History Main / SpannerInTheWorks

(Note for Americans reading this: "Spanner" is the British English word for what you would call a "wrench", with the added benefit of it being slang for a stupid person. It has nothing to do with a {{Long Runner|s}} in development. The equivalent American phrase specifically involves a ''monkey'' wrench, known in the UK as a gas grip -- "He really threw a monkey wrench into my plans.")

They are the bane of the ClockKing. They are the worst nightmare of {{Manipulative Bastard}}s everywhere. They are the monster in the closet that haunts TheChessmaster every time they close their eyes. Their very presence causes even [[XanatosGambit David Xanatos himself]] to [[OhCrap rethink all of his life choices in the blink of an eye]].

* In ''VisualNovel/ShallWeDateNinjaShadow'', Makoto's route has [[spoiler: his AntiVillain brother Toru]] deploying an EvilPlan where he [[spoiler: frames Makoto for murder to disband the Nagasaki Vigilantes, isolate his younger brother and force him to join his rebel cause.]] It works scaringly well despite Saori's efforts, until... [[spoiler: Ukyo decides to call the Edo Vigilante group and ask them for help. The moment Kinshirou and Wakasa from the Edo group step in is the moment they strt working hard to learn what's going on, leading to them clearing Makoto's name and giving him [[BattleCouple and Saori]] the chance to confront, fight and capture Toru.]]

[[folder:Fan Works]]
* ''Fanfic/AbraxasHrodvitnon'': Godzilla is a secondary character rather than the protagonist of this story, but he's responsible for kicking off the entire plot when he ripped San's head off of Ghidorah during the events of ''Film/GodzillaKingOfTheMonsters2019'', leaving San and the OnlyMostlyDead Vivienne inside his head separated from Ghidorah's malevolent influence before being reborn as the two-headed [[AdaptationalHeroism Monster X]].
* ''Fanfic/AdventuresOfASuperFamily'': Lex Luthor's plan to destroy an upcoming company rival by sabotaging its experimental plane engine during an exhibit gets foiled when an unknown super-hero suddenly shows up and saves the plane.
-->The plan had been so straightforward as to almost be laughable. Sabotage the plane's engine, making it crash, then blaming it on the new navigation system. Sure, any engineer worth his salt would say that a faulty navigation system would not make an engine explode, but with the plane splattered across half of Metropolis and a few hundred people dead in the crash, no one would have listened. The company would have never recovered from this public relations disaster.\\
But the plan had not worked. All because some comic book superheroine had chosen that exact moment to step into the limelight. Was this a joke? Was some cosmic deity playing a prank? The world gains a superhero just in time to sabotage his plans?
* ''Fanfic/AdviceAndTrust'': Shinji and Asuka end up ruining Gendo's plans by [[DefusingTheTykeBomb befriending Rei]], although this happens long before his plans are put into action. And ''everyone'' is completely unaware of the implication of this, meaning that they spend several chapters trying to figure out how to stop him, and he still thinks that he's in control of the situation, despite the fact that he's already lost.
* ''FanFic/AnAlternateKeitaroUrashima'' repeatedly derails his grandmother's attempts to manipulate him simply by letting others know how [[ManipulativeBitch manipulative]] she is. As a result, when she shows up and starts spinning her webs, she winds up proving him right.
** Mokoto also runs afoul of this when she threatens Keitaro one time too many. When she draws her katana, she's unaware that [[spoiler:some police officers are passing behind her and witness it]].
* ''Fanfic/AndTheGiantAwoke'': When Euron and Tywin make their plans for dealing with each other -- raid into the other's lands to force the enemy to retreat and fight in their own terms -- all of them are for nothing when a storm forces both fleets to change course and they meet in the middle of the sea.
* Ranma becomes one for not only Minaka and his Sekirei game in ''[[https://www.fanfiction.net/s/11701126/1/Anything-Goes-Game-Changer Anything Goes Game Changer]]'' but Higa as well, the latter without even being aware of the man's existence. Besides Ranma interfering with unfair battles, mostly preventing Sekirei from being forcibly winged, he and Uzume pose for pictures for Nabiki to raise money (to cover his living expenses). Uzume's cut is enough for her to pay off her Ashikabi's hospital bills, which were being used by Higa to blackmail her.
* ''Fanfic/{{Atonement}}'': The Slaughterhouse Nine might have gotten a new member in Ruin had Mnemosyne not interfered, turned Burnscar against the rest of the Nine, and freed Hunter.
* ''Fanfic/AvatarTheLastAlicorn'': Sweetie's plan to take over Fillydelphia and eliminate all the water and fire benders along with the avatar and the great dragon would've gone perfectly, if it wasn't for AJ learning metal-bending, allowing her to escape, and provide Team Avatar an avenue to escape.
* ''FanFic/TheBridge'' gives a borderline humorous example in an otherwise completely serious situation. [[BigBad Bagan]] has set up an elaborate XanatosGambit that would work out in full to both secure more power for himself as well as kill [[BigGood Harmony]]. A crux of it was keeping a displaced Monster X separated from his comrades and put into the Equestria Girls world, where he'll be weaker in his human form and thus easier to kill by Bagan's agent, Enjin. One bystander messed it up and they weren't another kaiju nor an Equestrian hero intervening in the fight. EG!Photo Finish happened to be at the scene of a battle between X and Enjin at a hospital and took some pictures, thinking it was a movie stunt being filmed. Days later when an ally of X was in the same realm but dozens of miles away, she bumped into Photo, saw the pictures and recognized X in the images; and was able to alert her allies that she'd found him and he was in trouble. Bagan, the billions year old PhysicalGod got his plans set back by a photographer who didn't even know what she was snapping pictures of.
* In ''FanFic/CardcaptorRad'', the Decepticons plan to [[spoiler:invade the Autobot base]] actually ''works''. They likely would have succeeded in [[spoiler:attaining the Star Saber]] if not for [[spoiler:the humans and mini-cons being there]].
* ''VisualNovel/FateStayNight'''s fanfic ''Fanfic/ChaosTheory'' opens up with this. It introduces the plots and manipulations of all the antagonists of FSN, and then the narrator calmly declares:
--> ''"But mostly? The assorted plans at play here would be going very, very wrong due to the actions of a no-name, no-count, utterly talentless Magus by the name of Shirou Emiya. He had no magic worth mentioning, no combat experience of note, and [[IndyPloy no plan for or knowledge of the War he was about to enter.]] He did, however, have one trait that had derailed a countless number of such grand, far-reaching schemes throughout history.\\
[[SamaritanSyndrome You see, he really, really wanted to be a hero.]]"''
* ''Fanfic/TheChildOfLove'':
** Gendo thought he had planned for any contingence but he did not foresee his son's involvement. Shinji sleeping with Asuka forced him to modify his plans and it ensured that Yui would want to protect his son’s family and Rei would get involved in ways Gendo would not like.
--->'''Fuyutsuki''': But you said that this project was 100% planned, right?\\
'''Gendo''': There was only one mistake on my part. I won't let that happen again.\\
'''Fuyutsuki''': You mean...your son?\\
'''Gendo''': Yes. I didn't think that the Second Child would use the Third to 'satisfy' her boosted hormones...this was a big mistake, and may result in complications.
** In chapter 9 Fuyutsuki warned him that he had not accounted for everyone and someone would stop him, but Gendo did not listen. Cue Rei interfering. And then Yui.
--->'''Fuyutsuki''': I think you're forgetting about someone. Someone who won't forgive you for this, Rokubungi Gendo..."''
* ''Fanfic/ChildrenOfRemnant'': Fifteen years of indoctrination by Salem begins to be undone by Yang deciding to throw the Claimed a party.
* ''Fanfic/TheChoicesOfEarth'': Agent Johnson and the Torchwood team’s other government contacts are completely caught off-guard by the Doctor’s involvement in the situation.
* ''[[https://forums.spacebattles.com/threads/the-chronicles-of-tanya-the-holy-youjo-senki-warcraft.780787/ The Chronicles of Tanya the Holy]]'': Tanya ends up being a massive spanner for not just the Lich King, but for the whole plot of ''[[VideoGame/{{Warcraft}} Warcraft III]]''. First is her actions in Stratholme where she [[spoiler:calls upon Being X and purifies all the infected villagers on top of crippling Mal'Ganis]]. Then in Northrend, Tanya [[spoiler:stops Arthas from taking up Frostmourne and psychically damages the Lich King]]. Besides Arthas never joining the Scourge, the Alliance is reformed, Quel'thalas is never sieged, the Burning Legion doesn't return, and the Horde and Night Elves become trading partners, though the last part doesn't last.[[labelnote:*]]Because Lordaeron never fell, the survivors didn't have to flee to Kalimdor. Without Grom fighting the humans, Thrall never sends him north to Ashenvale, so Grom never incurs the wrath of the Night Elves and Cenarius. Eventually the two factions go to war because the Night Elves refuse to let the Horde harvest enough lumber to support their nation[[/labelnote]]. In the epilogue, it's revealed that Tanya threw things off so much that the Bronze Dragonflight went insane and had to be put down after they started attacking the Alliance in an attempt to set things back on the "correct path".
* In the Mario Fanfic ''Fanfic/ClashOfTheElements'', [[spoiler:Fawful, Alpha and Mario are this to Cackletta's plans. And Bowser too, for freeing the Star Spirits from their imprisonment]].
* ''Fanfic/CodeGeassPaladinsOfVoltron'': C.C. following the Paladins to the Castle of Lions is this for Charles and Marianne, as this puts her beyond the range where the latter can track her.
* Examples in ''Manga/MyHeroAcademia'' fanfic ''Fanfic/ConversationsWithACryptid'':
** Midoriya discussed this with All For One, as he discovers that something must have happened for the murderous supervillain to put his plans on hold. All For One cryptically says that plans can change. [[spoiler:In fact, it was because of his marriage to Inko and Midoriya being born that caused All For One to change his plans so he could stay with them and/or keep them safe.]]
** Another spanner is [[spoiler:the Sludge Villain]] who proceeds to kidnap Midoriya, eventually resulting in [[spoiler:All For One breaking out of prison to rescue his son]].
* ''Fanfic/DeathNoteEquestria'': Mer ends up [[TheStarscream going off Twilight's script]] in order to ruin her in revenge for [[spoiler:Rarity]]'s death as a part of one of Twilight's earlier gambits. [[spoiler:{{Subverted}}, however, as Twilight had actually anticipated this and factored it into her plans, resulting in Twilight's triumph and Mer's death.]]
* ''Fanfic/DevilsDiary'': Before his first outing, Magneto looked into the then-current cadre of heroes and villains and decided neither of them would want or be able to stop his coup. Yet still he was driven away by five heroes who nobody had previously seen before... although he KNEW who they were working for.
-->Damnable adolescent yearlings, every one of them, like the beardless youths Hitler put against the Allies when all his other defenses were cracking. Except these yearlings had power. None of them equal to mine, individually. But they knew how to effectively combine what they had. And they had luck, three times damned three times luck, and NO ONE HAD EVER SEEN THEM BEFORE.\\
All mutants.\\
Three males, one female, and one snow-being whose sex is impossible to determine at this point.\\
An unknown quantity.\\
An x-factor.\\
A XAVIER FACTOR.
* In crossover fanfic ''Fanfic/{{Displaced}}'': Spider-Man's arrival in Gotham City and his meddling with a Joker's heist accidentally causes an unprecedented gang war all across Gotham.
* ''Fanfic/DoingItRightThisTime'': Asuka has grand ambitions to being this after realising she's in a PeggySue situation, but the one to take the biggest direct step towards derailing the Scenario is Rei... and to a lesser extent, the late Naoko Akagi. Shinji still needs some convincing that they can pull it off.
* ''Fanfic/EchoingSilence'': When Celestia banished Twilight, she thought that Twilight was on the verge of going Nightmare, and either would, or be returned to normal by guilt, either of which Celestia had plans to deal with. Unfortunately, the changeling invasion prevented Celestia from looking for Twilight when she wanted to.
* ''Fanfic/EquestriaGirlsAFairlyOddFriendship'':
** Zephyr Breeze is this a couple of times. His streaking causes the Rainbooms to discover Timmy's magic, upending the FOP status quo and starting the plot. Later, he tells Sunset about Timmy being at the skate park after she told him not to go, while he had a magical clone to distract her.
** PlayedForLaughs with Dinkleberg. He obliviously has the Rainbooms' van towed away with them in it, preventing them from discovering Cosmo and Wanda's existence.
* Ironically, Black Wizard Zeref becomes one for one of Grimoire Heart's plans in ''[[https://www.fanfiction.net/s/13153457/1/Fall-of-the-R-System Fall of the R-System]]''. His arrival to destroy the R-System a cult was making distracted and kept Ultear from brainwashing Jellal with a false ghost of Zeref.
* ''Fanfic/FateHaremAntics'': The entire fic is about Irisviel, who is trapped in the Holy Grail but in full control of it, deciding to use the upcoming Holy Grail War to get her son Shirou a harem. All the existing plots and plans promptly get derailed as Iri makes sure all the Masters and Servants besides Shirou are female. Specific examples are:
** Iri's father planned to summon Hercules as a Berserker and force his granddaughter Illya to serve as Master. Iri summoned [[https://typemoon.fandom.com/wiki/Minamoto-no-Raikou Minamoto no Raikou]] instead. Likewise, Iri has some limited ability to speak to her daughter through the Grail, so unlike in canon where Illya hated Shirou and their father (because her grandfather lied to her), Illya knows that their father never abandoned her, and is looking forward to meeting Shirou.
** Bazett tried to summon Cú Chulainn as Lancer, but Iri gave her [[https://typemoon.fandom.com/wiki/Scáthach Scáthach]] instead. More importantly, when Kirei tried to murder Bazett for her Command Seals, Iri briefly stopped his artificial heart, distracting him at a critical moment and ruining the opportunity.
** Sakura summoned [[https://typemoon.fandom.com/wiki/Medusa_(Rider) Medusa]] as Rider, as in canon. Zouken tried to force Sakura to give control over to her brother Shinji, but Iri deliberately made the summoning more explosive than usual, causing the ceiling to fall on Zouken. Sakura and Rider escaped in the confusion.
** After Zouken recovered from having a ceiling drop on him, he summoned a Servant himself, deciding an Assassin would fit him best. Iri gave him [[https://typemoon.fandom.com/wiki/Hassan_of_Serenity Hassan of Serenity,]] a PoisonousPerson. Zouken didn't realize that, slapped her for her perceived disobedience, and [[CruelAndUnusualDeath melted]]. And since Iri had severed his connection to Sakura (which she could only do after Sakura made her contract with the Grail), he couldn't draw power from her and [[OutOfContinues stayed dead for good]].
** Iri did this to herself with Assassin: Since the intent is for Shirou to have sex with all the girls, the fact that she can't touch anyone without killing them is a problem. Iri quickly summons [[https://typemoon.fandom.com/wiki/Mash_Kyrielight Sir Galahad]] as Shielder, who has the power to resist poisons and can pass this onto her allies. And she makes Caren, Kirei's long-lost illegitimate daughter, her Master just to mess with Kirei.
** And Iri ''again'' manages to do this to herself. By summoning Shielder and Ruler, she broke the normal limits on number of Servants and left the door open for others to be summoned. Three separate groups start summoning Servants of their own. Iri can't shut them down, but she can make sure the Servants and Masters are all female. She gives the Ainsworth family [[https://typemoon.fandom.com/wiki/Jeanne_dArc_Alter Jeanne Alter]] as Avenger, but instead of letting Julian become the Master as they intended she grabs his sister Angelica. She gives Fiore of the Yggdmillennia clan [[https://typemoon.fandom.com/wiki/Oda_Nobunaga_(Archer) Oda Nobunaga]] ([[HistoricalGenderFlip who is female in the Nasuverse]]) as Gunner. And Miyu wasn't trying to summon a Servant at all, but didn't understand how the Grail War worked and got [[https://typemoon.fandom.com/wiki/Elizabeth_Báthory Elizabeth Bathory]] as Temptress.
* Nanoha's presence in ''Fanfic/{{Game Theory|LyricalNanoha}}'' derails Precia's carefully laid plans. [[spoiler:But this turns out to be a subversion, because the events that disrupted Precia's original strategy actually made it possible for her to come up with a ''better'' plan that works flawlessly.]]
* ''Fanfic/GuardiansWizardsAndKungFuFighters'':
** During the Battle of Torus Filney, the Rebellion's strategy hits a major stumbling block when [[LizardFolk Simon]] shows up, due to not having planned for his presence. But then they're able to turn the tables on Servantis' forces when they reveal that [[spoiler: [[SuperweaponSurprise they have guns]]]].
** Cedric and Wong's plot to [[TheStarscream betray Phobos]] and steal the Heart of Meridian from him catches [[TheChessmaster Nerissa]] completely off guard, throwing her own plans completely OffTheRails.
* In ''Fanfic/HarryPotterAndTheAlienReality'', Harry represents an unexpected factor to most villains faced by the SGC as none of them are used to facing magic, although SG-1 take care to ensure that Harry doesn’t do anything to expose his magic to the Goa’uld even if the NID are aware of his magic.
* ''Fanfic/HellsisterTrilogy'': During the Apokoliptian War, ComicBook/{{Darkseid}} is always at least three steps ahead of his enemies, and he comes very close to win. His plan only fails because of one factor he couldn't have foreseen: ComicBook/{{Supergirl}} being near from D'reema right when he spoke the Anti-Life Equation. Before succumbing to the Anti-Life Equation, which destroys Free Will, Kara had just enough time to hypnotize D'Reema into speaking the opposite Equation, thus cancelling out its effects.
* ''Fanfic/{{HERZ}}'': SEELE’s attack in 2015 failed because another secret organization accidentally learnt about their plans and interfered with them… something SEELE had not counted on at all.
* ''Fanfic/HigherLearning'': Gendo’s plan started to unravel when [[spoiler:a teacher offered counseling to the Children]].
* ''Fanfic/AHistoryOfMagic'': The Incubators feared that this would happen in the form of an Anomaly, a person who has magical powers not granted by them, for they could awaken the magical powers in ''all'' of humanity. It was why they had arranged for [[spoiler: Jesus to be crucified]], after all. Their fear was eventually realized when Billy Kane used Haitian magic to become a Puer Magi, causing a chain reaction that resulted in thousands of teenagers spontaneously becoming Puer and Puella Magi without contracting.
* ''FanFic/JewelOfDarkness'': The only reason Midnight's plan to [[spoiler:torture Robin to insanity]] fails is because [[spoiler:[[MookLieutenant Ai]] [[TheStarscream betrays her]] on orders from [[GreaterScopeVillain Trigon]]]], something she ''couldn't'' have possibly anticipated.
* In ''Fanfic/{{Kage}}'', Yua predicts [[WesternAnimation/JackieChanAdventures Jade's]] presence in [[{{WesternAnimation/WITCH}} Meridian]] will cause Nerissa's plans to go OffTheRails, and any attempts by the elderly sorceress to force Jade to fit in her plans will only cause the schemes to unravel further. Jade is also this to the second season timeline in general, with the changes already starting to add up.
* ''Fanfic/TheKarmaOfLies'': Both Gabriel and Nathalie plan to use the secret Agreste emergency fund account for their own schemes. Unfortunately for them, Adrien ''also'' knows about said account; it's the only one he's able to access. After he foolishly accesses it right in front of Lila, she memorizes the passwords and secretly cleans him out, leaving just enough money for the checks he wrote to go through.
* ''Fanfic/KaraOfRokyn'': Lex Luthor's plan to kidnap his sister Lena and his nephew fails because his enforcers accidentally stumble on Captain Strong, who looks like a regular old guy but is in fact a vicious, super-strong street brawler. Knowing nothing about him, they underestimate him and are brutally beaten up.
-->Luthor's enforcers had learned to respect superheroes and never take a foe for granted. Chances are, the old guy facing them was tough, a brawler, but they could handle that. They were also three or four to one, depending on how you counted the Siamese twins, Pluto and Plato Statler.\\
The problem was, nobody had ever briefed them on Captain Strong.
* ''Fanfic/KnowThyself'': While Voldemort was a carefully crafted factor in the machine's plans, Harry surviving his encounter with a scar and Voldemort's code being scattered from it was such an anomalous event, agents had been keeping a close an eye on him to ensure that he wasn't a threat up until the point that Trinity found him. Not only that, but the machines didn't even notice his absence at first because he is the only wizard to have been successfully unplugged, all other attempts rendered in a vegetative state.
* The ''Manga/FairyTail'' AU fic ''[[http://www.fanfiction.net/s/4711916/1/Lost-Magic Lost Magic]]'' is an interesting example. While the deliberate wrench in Jellal's plans is Simon, the one whose mistake actually set his plot derailing was [[{{Irony}} Jellal, himself]]. [[ItMakesSenseInContext By accidentally getting himself pregnant with Erza's child.]]
* ''Fanfic/NedStarkLives'' reveals that Jaqen H'ghar had been hired by [[spoiler:the Great Other]] to kill [[spoiler:Jon]]. Arya's presence in the Night's Watch caravan completely derailed that plan, though.
* ''Fanfic/NewBeginningsSmallville'': After being exposed, Clark intends to go back a few days in order to discredit Linda Lake's before she can out him. Linda's interference, though, causes him and Lois to travel all the way back to 2001.
* ''FanFic/QueenOfAllOni'': Jade's otherwise flawless [[OperationBlank Operation: Steel Lightning]] only fails because of the presence of Agent Wisker, who she didn't know and couldn't plan for. He doesn't stop her, but slows her down long enough for Uncle to catch up with her and beat her.
* ''Fanfic/{{Quicken}}'': [[AntiHero Emma]] accidentally and inadvertently causes a gang war only because she was in the wrong place in the wrong time wearing the wrong clothes.
* The ''FanFic/PonyPOVSeries'' has one that's notable for the exceptionally long time required for the spanner to actually get into the villain's works. [[spoiler:Back in the G3 Universe, which was facing TheEndOfTheWorldAsWeKnowIt (actually a ShootTheDog to avert a Class Z Apocalypse) at the time, Pinkie Pie's best friend Minty just bled to death after their fight with Luna, leaving behind her "spirit" (or at least a piece of herself). Strife, Discord's sister and Spirit of Natural Selection, is fighting the survivors of the doomed world (in order to give them at least the chance to fight for their survival, something she believes is the right of all living things) and sent Heartless-like spirits of "erased" ponies after them. One of these falls into the canyon where Pinkie and Minty's fight took place, wounded in battle. Pinkie, in a split second choice, fuses the piece of Minty with the shadow, which turns out to be that of the G1 Twilight. The result? ''[[TheHero Twilight Sparkle!]]'']]
** During the [[BadFuture Dark World Arc]], [[spoiler:Discord's little sister Rancor is this. She arrives to get close to Discord and ultimately steal back Destruction's power from him so it can be used for its intended purpose (Destruction's original job as an AnthropomorphicPersonification), mortally wounding him in the process. This ends up throwing a gigantic wrench in Nightmare Eclipse/Paradox's plans, allowing Discord to {{Out Gambit|ted}} her and alert Twilight to the [[GroundhogDayLoop true nature]] [[IronicHell of the Dark World]], forcing Paradox to expose herself to the heroes. The name Rancor chooses after succeeding (Disruption) couldn't be more appropriate. It's this trope especially because, while its implied she knew Paradox was there, she didn't care one way or the other what happened so long as her own mission was a success]].
** Part 6 of Shining Armor's Arc has Sergeant Thunderchild be this [[BigBad General-Admiral Makarov]]'s attempt to kill Shining Armor. Makarov ''[[WhoAreYou didn't even know his name]]'', yet he shows up [[BigDamnHeroes just in time]] to break through Makarov's AntiMagic field and save Shining. This also buys time for more Shining's forces to show up in a GunshipRescue and drive Makarov's forces off.
** During the Wedding Arc, Prince Blueblood inadvertently foils Queen Chrysalis' plan just because he wanted to take a girl on a date. [[spoiler:He led his date through the caves under Canterlot, and ended up finding the imprisoned Princess Cadance.]]
* In Evangelion fan-fic ''Manga/ReTake'', SEELE finds all their plans foiled by something they could never have anticipated [[spoiler: Shinji be aided by [[ItMakesSenseInContext Ghost-Asuka and "God"]] which allows him to destroy the Mass Production Evas during the fan-fic's take the events of "End"]].
* In ''Franchise/TheMatrix'' fic ''[[https://www.fanfiction.net/s/2086636/1/Rescue-Run Rescue Run]]'', Captain Dena Reese unknowingly serves as this to the Machines' cycle of control to keep the human population of Earth under their control; not only does she confirm that the Matrix has existed for longer than the two centuries the people of Zion believed, but she also helps them make contact with the human colonies in the rest of the solar system. Through her presence, [[spoiler:the people of Zion are evacuated from Earth and relocated to a new green planet, while the spacefleet destroys the Machine mainframe and the Matrix to prevent the machines following them into space]].
* The escape sequence in ''[[https://www.fanfiction.net/s/8960878/49/Revan-s-Story Revan's Story]]'' is a series of spanners caught in other spanners. Like in canon, the protagonists anticipate capture by the ship ''Leviathan'', so they each come up with a plan to escape and free the others. Unlike in canon, Darth Bandon throws a wrench in their plans. First, he stops HK and T-3's plans because [[spoiler:he recognizes Revan's personal assassination droid]], and orders his troops to wipe their memories and physically restrain them in case the wipe doesn't go deep enough. Second, he stops Jolee's plan to JediMindTrick the guard into solitary confinement because he knows what the trick looks like. Third, he senses Juhani sneaking through the Force and overpowers her. Canderous's plan of faking his death is eliminated for being risky, and Zaalbar is absent. [[spoiler:Only Mission's plan goes undetected by virtue of not starting until she's away from Bandon, and even then she's almost caught. The party isn't recaptured because Admiral Karath, the last spanner, was also TheMole]].
* In "[[https://archiveofourown.org/works/23791732 Spidey-Team]]", Peter Parker of the Franchise/MarvelCinematicUniverse has been part of the [[WesternAnimation/SpiderManIntoTheSpiderVerse Spider-Verse crossover]], with the result that he is already aware of the multiverse before he meets Beck and thus knows that Beck can't be a dimensional traveller as he doesn't know anything about the rules (such as how Beck "should" be glitching if he's been in another dimension for two weeks).
* ''Fanfic/SpiderX'': Mystique’s immediate plan to spend time with Rogue as Risty and her and Magneto's more long-term plan to infiltrate the manor and pose as Xavier are both thwarted just because Peter Parker joins the X-Men, as his spider-sense makes him aware of Mystique's true identity even when she isn’t explicitly doing anything dangerous (although she doesn't actually know how he sensed her for some time).
* ''Fanfic/Team8'': In Chapter 17, Kurenai tells Manga/{{Naruto}} to use his chakra pulse to dispel the genjutsu Kabuto put on the stadium. Naruto overpowers the pulse so much it ends up covering the entire village -- causing Orochimaru's plan to fall to pieces twice over, as not only did it dispel the jutsu that were going to summon the giant snakes, it also destroys the barrier he had put to prevent people from interfering with his duel with the Third Hokage.
* In [[http://roosterteeth.com/user/CornOwl/albums/17723 this]] ''WebVideo/TenLittleRoosters'' fancomic series, every one of [[spoiler:Barbara]]'s attempts (and traps) to murder their Rooster Teeth colleagues [[HilarityEnsues is foiled due to the others' sheer dumb luck (with a few cases of taking a level in intelligence).]] The result? [[EveryoneLives Everyone ends up surviving]]:
** [[spoiler:Michael's poisoned glass]] breaks before they have a chance to [[spoiler:drink from it]].
** [[spoiler:Gavin and his clone]] manage to catch themselves, preventing them from [[spoiler:falling in the mousetraps]].
** ''None'' of [[spoiler:the arrows]] wind up hitting [[spoiler:Chris]].
** When reaching for the extra gun, [[spoiler:Burnie]] spots [[spoiler:the scorpion]] and shoots it.
** [[spoiler Gus]] slams the door on the Killer.
** [[spoiler:Adam]] trips over a cord just as [[spoiler:the Killer is about to strangle them]].
** [[spoiler:The puma]] decides they're more interested in being [[spoiler:petted by Lindsay]] than [[spoiler:mauling her to death]].
** The part of [[spoiler:the treadmill]] that [[spoiler:Miles is glued to]] ''breaks off completely''.
* ''FanFic/ThisBites'':
** The Unluckies. If the ForWantOfANail in Chapter 19 wasn't enough, in Chapter 20, Cross attempts to use Soundbite's powers to stop or stall the Rebel Army outside of Alubarna. Unfortunately, the Unluckies arrive and snatch the snail, scrapping that plan. And even after they're beaten, Miss Friday manages to disable Soundbite's powers until Luffy beats Crocodile.
*** For a while, it actually became something of a RunningGag that the Straw Hats' plans never worked out as planned, to the point that the characters started making note of in their planning sessions. This was particularly frustrating and humiliating for Cross, as he is the official tactician for the crew. But starting after Skypiea, things start going much better.
** Granny Kokoro proves to be this to Cross's plans. Sloshed out of her mind, she browbeats Iceburg and Franky into feeling the love that the Going Merry has for her crew, and encouraging them, as Tom's apprentices, construct a ship worthy of the Oro Jackson's successor... ''within earshot of Iceburg's secretary and one of his best shipwrights''.
** Aokiji. Post-Enies Lobby, when he came across an island hosting a big pirate brawl, he decided to halt the whole thing with an Ice Age... [[spoiler: giving Blackbeard the perfect opportunity to swallow up his now-frozen opponents.]]
* In ''FanFic/UltimateSleepwalker: The New Dreams'', the Green Goblin kidnapped and planned to publicly murder Gwen Stacy as a way to get revenge on her father, Captain George Stacy of the NYPD. While Franchise/SpiderMan intervened and tried to rescue Gwen, the Goblin had anticipated that and set things up so he'd be able to kill both Spider-Man and Gwen at the same time. Unfortunately, what he ''didn't'' take into account was Sleepwalker following Spider-Man to the [[ShoutOut top of the bridge]] a Cascnd distracting him long enough for Spider-Man to rescue Gwen and get her to safety. The Goblin proceeded to have a VillainousBreakdown.
* In ''Fanfic/TheVow'' (an AlternateUniverseFic of ''WesternAnimation/KungFuPanda2''), when Po and the Furious Five have been imprisoned in the dungeon of the Tower of the Sacred Flame and Shen prepares to spring his trap for the invited nobility of China, Lianne sends [[NinjaMaid Jade]] to free the heroes before they can be killed, allowing them to rescue the nobility, setting back Shen's plans of conquest a little.
* Harmony acts as one in ''[[http://www.tthfanfic.org/Story-20251-18/cmdruhura+We+re+Doomed.htm We're Doomed]]'' to Marcie Ross and her plans to murder the popular kids as revenge. Namely, when Cordelia is running from the invisible monster trying to kill her, she runs right in front of Harmony's car who swerves to avoid her, right into Marcie. Harmony also ruins the plans of the organization seeking to recruit Marcie.
* Xander in ''[[https://www.tthfanfic.org/Story-28404-1/DianeCastle%2bXendra.htm Xendra]]'' functions as a spanner on a cosmic scale. Not only can Drusilla the Mad Seer not See him and thus can't counter his plans, but he's shown to be immune to prophecy, leading to him breaking three or four prophecies, including Jasmine's plan to be reborn via Cordelia.
* ''Fanfic/ZumasFear'': [[spoiler:Believe it or not, Zuma ends up screwing Stone’s EvilPlan after the death of his family.]]
* In the ''Franchise/{{Danganronpa}}'' AU, ''[[https://www.fanfiction.net/s/13869977/1/Despair-Arc-Execution-Failed Despair Arc: Execution Failed?]]'', Kyoko and Makoto ruin Junko's plan before it even gets off the ground, as Kyoko's investigation leads her and an accompanying Makoto to discover a [[spoiler:still alive Chiaki before she succumbs to her gruesome wounds. This, in turn, leads to not only 77-B being snapped out of Junko's influence, but Izuru returning to being Hajime.]]
[[/folder]]

** In the third case of ''Justice For All'', [[spoiler:Acro's plan to murder Regina was to call her to a specific point where he would drop a heavy weight on her head. Problem is, the note he secretly planted on Regina began with "To the murderer...". Due to Regina being very naive, she didn't think the note was for her, and posted it on the circus's bulletin board, where her father saw it and responded to it in Regina's place]]. Then you realize that [[spoiler:Acro wanted to kill her because her naivete led to his brother being put into a coma, [[WhatAnIdiot and he should have known that she would never realize the note was meant for her]]..]].

** In the final case of ''VisualNovel/AceAttorneyInvestigations'', the shenanigans of [[spoiler: Larry Butz and Wendy Oldbag, of all people]] end up helping Miles Edgeworth put away the seemingly untouchable BigBad. [[spoiler:Larry, by accidentally breaking the Samurai Spear, forces the staff to have the Steel Samurai use a different move instead, thus enabling Edgeworth to realize that Alba was not at the Steel Samurai show while he was killing Manny Coachen. Wendy Oldbag takes the box of "Rising Sun Dogs," which turns out to have a drop of Alba's blood on it, and combined with Alba's wound, proves that he was injured while killing Coachen]].

** In ''VisualNovel/DanganronpaTriggerHappyHavoc'', the entire triumph of hope over despair on Earth hinges on a poorly-fitting bathroom door that gets stuck in the doorframe. A door which, because of Naegi's Ultimate-level luck (which manifests as [[UnluckilyLucky seemingly-bad luck that turns out to be good luck in disguise]]), gives him an alibi for a crime he would otherwise have been framed and executed for. [[MessianicArchetype Given how important Naegi would go on to be to the future of humanity]], it's no exaggeration to say that ''that'' was the moment that [[spoiler: Junko's]] fate was well and truly sealed. Even worse, it's implied that [[spoiler: she]] deliberately ''gave'' him the crappy door just because [[ItAmusedMe the idea of the Ultimate Lucky Student being the only one with a crappy door was funny]].
** Naegi's luck is referred to as a "spanner in the works" verbatim by [[spoiler: Junko]]; no matter how CrazyPrepared [[spoiler: she]] is for every possible scenario, Naegi's luck is totally unpredictable and can throw everything off on a dime, which is why [[spoiler: she's]] captivated by him.

Whether it's TheDitz, TheFool, InspectorOblivious, or a [[EverythingsBetterWithMonkeys monkey]] [[labelnote:Geddit?]][[DontExplainTheJoke Because another word for "spanner" is "monkey wrench"]], and having a literal monkey ruin your plans is a StealthPun[[/labelnote]], the Spanner in the Works is the miscreant capable of derailing the most ironclad of [[ThePlan plans]] by [[AchievementsInIgnorance unknowingly]] [[TakeAThirdOption taking an option that the planner hadn't even considered]]. They ruin the implausible {{Gambit Roulette}}s by [[FlawExploitation exploiting their one, intrinsic flaw:]] their reliance on {{Contrived Coincidence}}s, [[ClockKing rigid patterns]], and the assumption that nobody would be stupid enough to actually push the BigRedButton or [[TooDumbToLive fight the apparently]] [[NighInvulnerability unstoppable robot.]]

The trope is reputedly named for the [[OlderThanRadio Industrial Revolution]]-era practice of disgruntled workers throwing a spanner into a machine, either because of fears that [[JobStealingRobot machines would put them]] [[LuddWasRight out of work]], or as a bargaining chip for better working conditions (and often because they were the only ones who knew how to repair the machines as well).

Disgruntled French workers did this by throwing ''sabots'' (wooden-soled clogs) into machinery -- giving us the word '''sabotage'''.

%% This page has been alphabetized. Please add new examples in the correct order.

(Note for Americans reading this: "Spanner" is the British English word for what you would call a "wrench", with the added benefit of it being slang for a stupid person. It has nothing to do with a {{Long Runner|s}} in development. The equivalent American phrase specifically involves a ''monkey'' wrench, known in the UK as a gas grip — "He really threw a monkey wrench into my plans.")

Disgruntled French workers did this by throwing ''sabots'' (wooden-soled clogs) into machinery — giving us the word '''sabotage'''.

* ''Fanfic/AndTheGiantAwoke'': When Euron and Tywin make their plans for dealing with each other - raid into the other's lands to force the enemy to retreat and fight in their own terms - all of them are for nothing when a storm forces both fleets to change course and they meet in the middle of the sea.

* ''Fanfic/Team8'': In Chapter 17, Kurenai tells Manga/{{Naruto}} to use his chakra pulse to dispel the genjutsu Kabuto put on the stadium. Naruto overpowers the pulse so much it ends up covering the entire village - causing Orochimaru's plan to fall to pieces twice over, as not only did it dispel the jutsu that were going to summon the giant snakes, it also destroys the barrier he had put to prevent people from interfering with his duel with the Third Hokage.

** ...referencing a peculiar event--long forgotten by most, perhaps--though the unlikelihood of [[http://news.bbc.co.uk/onthisday/hi/dates/stories/july/9/newsid_2498000/2498731.stm Michael Fagin's misadventure]] conveys this trope's inherent flavor of the unexpected. In the BBC's retrospective, we learn "[t]he Queen was only able to raise the alarm when he asked for a cigarette." In more security-conscious days, who'd imagine such a Royal [[FishOutOfWater contretemps]] could occur at all?

* ''Webcomic/ElGoonishShive'': Sirleck's plans were carefully calculated, but he never anticipated that Ellen would be conscious whilst he puppeteered her body - which gave Magus the time he needed to dispose of him.

* ''Webcomic/SchlockMercenary'': In Book 15 Schlock ends up derailing a StagedPopulistUprising simply by drawing the attention of a police officer [[spoiler:who was unwittingly carrying a bomb that was supposed to blow up the heads of the popularly elected legislature, providing the pretext for the fake revolt]]. [[spoiler:And there was a second spanner- most of the police force was supposed to have their personalities overwritten as part of the uprising, it just that one of them was hijacked by a ''different'' party.]]

** [[ConvictionByCounterfactualClue A simple lack of knowledge]] led him to believe (and say) that human coins were forged. A politician's OhCrap moment led a guard to realize [[RightForTheWrongReasons they were indeed fakes]]--and who was behind it.
** His very decision to become a Questor--paired with the discovery of an old contract--puts his home village in peril. The contract stated that the previous Questor was to retrieve some artifacts in exchange for land on which to build a village. The problem: the old Questor failed to do so, and now that there's a new Questor, a political faction intends to use that contract to get Freeman Downs repossessed and thus out of the picture. Quentyn's decision? Retrieve those artifacts, knowing that if he dies in the attempt, the law ensures that the contract ends with him. He knows nothing about the true scheme at work, and the opposing faction has no idea what to do now. The legal counsel sent to deliver the bad news summed this trope up rather perfectly:

** His desire to help a human village ended with him in a position to UTTERLY screw over a fae--[[GoodIsNotNice which he does]] so very EPICALLY. [[spoiler: The fae in question calls a [[TheWildHunt Wild Hunt]] on Quentyn, promising a wish if he survives. Quentyn barely manages to win, but it's now when the fae realizes to his horror that Quentyn is not only part of a race that's protected from the Hunt, but also under the protection of another being which doubly prohibits him. As punishment, the amount of wishes that the fae is supposed to give is tripled. The first two wishes are used to deprive him of everything he has. The third wish is a traditional "leave without taking revenge" wish...with an additional clause that forbids him from ever calling a hunt on that plane again.]]

** "Jack's Heist" gets hit because of the escape jet they were using - they couldn't escape cleanly in traffic and later [[spoiler:roasts Michael, who had the money.]]

(Note for Americans reading this: "Spanner" is the Queen's English word for what you would call a "wrench", with the added benefit of it being slang for a stupid person. It has nothing to do with a {{Long Runner|s}} in development. The equivalent American phrase specifically involves a ''monkey'' wrench, known in the UK as a gas grip — "He really threw a monkey wrench into my plans.")

** Zephyr Breeze is this a couple of times. His streaking causes the Rainbooms to discover Timmy's magic, upending the FOP status quo and starting the plot. Later, he tells Sunset about Timmy being at the skate park after she told him not to go, while he had a magical clone to distract her.her.

* In the ''WebAnimation/HomestarRunner'' holiday toon [[http://www.homestarrunner.com/xmas08.html "A Death-Defying Decemberween,"]] Homestar announces to one and all that he's going to sled down the Steep Deep -- a ''vertical cliff face'' -- and Strong Bad catches The Cheat surreptitiously helping Homestar bury a mattress at the foot of the alleged slope. Of course, Strong Bad being Strong Bad, he moves the mattress expecting Homestar to maim himself on impact...but the next day, when Homestar sleds down the Steep Deep, he makes a perfect landing. As it turned out, the mattress was full of "hammers, broken glass and candy canes sucked down 'til they're all pointy"; the whole thing was a ridiculously elaborate (and painful) scheme for Homestar to get out of having to spend Christmas with his girlfriend [[GranolaGirl Marzipan's]] parents, one that Strong Bad successfully sabotaged (even if the end result wasn't ''quite'' what he had been expecting).

** During the Wedding Arc, Prince Blueblood inadvertently foils Queen Chrysalis' plan just because he wanted to take a girl on a date. [[spoiler:He lead his date through the caves under Canterlot, and ended up finding the imprisoned Princess Cadance.]]

* The escape sequence in ''[[https://www.fanfiction.net/s/8960878/49/Revan-s-Story Revan's Story]]'' is a series of spanners caught in other spanners. Like in canon, the protagonists anticipate capture by the ship ''Leviathan'', so they each come up with a plan to escape and free the others. Unlike in canon, Darth Bandon throws a wrench in their plans. First, he stops HK and T-3's plans because [[spoiler:he recognizes Revan's personal assassination droid]], and orders his troops to wipe their memories and physically restrain them in case the wipe doesn't go deep enough. Second, he stops Jolee's plan to JediMindTrick the guard into solitary confinement because he knows what the trick looks like. Third, he senses Juhani sneaking through the Force and overpowers her. Canderous's plan of faking his death is eliminated for being risky, and Zaalbar is absent. [[spoiler:Only Mission's plan goes undetected by virtue of not starting until she's away from Bandon, and even then she's almost caught. The party isn't recaptured because Admiral Karath, the last spanner, was also TheMole]].
* ''Fanfic/{{Atonement}}'': The Slaughterhouse Nine might have gotten a new member in Ruin had Mnemosyne not interfered, turned Burnscar against the rest of the Nine, and freed Hunter.
* ''Fanfic/KaraOfRokyn'': Lex Luthor's plan to kidnap his sister Lena and his nephew fails because his enforcers accidentally stumble on Captain Strong, who looks like a regular old guy but is in fact a vicious, super-strong street brawler. Knowing nothing about him, they underestimate him and are brutally beaten up.
-->Luthor's enforcers had learned to respect superheroes and never take a foe for granted. Chances are, the old guy facing them was tough, a brawler, but they could handle that. They were also three or four to one, depending on how you counted the Siamese twins, Pluto and Plato Statler.\\
The problem was, nobody had ever briefed them on Captain Strong.
* ''Fanfic/AndTheGiantAwoke'': When Euron and Tywin make their plans for dealing with each other - raid into the other's lands to force the enemy to retreat and fight in their own terms - all of them are for nothing when a storm forces both fleets to change course and they meet in the middle of the sea.
* ''Fanfic/AvatarTheLastAlicorn'': Sweetie's plan to take over Fillydelphia and eliminate all the water and fire benders along with the avatar and the great dragon would've gone perfectly, if it wasn't for AJ learning metal-bending, allowing her to escape, and provide Team Avatar an avenue to escape.
* ''Fanfic/KnowThyself'': While Voldemort was a carefully crafted factor in the machine's plans, Harry surviving his encounter with a scar and Voldemort's code being scattered from it was such an anomalous event, agents had been keeping a close an eye on him to ensure that he wasn't a threat up until the point that Trinity found him. Not only that, but the machines didn't even notice his absence at first because he is the only wizard to have been successfully unplugged, all other attempts rendered in a vegetative state.
* ''[[https://forums.spacebattles.com/threads/the-chronicles-of-tanya-the-holy-youjo-senki-warcraft.780787/ The Chronicles of Tanya the Holy]]'': Tanya ends up being a massive spanner for not just the Lich King, but for the whole plot of ''[[VideoGame/{{Warcraft}} Warcraft III]]''. First is her actions in Stratholme where she [[spoiler:calls upon Being X and purifies all the infected villagers on top of crippling Mal'Ganis]]. Then in Northrend, Tanya [[spoiler:stops Arthas from taking up Frostmourne and psychically damages the Lich King]]. Besides Arthas never joining the Scourge, the Alliance is reformed, Quel'thalas is never sieged, the Burning Legion doesn't return, and the Horde and Night Elves become trading partners, though the last part doesn't last.[[labelnote:*]]Because Lordaeron never fell, the survivors didn't have to flee to Kalimdor. Without Grom fighting the humans, Thrall never sends him north to Ashenvale, so Grom never incurs the wrath of the Night Elves and Cenarius. Eventually the two factions go to war because the Night Elves refuse to let the Horde harvest enough lumber to support their nation[[/labelnote]]. In the epilogue, it's revealed that Tanya threw things off so much that the Bronze Dragonflight went insane and had to be put down after they started attacking the Alliance in an attempt to set things back on the "correct path".
* ''Fanfic/EchoingSilence'': When Celestia banished Twilight, she thought that Twilight was on the verge of going Nightmare, and either would, or be returned to normal by guilt, either of which Celestia had plans to deal with. Unfortunately, the changeling invasion prevented Celestia from looking for Twilight when she wanted to.
* In crossover fanfic ''Fanfic/{{Displaced}}'': Spider-Man's arrival in Gotham City and his meddling with a Joker's heist accidentally causes an unprecedented gang war all across Gotham.
* Ironically, Black Wizard Zeref becomes one for one of Grimoire Heart's plans in [[https://www.fanfiction.net/s/13153457/1/Fall-of-the-R-System Fall of the R-System]]. His arrival to destroy the R-System a cult was making distracted and kept Ultear from brainwashing Jellal with a false ghost of Zeref.
* ''Fanfic/NewBeginningsSmallville'': After being exposed, Clark intends to go back a few days in order to discredit Linda Lake's before she can out him. Linda's interference, though, causes him and Lois to travel all the way back to 2001.

* ''VisualNovel/FateStayNight'''s fanfic ''Fanfic/ChaosTheory'' opens up with this. It introduces the plots and manipulations of all the antagonists of FSN, and then the narrator calmly declares:
--> ''"But mostly? The assorted plans at play here would be going very, very wrong due to the actions of a no-name, no-count, utterly talentless Magus by the name of Shirou Emiya. He had no magic worth mentioning, no combat experience of note, and [[IndyPloy no plan for or knowledge of the War he was about to enter.]] He did, however, have one trait that had derailed a countless number of such grand, far-reaching schemes throughout history.\\
[[SamaritanSyndrome You see, he really, really wanted to be a hero.]]"''

* In ''FanFic/UltimateSleepwalker: The New Dreams'', the Green Goblin kidnapped and planned to publicly murder Gwen Stacy as a way to get revenge on her father, Captain George Stacy of the NYPD. While Franchise/SpiderMan intervened and tried to rescue Gwen, the Goblin had anticipated that and set things up so he'd be able to kill both Spider-Man and Gwen at the same time. Unfortunately, what he ''didn't'' take into account was Sleepwalker following Spider-Man to the [[ShoutOut top of the bridge]] a Cascnd distracting him long enough for Spider-Man to rescue Gwen and get her to safety. The Goblin proceeded to have a VillainousBreakdown.
* In ''Franchise/TheMatrix'' fic ''[[https://www.fanfiction.net/s/2086636/1/Rescue-Run Rescue Run]]'', Captain Dena Reese unknowingly serves as this to the Machines' cycle of control to keep the human population of Earth under their control; not only does she confirm that the Matrix has existed for longer than the two centuries the people of Zion believed, but she also helps them make contact with the human colonies in the rest of the solar system. Through her presence, [[spoiler:the people of Zion are evacuated from Earth and relocated to a new green planet, while the spacefleet destroys the Machine mainframe and the Matrix to prevent the machines following them into space]].
* In ''Fanfic/HarryPotterAndTheAlienReality'', Harry represents an unexpected factor to most villains faced by the SGC as none of them are used to facing magic, although SG-1 take care to ensure that Harry doesn’t do anything to expose his magic to the Goa’uld even if the NID are aware of his magic.
* ''Fanfic/SpiderX'': Mystique’s immediate plan to spend time with Rogue as Risty and her and Magneto's more long-term plan to infiltrate the manor and pose as Xavier are both thwarted just because Peter Parker joins the X-Men, as his spider-sense makes him aware of Mystique's true identity even when she isn’t explicitly doing anything dangerous (although she doesn't actually know how he sensed her for some time).
* The ''FanFic/PonyPOVSeries'' has one that's notable for the exceptionally long time required for the spanner to actually get into the villain's works. [[spoiler:Back in the G3 Universe, which was facing TheEndOfTheWorldAsWeKnowIt (actually a ShootTheDog to avert a Class Z Apocalypse) at the time, Pinkie Pie's best friend Minty just bled to death after their fight with Luna, leaving behind her "spirit" (or at least a piece of herself). Strife, Discord's sister and Spirit of Natural Selection, is fighting the survivors of the doomed world (in order to give them at least the chance to fight for their survival, something she believes is the right of all living things) and sent Heartless-like spirits of "erased" ponies after them. One of these falls into the canyon where Pinkie and Minty's fight took place, wounded in battle. Pinkie, in a split second choice, fuses the piece of Minty with the shadow, which turns out to be that of the G1 Twilight. The result? ''[[TheHero Twilight Sparkle!]]'']]
** During the [[BadFuture Dark World Arc]], [[spoiler:Discord's little sister Rancor is this. She arrives to get close to Discord and ultimately steal back Destruction's power from him so it can be used for its intended purpose (Destruction's original job as an AnthropomorphicPersonification), mortally wounding him in the process. This ends up throwing a gigantic wrench in Nightmare Eclipse/Paradox's plans, allowing Discord to {{Out Gambit|ted}} her and alert Twilight to the [[GroundhogDayLoop true nature]] [[IronicHell of the Dark World]], forcing Paradox to expose herself to the heroes. The name Rancor chooses after succeeding (Disruption) couldn't be more appropriate. It's this trope especially because, while its implied she knew Paradox was there, she didn't care one way or the other what happened so long as her own mission was a success]].
** Part 6 of Shining Armor's Arc has Sergeant Thunderchild be this [[BigBad General-Admiral Makarov]]'s attempt to kill Shining Armor. Makarov ''[[WhoAreYou didn't even know his name]]'', yet he shows up [[BigDamnHeroes just in time]] to break through Makarov's AntiMagic field and save Shining. This also buys time for more Shining's forces to show up in a GunshipRescue and drive Makarov's forces off.
** During the Wedding Arc, Prince Blueblood inadvertently foils Queen Chrysalis' plan just because he wanted to take a girl on a date. [[spoiler:He lead his date through the caves under Canterlot, and ended up finding the imprisoned Princess Cadance.]]
* In Evangelion fan-fic ''Manga/ReTake'', SEELE finds all their plans foiled by something they could never have anticipated [[spoiler: Shinji be aided by [[ItMakesSenseInContext Ghost-Asuka and "God"]] which allows him to destroy the Mass Production Evas during the fan-fic's take the events of "End"]].
* In the Mario Fan-Fic ''FanFic/ClashOfTheElements'', [[spoiler: Fawful, Alpha and Mario are this to Cackletta's plans. And Bowser too, for freeing the Star Spirits from their imprisonment]].
* Nanoha's presence in ''Fanfic/{{Game Theory|LyricalNanoha}}'' derails Precia's carefully laid plans. [[spoiler:But this turns out to be a subversion, because the events that disrupted Precia's original strategy actually made it possible for her to come up with a ''better'' plan that works flawlessly.]]
* The ''Manga/FairyTail'' AU fic ''[[http://www.fanfiction.net/s/4711916/1/Lost-Magic Lost Magic]]'' is an interesting example. While the deliberate wrench in Jellal's plans is Simon, the one whose mistake actually set his plot derailing was [[{{Irony}} Jellal, himself]]. [[ItMakesSenseInContext By accidentally getting himself pregnant with Erza's child.]]

* ''FanFic/QueenOfAllOni'': Jade's otherwise flawless [[OperationBlank Operation: Steel Lightning]] only fails because of the presence of Agent Wisker, who she didn't know and couldn't plan for. He doesn't stop her, but slows her down long enough for Uncle to catch up with her and beat her.

* ''FanFic/AnAlternateKeitaroUrashima'' repeatedly derails his grandmother's attempts to manipulate him simply by letting others know how [[ManipulativeBitch manipulative]] she is. As a result, when she shows up and starts spinning her webs, she winds up proving him right.
** Mokoto also runs afoul of this when she threatens Keitaro one time too many. When she draws her katana, she's unaware that [[spoiler:some police officers are passing behind her and witness it]].
* ''Fanfic/DeathNoteEquestria'': Mer ends up [[TheStarscream going off Twilight's script]] in order to ruin her in revenge for [[spoiler:Rarity]]'s death as a part of one of Twilight's earlier gambits. [[spoiler: Subverted, however, as Twilight had actually anticipated this and factored it into her plans, resulting in Twilight's triumph and Mer's death.]]

* ''Fanfic/AHistoryOfMagic'': The Incubators feared that this would happen in the form of an Anomaly, a person who has magical powers not granted by them, for they could awaken the magical powers in ''all'' of humanity. It was why they had arranged for [[spoiler: Jesus to be crucified]], after all. Their fear was eventually realized when Billy Kane used Haitian magic to become a Puer Magi, causing a chain reaction that resulted in thousands of teenagers spontaneously becoming Puer and Puella Magi without contracting.
* In ''Fanfic/TheVow'' (an AlternateUniverseFic of ''WesternAnimation/KungFuPanda2''), when Po and the Furious Five have been imprisoned in the dungeon of the Tower of the Sacred Flame and Shen prepares to spring his trap for the invited nobility of China, Lianne sends [[NinjaMaid Jade]] to free the heroes before they can be killed, allowing them to rescue the nobility, setting back Shen's plans of conquest a little.
* Harmony acts as one in ''[[http://www.tthfanfic.org/Story-20251-18/cmdruhura+We+re+Doomed.htm We're Doomed]]'' to Marcie Ross and her plans to murder the popular kids as revenge. Namely, when Cordelia is running from the invisible monster trying to kill her, she runs right in front of Harmony's car who swerves to avoid her, right into Marcie. Harmony also ruins the plans of the organization seeking to recruit Marcie.
* ''FanFic/TheBridge'' gives a borderline humorous example in an otherwise completely serious situation. [[BigBad Bagan]] has set up an elaborate XanatosGambit that would work out in full to both secure more power for himself as well as kill [[BigGood Harmony]]. A crux of it was keeping a displaced Monster X separated from his comrades and put into the Equestria Girls world, where he'll be weaker in his human form and thus easier to kill by Bagan's agent, Enjin. One bystander messed it up and they weren't another kaiju nor an Equestrian hero intervening in the fight. EG!Photo Finish happened to be at the scene of a battle between X and Enjin at a hospital and took some pictures, thinking it was a movie stunt being filmed. Days later when an ally of X was in the same realm but dozens of miles away, she bumped into Photo, saw the pictures and recognized X in the images; and was able to alert her allies that she'd found him and he was in trouble. Bagan, the billions year old PhysicalGod got his plans set back by a photographer who didn't even know what she was snapping pictures of.

* ''Fanfic/AdviceAndTrust'': Shinji and Asuka end up ruining Gendo's plans by [[DefusingTheTykeBomb befriending Rei]], although this happens long before his plans are put into action. And ''everyone'' is completely unaware of the implication of this, meaning that they spend several chapters trying to figure out how to stop him, and he still thinks that he's in control of the situation, despite the fact that he's already lost.
* ''FanFic/ThisBites'':
** The Unluckies. If the ForWantOfANail in Chapter 19 wasn't enough, in Chapter 20, Cross attempts to use Soundbite's powers to stop or stall the Rebel Army outside of Alubarna. Unfortunately, the Unluckies arrive and snatch the snail, scrapping that plan. And even after they're beaten, Miss Friday manages to disable Soundbite's powers until Luffy beats Crocodile.
*** For a while, it actually became something of a RunningGag that the Straw Hats' plans never worked out as planned, to the point that the characters started making note of in their planning sessions. This was particularly frustrating and humiliating for Cross, as he is the official tactician for the crew. But starting after Skypiea, things start going much better.
** Granny Kokoro proves to be this to Cross's plans. Sloshed out of her mind, she browbeats Iceburg and Franky into feeling the love that the Going Merry has for her crew, and encouraging them, as Tom's apprentices, construct a ship worthy of the Oro Jackson's successor... ''within earshot of Iceburg's secretary and one of his best shipwrights''.
** Aokiji. Post-Enies Lobby, when he came across an island hosting a big pirate brawl, he decided to halt the whole thing with an Ice Age... [[spoiler: giving Blackbeard the perfect opportunity to swallow up his now-frozen opponents.]]
* Xander in ''[[https://www.tthfanfic.org/Story-28404-1/DianeCastle%2bXendra.htm Xendra]]'' functions as a spanner on a cosmic scale. Not only can Drusilla the Mad Seer not See him and thus can't counter his plans, but he's shown to be immune to prophecy, leading to him breaking three or four prophecies, including Jasmine's plan to be reborn via Cordelia.
* Ranma becomes one for not only Minaka and his Sekirei game in ''[[https://www.fanfiction.net/s/11701126/1/Anything-Goes-Game-Changer Anything Goes Game Changer]]'' but Higa as well, the latter without even being aware of the man's existence. Besides Ranma interfering with unfair battles, mostly preventing Sekirei from being forcibly winged, he and Uzume pose for pictures for Nabiki to raise money (to cover his living expenses). Uzume's cut is enough for her to pay off her Ashikabi's hospital bills, which were being used by Higa to blackmail her.
* In ''FanFic/CardcaptorRad'', the Decepticons plan to [[spoiler: invade the Autobot base]] actually ''works''. They likely would have succeeded in [[spoiler: attaining the Star Saber]] if not for [[spoiler: the humans and mini-cons being there]].

** [[spoiler: Michael's poisoned glass]] breaks before they have a chance to [[spoiler: drink from it]].
** [[spoiler: Gavin and his clone]] manage to catch themselves, preventing them from [[spoiler: falling in the mousetraps]].
** ''None'' of [[spoiler: the arrows]] wind up hitting [[spoiler: Chris]].
** When reaching for the extra gun, [[spoiler: Burnie]] spots [[spoiler: the scorpian]] and shoots it.
** [[spoiler: Gus]] slams the door on the Killer.
** [[spoiler: Adam]] trips over a cord just as [[spoiler: the Killer is about to strangle them]].
** [[spoiler: The puma]] decides they're more interested in being [[spoiler: petted by Lindsay]] than [[spoiler: mauling her to death]].
** The part of [[spoiler: the treadmill]] that [[spoiler: Miles is glued to]] ''breaks off completely''.
* ''Fanfic/GuardiansWizardsAndKungFuFighters'':
** During the Battle of Torus Filney, the Rebellion's strategy hits a major stumbling block when [[LizardFolk Simon]] shows up, due to not having planned for his presence. But then they're able to turn the tables on Servantis' forces when they reveal that [[spoiler: [[SuperweaponSurprise they have guns]]]].
** Cedric and Wong's plot to [[TheStarscream betray Phobos]] and steal the Heart of Meridian from him catches [[TheChessmaster Nerissa]] completely off guard, throwing her own plans completely OffTheRails.
* Examples in ''Manga/MyHeroAcademia'' fanfic ''Fanfic/ConversationsWithACryptid'':
** Midoriya discussed this with All For One, as he discovers that something must have happened for the murderous supervillain to put his plans on hold. All For One cryptically says that plans can change. [[spoiler: In fact, it was because of his marriage to Inko and Midoriya being born that caused All For One to change his plans so he could stay with them and/or keep them safe.]]
** Another spanner is [[spoiler: the Sludge Villain]] who proceeds to kidnap Midoriya, eventually resulting in [[spoiler: All For One breaking out of prison to rescue his son.]]
* Fanfic/ZumasFear: [[spoiler:Believe it or not, Zuma ends up screwing Stone’s EvilPlan after the death of his family.]]
* ''Fanfic/HellsisterTrilogy'': During the Apokoliptian War, ComicBook/{{Darkseid}} is always at least three steps ahead of his enemies, and he comes very close to win. His plan only fails because of one factor he couldn't have foreseen: ComicBook/{{Supergirl}} being near from D'reema right when he spoke the Anti-Life Equation. Before succumbing to the Anti-Life Equation, which destroys Free Will, Kara had just enough time to hypnotize D'Reema into speaking the opposite Equation, thus cancelling out its effects.
* ''Fanfic/FateHaremAntics'': The entire fic is about Irisviel, who is trapped in the Holy Grail but in full control of it, deciding to use the upcoming Holy Grail War to get her son Shirou a harem. All the existing plots and plans promptly get derailed as Iri makes sure all the Masters and Servants besides Shirou are female. Specific examples are:
** Iri's father planned to summon Hercules as a Berserker and force his granddaughter Illya to serve as Master. Iri summoned [[https://typemoon.fandom.com/wiki/Minamoto-no-Raikou Minamoto no Raikou]] instead. Likewise, Iri has some limited ability to speak to her daughter through the Grail, so unlike in canon where Illya hated Shirou and their father (because her grandfather lied to her), Illya knows that their father never abandoned her, and is looking forward to meeting Shirou.
** Bazett tried to summon Cú Chulainn as Lancer, but Iri gave her [[https://typemoon.fandom.com/wiki/Scáthach Scáthach]] instead. More importantly, when Kirei tried to murder Bazett for her Command Seals, Iri briefly stopped his artificial heart, distracting him at a critical moment and ruining the opportunity.
** Sakura summoned [[https://typemoon.fandom.com/wiki/Medusa_(Rider) Medusa]] as Rider, as in canon. Zouken tried to force Sakura to give control over to her brother Shinji, but Iri deliberately made the summoning more explosive than usual, causing the ceiling to fall on Zouken. Sakura and Rider escaped in the confusion.
** After Zouken recovered from having a ceiling drop on him, he summoned a Servant himself, deciding an Assassin would fit him best. Iri gave him [[https://typemoon.fandom.com/wiki/Hassan_of_Serenity Hassan of Serenity,]] a PoisonousPerson. Zouken didn't realize that, slapped her for her perceived disobedience, and [[CruelAndUnusualDeath melted]]. And since Iri had severed his connection to Sakura (which she could only do after Sakura made her contract with the Grail), he couldn't draw power from her and [[OutOfContinues stayed dead for good]].
** Iri did this to herself with Assassin: Since the intent is for Shirou to have sex with all the girls, the fact that she can't touch anyone without killing them is a problem. Iri quickly summons [[https://typemoon.fandom.com/wiki/Mash_Kyrielight Sir Galahad]] as Shielder, who has the power to resist poisons and can pass this onto her allies. And she makes Caren, Kirei's long-lost illegitimate daughter, her Master just to mess with Kirei.
** And Iri ''again'' manages to do this to herself. By summoning Shielder and Ruler, she broke the normal limits on number of Servants and left the door open for others to be summoned. Three separate groups start summoning Servants of their own. Iri can't shut them down, but she can make sure the Servants and Masters are all female. She gives the Ainsworth family [[https://typemoon.fandom.com/wiki/Jeanne_dArc_Alter Jeanne Alter]] as Avenger, but instead of letting Julian become the Master as they intended she grabs his sister Angelica. She gives Fiore of the Yggdmillennia clan [[https://typemoon.fandom.com/wiki/Oda_Nobunaga_(Archer) Oda Nobunaga]] ([[HistoricalGenderFlip who is female in the Nasuverse]]) as Gunner. And Miyu wasn't trying to summon a Servant at all, but didn't understand how the Grail War worked and got [[https://typemoon.fandom.com/wiki/Elizabeth_Báthory Elizabeth Bathory]] as Temptress.
* ''Fanfic/DevilsDiary'': Before his first outing, Magneto looked into the then-current cadre of heroes and villains and decided neither of them would want or be able to stop his coup. Yet still he was driven away by five heroes who nobody had previously seen before... although he KNEW who they were working for.
-->Damnable adolescent yearlings, every one of them, like the beardless youths Hitler put against the Allies when all his other defenses were cracking. Except these yearlings had power. None of them equal to mine, individually. But they knew how to effectively combine what they had. And they had luck, three times damned three times luck, and NO ONE HAD EVER SEEN THEM BEFORE.\\
All mutants.\\
Three males, one female, and one snow-being whose sex is impossible to determine at this point.\\
An unknown quantity.\\
An x-factor.\\
A XAVIER FACTOR.

* ''Fanfic/Team8'': In Chapter 17, Kurenai tells Manga/{{Naruto}} to use his chakra pulse to dispel the genjutsu Kabuto put on the stadium. Naruto overpowers the pulse so much it ends up covering the entire village - causing Orochimaru's plan to fall to pieces twice over, as not only did it dispel the jutsu that were going to summon the giant snakes, it also destroys the barrier he had put to prevent people from interfering with his duel with the Third Hokage.

** And Iri ''again'' manages to do this to herself. By summoning Shielder and Ruler, she broke the normal limits on number of Servants and left the door open for others to be summoned. Three separate groups start summoning Servants of their own. Iri can't shut them down, but she can make sure the Servants and Masters are all female. She gives the Ainsworth family [[https://typemoon.fandom.com/wiki/Jeanne_d'Arc_Alter Jeanne Alter]] as Avenger, but instead of letting Julian become the Master as they intended she grabs his sister Angelica. She gives Fiore of the Yggdmillennia clan [[https://typemoon.fandom.com/wiki/Oda_Nobunaga_(Archer) Oda Nobunaga]] ([[HistoricalGenderFlip who is female in the Nasuverse]]) as Gunner. And Miyu wasn't trying to summon a Servant at all, but didn't understand how the Grail War worked and got [[https://typemoon.fandom.com/wiki/Elizabeth_Báthory Elizabeth Bathory]] as Temptress.

** Iri's father planned to summon Hercules as a Berserker and force his granddaughter Illya to serve as Master. Iri summoned [[https://typemoon.fandom.com/wiki/Berserker_(Fate/Grand_Order_-_Raikou) Minamoto no Raikou]] instead. Likewise, Iri has some limited ability to speak to her daughter through the Grail, so unlike in canon where Illya hated Shirou and their father (because her grandfather lied to her), Illya knows that their father never abandoned her, and is looking forward to meeting Shirou.
** Bazett tried to summon Cú Chulainn as Lancer, but Iri gave her [[https://typemoon.fandom.com/wiki/Lancer_(Fate/Grand_Order_-_Scáthach) Scáthach]] instead. More importantly, when Kirei tried to murder Bazett for her Command Seals, Iri briefly stopped his artificial heart, distracting him at a critical moment and ruining the opportunity.
** Sakura summoned [[https://typemoon.fandom.com/wiki/Rider_(Fate/stay_night) Medusa]] as Rider, as in canon. Zouken tried to force Sakura to give control over to her brother Shinji, but Iri deliberately made the summoning more explosive than usual, causing the ceiling to fall on Zouken. Sakura and Rider escaped in the confusion.
** After Zouken recovered from having a ceiling drop on him, he summoned a Servant himself, deciding an Assassin would fit him best. Iri gave him [[https://typemoon.fandom.com/wiki/Assassin_(Fate/Prototype:_Fragments) Hassan of Serenity,]] a PoisonousPerson. Zouken didn't realize that, slapped her for her perceived disobedience, and [[CruelAndUnusualDeath melted]]. And since Iri had severed his connection to Sakura (which she could only do after Sakura made her contract with the Grail), he couldn't draw power from her and [[OutOfContinues stayed dead for good]].
** Iri did this to herself with Assassin: Since the intent is for Shirou to have sex with all the girls, the fact that she can't touch anyone without killing them is a problem. Iri quickly summons [[https://typemoon.fandom.com/wiki/Shielder_(Fate/Grand_Order) Sir Galahad]] as Shielder, who has the power to resist poisons and can pass this onto her allies. And she makes Caren, Kirei's long-lost illegitimate daughter, her Master just to mess with Kirei.
** And Iri ''again'' manages to do this to herself. By summoning Shielder and Ruler, she broke the normal limits on number of Servants and left the door open for others to be summoned. Three separate groups start summoning Servants of their own. Iri can't shut them down, but she can make sure the Servants and Masters are all female. She gives the Ainsworth family [[https://typemoon.fandom.com/wiki/Avenger_(Fate/Grand_Order_-_Jeanne_Alter) Jeanne Alter]] as Avenger, but instead of letting Julian become the Master as they intended she grabs his sister Angelica. She gives Fiore of the Yggdmillennia clan [[https://typemoon.fandom.com/wiki/Archer_(Fate/KOHA-ACE) Nobunaga Oda]] ([[HistoricalGenderFlip who is female in the Nasuverse]]) as Gunner. And Miyu wasn't trying to summon a Servant at all, but didn't understand how the Grail War worked and got [[https://typemoon.fandom.com/wiki/Lancer_(Fate/Extra_CCC) Elizabeth Bathory]] as Temptress.

* ''Webcomic/Misfile'': It turns out [[spoiler: Rumisiel]] managed to throw a huge monkey wrench into a plot to destroy the CelestialBureaucracy and remake the world and humanity by [[spoiler:taking the key to his wing of the filing system with him when he got exiled, keeping it out of the wrong hands.]]

* In the fourth chapter of ''VisualNovel/Danganronpa2GoodbyeDespair'', Hajime is able to figure out who committed that chapter's murder [[spoiler:because Fuyuhiko happened to wake up during the night and saw the victim heading downstairs, then sat down in the lounge and spaced out for a while. Fuyuhiko's presence in the lounge prevented the killer from returning to their room after carrying out their plan, and thus they couldn't secure their alibi of being fast asleep when their time-delayed murder method went off. Instead, the killer had to pretend they had left their room along with everyone else to investigate the ringing alarm clock in the lounge, which is proof they weren't in their room in the first place since they had one of the Deluxe rooms, which were completely soundproof]].
** In [[VisualNovel/DanganronpaTriggerHappyHavoc the preceding game]], the entire triumph of hope over despair on Earth hinges on a poorly-fitting bathroom door that gets stuck in the doorframe. A door which, because of Naegi's Ultimate-level luck (which manifests as [[UnluckilyLucky seemingly-bad luck that turns out to be good luck in disguise]]), gives him an alibi for a crime he would otherwise have been framed and executed for. [[MessianicArchetype Given how important Naegi would go on to be to the future of humanity]], it's no exaggeration to say that ''that'' was the moment that [[spoiler: Junko's]] fate was well and truly sealed. Even worse, it's implied that [[spoiler: she]] deliberately ''gave'' him the crappy door just because [[ItAmusedMe the idea of the Ultimate Lucky Student being the only one with a crappy door was funny]].

* ''Webcomic/SchlockMercenary'': In Book 15 Schlock ends up derailing a StagedPopulistUprising simply by drawing the attention of a police officer [[spoiler:who was unwittingly carrying a bomb that was supposed to blow up the heads of the popularly elected legislature, providing the pretext for the fake revolt.]]

** In [[VisualNovel/DanganronpaTriggerHappyHavoc the preceding game]], the entire triumph of hope over despair on Earth hinges on a poorly-fitting bathroom door that gets stuck in the doorframe. A door which, because of Naegi's Ultimate-level luck (which manifests as [[UnluckilyLucky seemingly-bad luck that turns out to be good luck in disguise]]), gives him an alibi for a crime he would otherwise have been framed and executed for. [[MessianicArchetype Given how important Naegi would go on to be to the future of humanity]], it's no exaggeration to say that ''that'' was the moment that [[spoiler: Junko's]] fate was well and truly sealed. Even worse, it's implied that [[spoiler: she]] deliberately ''gave'' him the crappy door just because [[ItAmusedMe [[spoiler: she]] thought the idea of the Ultimate Lucky Student being the only one with a crappy door was funny]].

** Naegi's luck is deliberately referred to as a "spanner in the works" by [[spoiler: Junko]]; no matter how CrazyPrepared [[spoiler: she]] is for every possible scenario, Naegi's luck is totally unpredictable and can throw everything off on a dime, which is why [[spoiler: she's]] captivated by him.