a Kai, their fusion was permanent.
      • The second happened in Dragon Ball Super, between the immortal Kai Zamasu and Goku Black, his non-immortal Alternate Timeline self having Grand Theft Me'd Goku. While their initial fusion definitely thrashed anyone who stood against it, it highlighted a flaw with the Potara earrings: if one of the fusees is immortal, and the other is not, the fusion suffers the biological equivalent of a Logic Bomb and begins to degrade with every injury sustained.
  • In the Lyrical Nanoha series, Fusion Dance occurs mainly with "Unison Devices": magical Robot Girls who are able to physically merge with the bodies of their Lords in order to dramatically boost their combat capabilities. However, if the Lord is incapable of handling the power of the Unison Device, the Device instead takes over their body completely and can use it as she sees fit. This is what happens in Magical Girl Lyrical Nanoha A's during the first Unison between Hayate and Book of Darkness/Reinforce: Hayate, still being a muggle at that point, has no way of controlling the Book through regular means, and is taken over by it.
  • Sleepy Princess in the Demon Castle: One of the Princess' resurrections sees her accidentally get merged with a demon cat, coming back in its body. The Demon Cleric manages to undo it, but not until after the cat-Princess wrangles him into smuggling her back to her cell to spend several hours sleeping under the kotatsu.
  • Yu-Gi-Oh!: One Duel against Kaiba during the show's first season has Yugi fusing his undead monster with his opponent's living monster. The monsters can't properly combine, so Kaiba's monster becomes weaker every turn.

    Comic Books 
  • Spider-Man: One of Spider-Man's most iconic foes, Doctor Octopus, came to be when scientist Otto Octavius was struck by radiation while wearing an advanced mechanical arms harness, causing them to fuse to his body and be controllable by his mind.
  • In the Teenage Mutant Ninja Turtles (Mirage) miniseries Bebop and Rocksteady Destroy Everything a time travel mishap leads to temporal duplicates of the eponymous villain duo getting a second dousing of mutagen while in contact with each other. The result is a hideous amalgamation of their bodies supplementary material calls Bopsteady.

    Fan Works 

  • The Fly is a classic in terms of Teleporter Accident fusions, with Andre ending up having his hand and head switched up with that of a fly.
  • Captain Underpants: In The Big Bad Battle of the Bionic Booger Boy, Kid inventor Melvin attempts to fuse himself with an advanced robot of his own making, intending to turn himself into a bionic super-boy. But just as the fusion process is commencing, Melvin's cat allergies are triggered and he sneezes boogers out his nose, causing them to be fused as well and turning him into the Bionic Booger Boy.
  • Robert Sheckley has a short story (later expanded into a novel called Alchemical Marriage of Alistair Crompton) where a person who was split into several personalities with artificial bodies as a treatment for schizophrenia seeks them in order to reintegrate. At the end, he finds them all and reintegrates... except they don't integrate into his personality but create a completely new one.

    Tabletop Games 
  • Warhammer: Vilitch was the downtrodden younger brother of Thomin, apprenticed to the tribe's shaman while Thomin received the best warrior training in preparation for his becoming the tribe's chieftain. Vilitch prayed to Tzeentch that their fates might be switched. Instead, Tzeentch melded their bodies together, Vilitch casting spells and Thomin's body removing nearby threats. Vilitch saw no problem with this, using his newfound strength to enact a Roaring Rampage of Revenge against All of the Other Reindeer.
  • The Merger Inheritance from Beast: The Primordial. A Merger occurs when a Beast collapses his own Lair, pulling his Horror into the real world and merging it with his body. While the Merged Beast does have increased power, the transformation destroys the Beast's human mind and body, leaving an inhuman monster with at best a few instincts and memories inherited from its human life.
  • The Ritual of Union in Unknown Armies. The intent of the ritual is to fuse two people to create one person with the memories and abilities of both; if it fails badly enough, the result is a shapeless, insane mass of flesh instead. Even when it works the resulting being tends to be mentally unstable due to having to deal with two conflicting sets of memories.

  • Mixels has one fusion option known as "Murps", where the result ends up a misshapen creature that still has the abilities of the original tribe members, but is unable to properly utilize them, often causing destruction to either themselves or to their environment.
  • BIONICLE: Inverted; Hakann uses the Spear of Fusion in reverse by accident, hitting Vezok and splitting him into Vezok and Vezon. This results in Vezok losing much of the intelligence that made him a Genius Bruiser, while Vezon becomes an incredibly intelligent being, but lacking in his original self's powers, most of his physical strength, and what sanity there was.

    Video Games 
  • Day of the Tentacle: The finale of the game involves Bernard, Laverne and Hoagie climbing into one timemachine to chase down Purple Tentacle in the past. Dr. Fred tries to object, citing The Fly as a reason as why they should not go into the time machine. The end result involves the trio becoming a three-headed fusion of themselves with Hoagie's fat upper body and Laverne's gangly lower half. The epilogue reveals that they didn't actually fuse together, but they're all tangled together and most of their body parts are stuck in Hoagie's shirt.
  • Chaosmon from Digimon is a result of an incomplete DNA Digivolution between BanchoLeomon and Darkdramon/Valdurmon, leaving it with two Digicores instead of a combined one, and is considered a Game-Breaking Bug in-universe. UltimateKhaosmon is another example, this time being a fusion of BanchoLeomon, Darkdramon, Valdurmon and Kentaurosmon, whose powers are too much to contain in one body, leaving it being a withered out creature with four massive arms and two giant eyes which are actually two Digicores that it can't contain in its body.
  • In Disgaea 4: A Promise Unforgotten, Mao's Evil Transformation skill has him trapping his targets into a Merging Machine with a Slime, with the end result being a humanoid being wearing the Slime's skull which speaks gibberish. Which then explodes.
  • In Conway's Game of Life, there are several ways in which a "glider synthesis" (colliding gliders together to produce new objects) can go wrong. To be valid, a synthesis must be able to be rewound indefinitely while still eventually leading to the same result. If not checked for, an attempt to rewind the synthesis will cause gliders traveling in different directions to collide prematurely. Even if the synthesis is valid, a single glider being out of place by even one cell or one generation can ruin the synthesis and produce a completely different object.
  • Fear & Hunger:
    • A group of guards attempted to form a Marriage to empower themselves, but instead merged into a massive, deformed pile of body parts called the Human Hydra. The player can feed a few party members to them, with no benefit.
    • Buckman and Ser Seymour will attempt to form a Marriage if the player talks to them when they regroup in the basement. The Marriage doesn't go well, and the two mutate into a hideous, non-functioning being.
  • In Kingdom Hearts II, Sora can combine with either Donald or Goofy (or both) to get a power boost in combat. Sometimes, however, the fusion fails and Sora goes into Anti-Form instead. Anti-Form has some advantages over normal Sora and the other Drive Forms (extremely fast movement and attacks) but also a lot of disadvantages (hard to control, takes increased damage, can't regain health, can't manually end the transformation unless out of combat or the Drive Gauge runs out, it consumes the entire Drive Gauge). On the other hand, there's also a chance the fusion will unlock the even more powerful Final Form (which becomes freely accessible afterwards).
  • One of the biggest threats in Martian Reunification Gothic is a virus the three protagonists are infected with at the beginning that forcibly merges other people with the virus together into hideous monsters, forcing them to stay in different rooms than each other. Fused monsters born out of scientists are also recurring enemies.
  • In the Shin Megami Tensei series, there is usually a chance that fusing demons ends up in a fusion accident. While the specific results vary, it usually results in you getting a completely different demon than what it really should have been. In some cases, you can only get access to certain demons through a fusion accident like Zealot demons or Fool Personas in Persona.
  • At the climax of TRON 2.0, the three F-con executives try to enter the cyberspace world in a last-ditch effort to stop the Player Character from thwarting their plans. However, because the correction algorhythms of the digitizing laser have been removed at this point, they end up merging into a three-headed monstrosity that is defeated by the Player Character and is trapped on a storage medium afterwards.

    Web Animation 
  • In the second half of the sixth episode of Confinement Connor and several other people escape from the infinite IKEA using a staple gun with the ability to teleport what it shoots. It also turns out that if it is used to teleport multiple people in a short time it has the side effect of causing them to fuse together into a mass of Body Horror. Connor is able to escape from the fusion thanks to his regeneration ability while everyone else isn't so lucky.

  • In Homestuck, Gamzee throws the dead bodies of his friends, along with some other dead characters in the alpha kids' kernelsprites, which fuses two of them together as ghostly spirits. Most of them were too incompatible to exist, or committed suicide, though some of them worked out for at least some time.

    Web Original 
  • Whateley Universe: The Fury Twins, who merge into one being, but one time, they got stuck part-way defusing, and needed Mad Scientist help to get unstuck.

    Web Videos 

    Western Animation 
  • In the Ben 10 episode "Dr. Animo and the Mutant Ray", this happens when Ben accidentally breaks part of the Omnitrix, resulting in fusions of his alien forms that cause more harm than good - Four Arms gets merged with Stinkfly, resulting in a hunk of muscle that can't fly very well; and Ripjaws ends up fused with Heatblast, which goes about as well as you'd expect.
  • DuckTales (2017): The Stone of What Was has the power to fuse two creatures that touch it at the same time into one being. While many of its creations are mere Mix-and-Match Critters, some of Don Karnage's pirates fuse with animals (an ant, a snail and a parrot) and each other into horrifying freaks.
  • The green wizard Carolinus from The Flight of Dragons sees The Hero plummeting to certain doom, and docile dragon Gorbash unable to descend fast enough to catch him. Carolinus tries to invoke a magic spell to speed up Gorbash, but being pressed for time, Carolinus can't assemble the Latin phraseology completely, and concludes with a general-purpose "Kala!" The result is The Chosen One being merged with Gorbash, becoming a modern-day man in the body of a fantasy realm dragon.
  • The Grim Adventures Of KND: After Billy confuses the Delightfulization chamber with a portable bath he and The Delightful Children from Down the Lane get fused into a Grim Reaper that assimilate almost every kid on Cartoon Network.
  • In the episode "Canderemy" from Phineas and Ferb, Candace and her crush Jeremy are fused together at the waist by one of her brothers' inventions. Eventually, the boys zap them together to form one bizarre fusion with two hair colors and four eyes.
  • In the last season of the original Reboot series, Bob merges with his broken Keytool Glitch because that's the only way to make use of Glitch's Keytool abilities which are needed to escape the Web. In the revival season that takes place after the original series it's revealed that the merging was unstable precisely because Glitch was damaged. Glitch-Bob was unstable as a result and risked total fragmentation if he kept using his powers.
  • In SpongeBob SquarePants episode "SquidBob TentaclePants", SpongeBob and Squidward get accidentally fused together in Sandy's teleportation device. In the end of the episode, everyone got fused together when Squidward tries to mess with an unfusion device.
  • Steven Universe:
    • Some Fusions between Gems (which have their own personalities, while also being an amalgam of their component Gems) are very strong willed, and can overwhelm their components and refuse to defuse (Sugilite being an example early in the series, as she refused to separate back into Garnet and Amethyst and attacked Pearl in her first appearance).
    • The abominations that are the cluster experiments, which turned out to be horrifying amalgamates of shattered gem shards in a state of artificial forced fusion. The full-sized cluster that was buried in the Earth, which is comprised of millions of gem shards, would have formed big enough to destroy the Earth from the inside. Good thing it didn't.
    • The two times Jasper tried fusing, it ended badly for her. The first time she forcibly fused with Lapis Lazuli to form Malachite, but didn't count on Lapis taking over and chaining themselves to the bottom of the ocean. The second time she fused with a corrupted Gem Monster, and ended up contracting its corruption.
    • Downplayed when Garnet is first formed. She's not malicious or monstrous, but her hair and clothes are a messy combination of her components, contrast with the more orderly look she has at every other time period.
  • In Teenage Mutant Ninja Turtles (1987), this is how Baxter Stockman underwent his infamous fly transformation. When Baxter was sent to Dimension X, Krang didn't see any use for him, and so threw him into the Technodrome's Disintegrator Unit. However, a fly that ended up coming to Dimension X with him ended up in the unit as well, causing a malfunction in which Baxter was cross-mutated with the insect, leaving him in the form he would remain for the remainder of his appearances.

    Real Life 
  • The product of an interaction, or especially a merger, between two galaxies (and the closer they're in mass, the larger the mess is) is a very distorted system with tidal tails of stars and other features (see for example NGC 3921, NGC 7252, or NGC 7727) before finally settling as a normal galaxy.