History Main / MergingMistake

*** In the NonSerialMovie ''Anime/DragonBallZFusionReborn'', 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 TimeLimit ran out.

** Downplayed when [[spoiler: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.

[[folder:Anime and Manga]]

** {{Fusion Dance}}s 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 their the fusion's time limit. In a {{Shonen}} 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 FusionDance - 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 FusionDance down to a tee, and thus haven't failed a single time since.

** 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 FusionDance. But despite their foolproof nature, there exists two cases so far of Fusion going awry.

* In the Creator/RocketJump video ''[[https://www.youtube.com/watch?v=W7Hoz2ZHYZM Every 90's Commercial Ever]]'', being horrifically melted together is a potential side effect of using [[StylisticSuck outdated CGI]] and questionable juice drinks to fast-travel.

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-->--'''South Kai''', ''Anime/DragonBallZFusionReborn''

** This also goes to an extreme with Kevin 11. After absorbing energy from the Omnitrix, he only gets one episode to impersonate Ben's forms, before being unwillingly turned into a [[BodyHorror disturbing permanent mishmash of almost every one of them]] at once.

* In ''VideoGame/KingdomHearts2'', 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).

** {{Fusion Dance}}s must be performed with incredible accuracy, and even as little as an unextended index finger ''will'' cause the FusionDance 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 their the fusion's time limit. In a {{Shonen}} 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.

*** In the non-canon movie ''Anime/DragonBallZFusionReborn'', 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 TimeLimit ran out.
** 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 McGuffin. If neither fusee is a Kai, the fusion instead lasts twice as long under regular circumstances as the FusionDance. But despite their foolproof nature, there exists two cases so far of Fusion going awry.

*** The second happened in ''Anime/DragonballSuper'', between the immortal Kai Zamasu and his non-immortal AlternateTimeline self having GrandTheftMe'd the hero of the series. 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 LogicBomb and begins to degrade with every injury sustained.

* ''Toys/{{BIONICLE}}'': Inverted; Hakann uses the Spear of Fusion in reverse by accident, hitting Vezok and splitting him into Vezok and Vezon.

* In ''VideoGame/KingdomHearts2'', 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, where he is mostly helpless and needs to survive until the mode runs out. On the other hand, there's also a chance the fusion will unlock the even more powerful Final Form (which becomes freely accessible afterwards).

* ''Manga/MaouJouDeOyasumi'': One of the Princess' resurrections sees her accidentally get merged with a demon cat, coming back in its body. The Demon Monk 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.

Note that just because the fusion isn't good, that doesn't mean it is so by a mistake. The fusion can be inheritably bad due of who is being fused with who.

*** 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 FusionDance - the first result was a malnourished, wheezy asthmatic, whilist the second attempt produced a bloated, out-of-shape fattie. Since then, they've got the FusionDance down to a tee, and thus haven't failed a single time since.
*** In the Non-canon movie ''Anime/DragonBallZFusionReborn'', 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 untill his TimeLimit ran out.
** 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 seperate from each other to the series titular McGuffin. If neither fusee is a Kai, the fusion instead lasts twice as long under regular circumstances as the FusionDance. But despite their foolproof nature, there exists 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 occured, and since one of them was a Kai, their fusion was permanent.

* 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 [[https://www.spacetelescope.org/images/potw1537a/ NGC 3921]], [[https://en.wikipedia.org/wiki/NGC_7252 NGC 7252]], or [[https://en.wikipedia.org/wiki/NGC_7727 NGC 7727]]) before finally settling as a noral galaxy.

* In ''VideoGame/KingdomHearts2'', 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,where he is mostly helpless and needs to survive until the mode runs out. On the other hand, there's also a chance the fusion will unlock the even more powerful Final Form (which becomes freely accessible afterwards).

* Fusions in ''Franchise/DragonBall'' come in two varieties; FusionDance, and by way of the divine Potara earrings

** Some Fusions between Gems ([[BizarreAlienBiology 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).

* In ''Franchise/ShinMegamiTensei'' 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 ''VideoGame/{{Persona 1}}''.

* In ''WesternAnimation/SpongeBobSquarePants'' 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.

* In ''Webcomic/{{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 where too incompatible to exist, or committed suicide, though some of them worked out for at least some time.

* ''Anime/YuGiOh'': One episode has Yugi win a card game by fusing his monster with the enemy's different-type monster. As this isn't supposed to happen, the monster becomes weaker every turn.

* The two times [[spoiler:Jasper]] tried fusing, it ended badly for her. The first time [[spoiler: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 [[spoiler:she fused with a corrupted Gem Monster, and ended up contracting its corruption]].

* ''Toys/{{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.

* • The green wizard Carolinus from ''WesternAnimation/TheFlightOfDragons'' sees TheHero 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 TheChosenOne being merged with Gorbash, becoming a modern-day man in the body of a fantasy realm dragon.