->''"In a situation that's already a powderkeg, one doesn't ignore the man handing out matchbooks."''
-->-- '''[[http://freefall.purrsia.com/ff1400/fc01340.htm Florence Ambrose,]]''' ''Webcomic/{{Freefall}}''

A character unintentionally plays a [[SmallRoleBigImpact small and/or unlikely but crucial role]] in some horrible development (usually this action serves as the catalyst).

An Unwitting Instigator Of Doom can be basically complicit with the villain, but in that case, they're generally seeing only a small portion of the picture. If they're being specifically manipulated but do not realize, they're an UnwittingPawn. Other times, they're simply blundering in like a [[SpannerInTheWorks wrench in some particularly highly valued machine]]. They may also end up as the IdiotHoudini.

Compare NiceJobBreakingItHero for when the heroes cause doom, and MikeNelsonDestroyerOfWorlds for a different type of unwilling doom bringer. Also compare ChekhovsGunman, in which a seemingly insignificant character becomes more important later on. See also InterruptedCooldownHug and EndangeringNewsBroadcast.
----
!!Examples

[[foldercontrol]]

[[folder:Anime & Manga]]
* ''Manga/DragonBall'':
** In the original series, [[HarmlessVillain Emperor Pilaf]] releases [[SealedEvilInACan Demon King Piccolo]], who promptly proceeds to [[HeroKiller have many of the world's leading martial artists killed]], including Goku's best friend, Krillin, and nearly takes over the world. Pilaf hopes to be able to be rewarded by Piccolo with his own territory, only to be backstabbed. Nice job nearly dooming the world, shorty.
** However, in releasing Demon King Piccolo, not only did Pilaf ensure that Goku would grow up to be a warrior trained by God himself, and thus be powerful enough to put up a fight (with the reborn Piccolo) to kill Raditz, then get training from Kaio-Sama to defeat Vegeta, later accidentally recreate the Super Saiyan transformation to defeat Frieza, defeat Cell who was created by Gero in retaliation for the destruction of the Red Ribbon Army (which happened a while before Pilaf freed Piccolo) and would have wiped out humanity had it not been for Goku training Gohan, and then finally defeat Majin Buu. In short, had it not been for Pilaf, humanity would have been enslaved by Raditz, the Earth would have been sold to Frieza, Cell very likely would have wrought havoc on the universe then, until Babidi revived Majin Buu who would have killed everything in the Universe... so, uh... [[NiceJobFixingItVillain "thanks for indirectly saving the Earth" Pilaf?]]
** ''Anime/DragonBallZ'':
*** Remember how Majin Buu became truly evil, killed off half of the Z-warriors, the entire human race, and then finally blew up Earth? It all happened because of a few goons in the episode "The Evil of Men", where they attack and shoot Bee (Buu's pet puppy) and Hercule (Buu's new best friend who was in the process of rehabilitating him). As a consequence Buu snapped and steamed out [[EnemyWithout Evil Buu]], who then [[SplitPersonalityTakeover proceeded to absorb him]]; the entire rest of the Buu saga is the ''entire universe'' paying the price for what those thugs did.
*** On another side, Goku believed that he could have easily killed the fat Majin Buu at Super Saiyan 3, but deliberately chose ''not'' to because he wanted to give Trunks and Goten a chance at doing so, and because, since he was already dead, he didn't want the next generation to think they could just depend on him all the time. Thus, through inaction, Goku is, in a way, responsible for Super Buu coming forth.
*** It happens again in ''Anime/DragonBallZResurrectionF'', where Pilaf and his gang help bring Frieza back to life.
* ''Anime/CodeGeass'':
** In season 2 [[TheDragon Schneizel]] makes a case to the Black Knights to surrender their leader Zero, who he reveals is his long-lost half-brother, Lelouch vi Britannia. While not without their doubts towards their leader based on some of his actions, they, at least counting the likes of Tamaki and Diethard, remain wary and skeptical towards Schneizel, who is rightfully suspected to be just as easily tricking them with the evidence and testimonies that he is presenting. Not more than a few moments later does Ohgi come along with his still secret love interest Villetta, a Britannian spy, with some additional cursory yet suspicious evidence the latter provided that leads everyone else amongst the Black Knights present into deciding [[KangarooCourt to turn on Lelouch without giving any chance of there being a case made in his favor]].
** This is significant in that afterwards, Lelouch [[DespairEventHorizon believes there is no turning back for himself given what he has already suffered in the past in addition to this]], and basically goes from a WellIntentionedExtremist who at least had a sensible blueprint for neutralizing Britannia and had gotten as far as setting up a legitimate international front to that end to [[TheUnfettered throwing away any last inhibition he had]], [[spoiler:and using a GenghisGambit of questionable necessity, evidently to fulfill a [[DeathSeeker death wish]]. The person responsible for this chain of events? HappilyMarried to the other person responsible, Villetta, and evidently elected as Prime Minister of Japan, making him among the few characters to get a HappyEnding in a mostly BittersweetEnding. A more peaceful final solution to the global conflict could have been arrived at that would have also resulted in Lelouch living on and not abandoning his loved ones, or making the questionable decision of leaving [[IdiotHero Suzaku]] with the role of Zero]].
** Rolo also has a role in instigating doom. Had he not murdered someone close to Lelouch, he wouldn't have prompted him to raid a camp where Britannia was preforming experiments to create more {{child soldier}}s like Rolo and pretty much kill everyone there. If that hadn't happened, Schneizel wouldn't have as much evidence against Lelouch as he would, which would probably have changed about half of the story. If you count him as such, Jeremiah also shared the blame. Why? [[spoiler:Had he not used his Geass Canceller, he wouldn't have restored Shirley's memories and she wouldn't have confronted Rolo, thus causing the above to happen]].
* ''Manga/DeathNote'':
** Misa Amane does this twice, to the severe detriment of [[ALighterShadeOfGray both sides.]] Once, it's as a PoisonousFriend to Kira, [[spoiler:giving L physical evidence in the case in her sending the tapes]], and the other time, it's out of MadLove to same, [[spoiler:endangering her own life to the point that her shinigami has to intervene]]. For a fervent Kira supporter, she's really a bit of a loose cannon: she never seems to fully appreciate her role in either disaster.
** Sachiko asks her children to bring their father a change of clothes, and Sayu is reluctant to take the task. When Light volunteers, he ends up running into Naomi, learning about how close she is to figuring out an important part of how he kills people, and silencing her before she can reach L.
** Aizawa opens up his umbrella when it begins to snow and so ''just'' misses seeing Light and Naomi Misora together.
** Teru Mikami [[spoiler:breaks his "once-a-month-to-the-bank" routine after learning that Mello has kidnapped Takeda in order to dispose of any loose ends. However, he is unaware that Light has also done the same thing, making his actions unnecessary. But he managed to tip Near to the location of the ''real'' Death Note he was using, resulting in the failure of Light's final gambit and his downfall.]]
* ''Manga/{{Naruto}}'':
** Aoba Yamashiro. Don't know him? He's a recurring background ninja who was probably never formally introduced, databooks aside. Why is his name so well-known in some parts of the ''Naruto'' community? A single careless sentence out of Aoba's mouth revealed Itachi's whereabouts and goals to Sasuke. Following that, Sasuke tried to beat up Itachi, was soundly defeated, and pondered why Itachi would be interested in Naruto. Sure, Sasuke wasn't particularly stable before, but this huge blow to Sasuke's self-esteem was the catalyst for the event that would finally send Sasuke over to TheDarkSide.
** Kakashi, ''of all people''. [[spoiler:He speaks about Naruto's birth at Rin's grave, and it just ''so happens'' that Tobi/Obito happened to overhear it, resulting in ''the Nine-Tailed Fox's fateful attack'' and the death of the Fourth Hokage]]. Furthermore, had Kakashi not [[spoiler:abandoned his principles and went back to help Obito save Rin, then Obito would have died. If Obito had died then, then Naruto's parents would still be alive, Naruto wouldn't have been ostracized by the village in his youth, Nagato would have been less crazy, the Rain Village wouldn't have committed as much genocide, Madara's plan would have died with him, the Jinchuriki would still be alive, the Uchiha Massacre might have been stopped, the Fourth Great Shinobi World War wouldn't have happened, and the Ten Tails wouldn't have been revived to wreak destruction upon the world.]]
** Jiraiya, by taking pity on the three Rain orphans and training them. They grow up to be revolutionaries in their own village, and after [[spoiler:Yahiko dies, Nagato turns evil, helps form Akatsuki with Tobi/Obito and Konan, and becomes an enemy of the Leaf Village, killing Jiraiya and devastating the village.]]
** Danzo does this quite a bit. He means well [[WellIntentionedExtremist kind of]] but he's [[JerkAss kind of a dick]] and his actions tend to cause people to make {{Face Heel Turn}}s. He's responsible for the StartOfDarkness of [[spoiler:Nagato/Pain and Kabuto]], worked closely with [[spoiler:Orochimaru]], and is one of the three major contributors to the tragedy of [[spoiler:Sasuke and the Uchiha clan massacre.]]
** The biggest example might be Tobirama Senju, [[spoiler:the ''Second Hokage''. His bigotry towards the Uchiha clan set a lot of the plot in motion, and he created Edo Tensei.]]
** His brother Hashirama isn't much better, as [[spoiler:he prevented Tobirama from killing Madara Uchiha before the Leaf Village was even founded.]]
** This trope is PlayedForLaughs in ''Manga/RockLeesSpringtimeOfYouth''. Whenever Hinata appears, expect someone to get hurt. Most of the time it's Naruto getting the receiving end of Neji's 8 Trigrams 64 Palms.
* In an early ''Anime/{{Pokemon}}'' episode, Ash is right on the verge of capturing a Weedle, when he is rudely interrupted by a samurai, who challenges him to a Pokémon match. During said match, which is a MirrorMatch between their two [[StoneWall Metapod taking Harden commands]], the Weedle manages to escape back into its tree and alert the Beedrill, who capture Ash's Metapod. In one of the series' earliest {{Broken Aesop}}s, Ash is forced to learn a lesson about not making excuses about not finishing what he started, even though it was the fault of the samurai, [[NeverMyFault who berates him for all of this]], that Ash wasn't able to finish in the first place, all because he didn't have the courtesy to wait until Ash was done. Even after all is said and done, and Ash rescues Metapod, he's still short one Weedle, which would eventually evolve into a Beedrill.
* Hitomi Shizuki of ''Anime/PuellaMagiMadokaMagica''. There's this friend of hers, Sayaka, who likes Kyousuke, who lost the use of his arm in an accident. Hitomi also loves Kyousuke and decides to confess to him, but not before offering Sayaka the first shot since she believes it's the fair thing to do [[LockedOutofTheLoop and has NO idea that Sayaka REALLY can't confess]]. [[spoiler:Sayaka doesn't act on Hitomi's offer, her depression only worsens when she sees Hitomi confess to Kyousuke, and because of the nature of her DealWithTheDevil she [[AndThenJohnWasAZombie becomes what she fights]]. Kyouko self-destructs to MercyKill Sayaka]]. In short: Because of one mis-timed confession, two girls died.
** Some consider Madoka to be one. [[spoiler:Had she not tossed away Sayaka's Soul Gem, she wouldn't pass out/go all corpse-like and Kyubey wouldn't have spilled the beans, thus giving Sayaka that state of mind that she's no longer human.]] Although to be fair, her mother Junko also falls into this line for giving her that idea, although Madoka was not only ignorant of [[spoiler:what happens when a magical girl is separated from her Soul Gem]], but in addition to not mentioning that, gave her mother a vague description of what Sayaka was going through. As such, it becomes nearly impossible for Junko to give any good advice on that subject.
*** Kyouko is also to blame. [[spoiler:Had ''she'' not challenged Sayaka to fight, the already emotionally-unstable Madoka wouldn't had flipped her shit and tossed the Soul Gem to stop the eventual fight]].
** Madoka gets another one too: [[spoiler:Because she brought a mousy little introvert into their fold who took a great liking to Madoka, said introvert, Homura Akemi, became a ShellShockedVeteran. Moreover, in almost all of the timelines poor Madoka either dies or becomes the most powerful witch ever, due to Homura using her powers making Madoka more and more powerful as both a magical girl and a witch.]] It should be noted, however, that this is also what ends up [[spoiler:ending the very concept of Witches in the universe altogether.]]
*** Extrapolating on the above, the Drama CD reveals ''yet another one'': [[spoiler:the original Madoka's wish was to save a cat who was about to get hit by a car. Said cat, Amy, would eventually cause Homura and Madoka to make a bond, which would then result in Homura contracting, which would result in all the timeloops, etc. etc.]]
** Homura becomes one as well in the Rebellion Story. [[spoiler:In the ending, she tells Kyubey of the Witch system, which because of what happened above is now just an unheard of thing for him. Bad idea, as he rigs the system to place Homura in a false world so that he could steal Madoka when she comes to save Homura just so he can use the Witch system again. ''Very'' bad idea for him though, as Homura takes matters into her own hands and ''she'' kidnaps Madoka, becoming the new Goddess. In a way, this trope zig-zagged, as Homura's mistake actually ''benefited'' her in the end... though it had to take someone else's mistake.]]
* ''Manga/{{Bleach}}'': Uryuu Ishida's use of hollow bait to start a hollow hunting contest with Ichigo has the unintended side effect of causing a massive onslaught of hollow attacks on the town, that even draws in a Menos Grande. Uryuu is utterly baffled by this because he used only a tiny amount of a weak bait that should never have attracted so many hollows, let alone anything as powerful as a Menos Grande. The further unintended consequence is that the Menos Grande incident alerts Soul Society to both the AWOL Rukia's location and the fact she's AWOL due to having illegally given her power to a human, thus setting off the Soul Society arc. [[spoiler:It's eventually revealed that Aizen manipulated the event to cause the onslaught because he both wanted to test Ichigo's power and alert Soul Society to Rukia's location whereupon he could fake orders from TheGovernment to have Rukia retrieved and sentenced to execution to further his plans.]]
* In ''Manga/{{Bakuman}}'', one factor that contributed to Detective Trap losing popularity [[spoiler:and being canceled]] is two other similar manga- Phantom Thief Cheater and Detective Gosuke Akechi- both of which were submitted while Mashiro was in the hospital and on hiatus, and debuted after Mashiro's release.
** Near the end of the series, Mashiro mentions his relationship with Azuki around one of his assistant Kato's friends, who posts about it on her blog. As a result, [[spoiler:an in-universe InternetBackdraft [[YokoOhNo against poor Azuki]] ensues, and Azuki's bosses urge her to deny her relationship with Mashiro. She refuses, and ultimately has to outperform '''all''' other contenders to get the lead role in Mashiro's anime]].
* ''Anime/DragonBallGT'': As revealed in the final arc, the entire reason the Dragon Balls scatter across the world after each wish is to give the negative energy within the balls the chance to disperse, as it's supposed to take years just to find one ball. Sadly, when Bulma created the Dragon Radar, that protective measure was completely nullified, allowing the Z-Fighters to find the balls and summon Shenron repeatedly, leading to the birth of the [[MadeOfEvil Shadow Dragons]].
* ''Anime/NeonGenesisEvangelion''. The pilots of Evangelion Transport Neopan 400, the American Weather Bureau and the technician at Airbase Ekta 64 are never named, are never spoken of again, but ALL are responsible for the entire [[KnightOfCerebus Bardiel Incident]] and CerebusSyndrome the show developed towards the later half. Long story short: not going around the suspicious-looking cloud equals TheEndOfTheWorldAsWeKnowIt.
* [[spoiler:Takehiko Henmi]] from ''Manga/OniisamaE''. [[spoiler:Six years before the story started, he visited his best friend Takeshi Ichinomiya's house and befriended his little sister Fukiko, who unbeknownst to Takehiko got a huge PrecociousCrush on him. She made him promise that he'd attend her birthday party and hear her play the violin, but he couldn't get to the Ichinomiya mansion in time and [[HeroicBSOD Fukiko was completely crushed]], becoming a {{Yandere}} over him.]]
* In Creator/RiyokoIkeda's other manga, ''Manga/{{Claudine}}'', we have [[spoiler:Rosemarie]]. What did she do? [[spoiler:Depressed because Claudine doesn't return her feelings ''and'' she has found out that Claudine's crush Cecilia is actually [[YourCheatingHeart the lover of Claudine's *father* Auguste]], she mentions this very complicated deal to her teacher Louis, who is also Cecilia's younger brother.]] Little did she know that [[spoiler:Louis ''also'' had been Auguste's lover in the past... and that he would go {{Yandere}} on Auguste and Cecilia.]] The result isn't pretty: [[spoiler: Auguste and Cecilia die, the maddened Louis disappears, the Montesse family is devastated, and Rosemarie herself [[TwoFaced gets half her face horribly burned]].]]
* [[spoiler:Satoshi Oginome]] from ''Anime/MawaruPenguindrum''. [[spoiler:Had his estranged daughter Ringo not seen him with his girlfriend and her daughter, she would've likely not sped up her "Project M" to bring her family back together via the AttemptedRape of her crush, with all that happened later.]]
* Inverted with Isumi in ''Manga/HikaruNoGo''. If he hadn't insisted on playing Hikaru, [[spoiler:Hikaru would never have discovered that Sai is still present in his Go, would not have started playing again, would not have become the "second genius" and, therefore, [[UnintentionalBackupPlan would have caused the thousand-year plan of the god of Go to fail]]. At least, unless the whole chain of events [[GambitRoulette was just another part of the plan]].]]
* In ''Anime/DigimonSavers'' pretty much every bad thing can be blamed on one villain, the FinalBoss is just reacting to events. Drasil is such a self righteous blowhard that many people hated it just as much as the guy responsible for everything though, especially since much drama could have been avoided if Drasil had bothered to [[OrcusOnHisThrone get off its throne]] years ago.
* ''Anime/DigimonAdventure02'' has [[spoiler: Cody/Iori's grandfather, Chikara Hida. His son, Hiroki (Cody's father), was the only friend that eventual BigBad Yukio Oikawa had during his childhood, and he forcibly separated them, causing Oikawa to become an isolate and despaired man in his later years, obsessed with fulfilling the dream they had as children. This made him an easy prey for Myotismon's corruption, and drove him to orchestrate the events of the whole season. In the final episodes, Chikara seemed to have realized his mistake, but it was too late by then.]]
* In ''Anime/SailorMoon'': Sailors Uranus and Neptune believe that victory cannot be attained without some [[MartyrWithoutACause horrible angsty sacrifice that only they have the moral strength to make]]. So basically, they make such choices that would make things worse at the end of the run. What they did in the GrandFinale is a major example in their habit to make bad decisions: [[spoiler:in a desperate gambit to reach for Galaxia themselves and keep their beloved Moon from dying, they pull a FakeDefector act that includes [[KillTheCutie killing Pluto and Saturn]] (depriving Moon of two valuable allies ''right after the death of Princess Kakyuu and the {{Heroic Sacrifice}}s of the Inners''), attacking Moon herself and her remaining allies the Starlights (so she wouldn't suspect them, but also [[CurbStompBattle weakening her physically]] [[BreakTheCutie and devastating her emotionally]]) and ultimately attack Galaxia on their own using powers she gave them after they faked choosing to serve her. But they didn't count on [[NoSell Galaxia being immune to the attack]] and they end up dying in front of Moon, Chibi-Chibi Moon and the Starlights [[SenselessSacrifice without accomplishing anything in the end]].]]
* ''MedakaBox'': Onigase, and by extension, the Public Morals Committee. Their antagonism towards the Student Council ends up getting Medaka and the other members dragged into the Flask Plan. In addition, Medaka's defeat of Unzen makes her an ideal candidate for the project and thus a target.
* In ''Anime/MagicalGirlLyricalNanohaAs'', Suzuka serves as one. She, not knowing about the Wolkenritter’s true nature or activities despite having met them as well as Hayate, plans to pay Hayate a surprise visit along with Arisa, Nanoha and Fate on Christmas Eve in Hayate’s. Nanoha and Fate, seeing the Wolkenritter with Hayate, then realize that Hayate is the true master of the Book of Darkness that they are searching for, and are forced into a confrontation with the Wolkenritter, who wish to prevent Hayate from being exposed. [[FromBadToWorse Things quickly get worse from there.]]
* In ''MaiOtome Sifr'', a cat wandering out on the hotel balcony leads to Sifr trying to retrieve it, and falling and having to be rescued by Lena, who berates her for going outside and risking being discovered. It's revealed that one of the poolgoers was an undercover Schwarz agent, and that night, a large Schwarz force attacks, succeeding in kidnapping Sifr with help from M9.
* [[spoiler:Michiru Saotome]] from ''Manga/GetterRobo Armaggedon''. [[spoiler:She's [[FateWorseThanDeath infected with]] TheVirus, and chooses to commit suicide via [[BetterToDieThanBeKilled screwing up with a test flight]] rather than suffer a really painful death]]. While such a situation is really bad and one can sorta understand the logic behind such a drastic decision, there are even worse things about it: [[spoiler:her father, Dr. Saotome, mistakenly believed that the Getter pilots were to blame, leading to him becoming a MadScientist... which is followed by his murder, Ryoma's imprisonment, Saotome being BackFromTheDead and completely AxCrazy, '''and''' the invasion.]] (Not to mention [[spoiler:her [[RaisedAsTheOppositeGender little sister Genki]], [[HarmfulToMinors who witnessed Michiru's death in first row]], is [[BreakThecutie horribly traumatised]] to the point of becoming a CreepyChild]]). On top of that, said incident drove a rather large wedge between Getter pilots Ryoma and Hayato, to the point where each of them outright wants to murder the other at the start of the story; it isn't until '''several''' years later, when they learn the truth about [[spoiler:Michiru's death]] that they start really working together the way they did back as teammates.
* In ''Manga/FullmetalAlchemist'', Heinkel manages to corner Pride, only for some residents of the nearby slums to come by with sources of light. This enables Pride to set fire to the brush nearby, regain use of his shadow powers and severely wound Heinkel.
** Earlier on, Edward and a nameless character share responsibility for [[spoiler:Winry getting a HeroicBSOD and trying to kill Scar, potentially putting her own life in danger]]. The former mentions [[spoiler:Scar killing Winry's parents]] while unbeknownst to him, [[spoiler:Winry]] is in earshot, and the latter, an MP knocked out by Scar, accidentally leaves behind a pistol for [[spoiler:Winry]] to pick up.
* [[spoiler:Kalos Eidos]] from ''Anime/KaleidoStar'' believes himself to be one of these. [[spoiler:Ten years ago, he asked a famous acrobat and close friend of his named Aaron if he truly was up to performing the very dangerous Fantastic Maneouver, that had caused more than one death... and afterwards, Aaron failed to do it and died]]. This is the reason why, a decade later, [[spoiler:Aaron's son and former Kaleido Stage Ace Yuri is pissed off at Kalos enough to try buying out the Stage as revenge... and Kalos does nothing to stop him [[TheAtoner since he thinks it's his punishment]] [[MyGreatestFailure for letting Aaron die]].]]
* In ''MaiHime'', while Yuuichi's desire to help Mai is commendable, several of his actions end up making things worse for her.
** Yuuichi uttering Mai's name when he catches her with Reito ''when Shiho is with him as well'' results not only in Reito being upset at him but in Mai attracting Shiho's jealousy, since Shiho accuses Mai of lying to her about Mai's own desire to [[ShipperOnDeck root for her love for Yuuichi]].
** Yuuichi tells an ill Shiho that [[spoiler:Nao is attacking Takumi]]. As a result, [[spoiler:the [[{{Yandere}} increasingly unstable Shiho]] slips out of the hospital and destroys Akira's Child with her Hime powers, killing Takumi out of spite for Mai]].
** When Yuuichi goes to [[spoiler:save Mai from Yukariko]], he also ends up missing an appointment to meet Shiho in the park, [[spoiler:causing the despairing Shiho (who, for worse, is now fully under the influence of [[ManipulativeBastard Nagi]]) to fully lose it and directly attack Mai, leading to a battle that ends in Yuuichi's death]].
** In Mai's past, an unnamed girl called her over to play while she was watching Takumi. While she was gone, Takumi went into the river and almost drowned, forcing his and Mai's mother to save him, leading to her death, Takumi's weakened heart and Mai dedicating herself to taking care of Takumi in order to atone for her mistake.
* In the ''Manga/SoulEater'' manga, most of the arc invading Arachne's castle started up when [[spoiler:Kim]] was suspected of [[spoiler:being a witch]] and a random, nameless DWMA agent decided to immediately arrest her by force instead of talking to her first like everyone else was planning. A bigger example would be [[spoiler:Death attempting to 'free' himself from fear by creating [[MadGod Asura]]. Creating an Anthropomorphic Personification of ''unrelenting terror'' did not go well, as Death apparently made an entity that was a) equal to him in {{p|hysicalGod}}ower and b) unlike his [[EldritchAbomination fellows]] eventually cannot be reasoned with.]]
* In ''Anime/GirlsUndPanzer'', when Hana introduces her friends to her mother, Yukari mentions that she's in a different class from Hana, but they're doing tankery together. Yukari doesn't know that Hana's mother doesn't know [[FantasyForbiddingMother or approve]] of Hana doing so, and Hana's mother ends up fainting on the spot and later (temporarily) disowning her. Yukari apologizes to Hana for her role in this, but Hana doesn't hold it against her, feeling as though it's her own fault for not telling her mother.
** Koume Akeboshi, [[spoiler:whose tank plunged into a river during the previous tournament finals, resulting in Miho abandoning the flag tank to save it, and causing Black Forest to be defeated when their enemies fire on the flag tank]], blames herself for Miho deciding to leave Black Forest, seeing herself as causing Miho trouble.
* In ''Manga/JojosBizarreAdventure'', George Joestar I's well-intentioned adoption of Dio Brando leads to his death, his son's death, his grandson's death, his great-great-great-grandson's death, his great-great-great-great-granddaughter's death, the deaths of countless others, and nearly causes the end of the ''entire universe''.
** Dio's father Dario also counts as one. If only he wasn't such a petty thief and a gigantic {{Jerkass}} of an [[AbusiveParents Abusive Father]], not to mention take care of his wife better, Dio could have tempered the evil within him that he carried since his birth, since it's known that [[EvenBadMenLoveTheirMamas he loves his mother]], instead of causing... well, see above.
* In ''VideoGame/TheKingOfFighters: KYO'' manga, there are three of these: Iori Yagami, Sanae and Takaya Maeta. Iori challenged Kyo to a ''very'' violent fight outside the school grounds, which prompted Kyo's girlfriend Yuki as well as Athena Asamiya to defend him (and in Yuki's case, [[GoThroughMe at great risk to herself]] since she's '''not''' an ActionGirl). The day after this Sanae introduced Maeta to Yuki, trying to rope her into having a date with him despite Yuki's own reluctance. [[spoiler:Unbeknownst to all of them, the botched fight with Iori had triggered Kyo's hidden insecurities -- and it was soon followed by a challenge from Maeta ''and'' Daimon to Kyo, who lost '''badly'''. All of these factors piled up on Kyo's own psyche: soon he was so troubled that he got BroughtDownToNormal, then suffered a '''severe''' HeroicBSOD. If not for Kyo's father Saisyu going WarriorTherapist on him, Kyo would have ended up ''as a BrainwashedAndCrazy BloodKnight completely controlled by {{Orochi}}''.]]
* In Manga/{{Lady}}, a group of English kids are seen playing with a ball in the streets of London during one of the first scenes of the manga... Had one of the kids not gone for their missing ball in the worst moment possible, the car Lynn and her mother Misuzu were in wouldn't have tried to dodge her too fast and wouldn't have crashed, which in turn ''[[DownerBeginning would have not costed Misuzu her life and would've brought much less trauma to Lynn]]''.
* ''Manga/RosarioToVampire [=Capu2=]'': Kokoa is responsible for not one, but two disasters during the anime:
** First, she badmouths curry in front of Apsara, who snaps and force-feeds her special curry to turn her into a "curry zombie" before doing the same to the rest of the school.
** Then, a few episodes later, she steals Lilith's Mirror from the academy with the intent to use it to get Inner Moka back, but ends up mixing up packages with a visiting Kyouko, who inadvertently uses it to cause all of the academy's students to revert to their monster forms and go on a rampage, which almost breaks down the barrier maintaining TheMasquerade and forces Moka to give up her rosary to fix it.
* ''Manga/RoseOfVersailles'': The Duke of Orleans secretly works to discredit Louis XVI and Marie Antoinette and aids individuals unhappy with the monarchy, hoping to use popular support to become King himself. However, the discontent he helps feed leads to a full-scale revolution culminating in the destruction of the ''ancien regime'' and the formation of the French Republic.
* ''Manga/YourLieInApril'': Hiroko was the one who convinced Saki to make Kousei into a pianist after seeing his great talent. After Saki became sick, she became more demanding and abusive towards Kousei, eventually damaging their relationship beyond repair and leaving Kousei with deep emotional scars. Hiroko always blamed herself for Kousei's problems because of it.
[[/folder]]

[[folder:Comic Books]]
* In an issue of one of the ''UltimateMarvel'' comics, Captain America told Spider-Man that he was not ready to be a hero and that he did not deserve to wear the costume. [[spoiler:Spidey's {{determinat|or}}ion to prove Cap wrong is what leads to his untimely death.]]
* In Volume 5 of ''ScottPilgrim'', Stephen Stills tells Knives that before Scott broke up with her, he had already started dating Ramona. Knives then tells Ramona, leading her to [[spoiler:break up with Scott]].
* Inverted in the ''Franchise/{{Tintin}}'' story ''Recap/TintinTheSecretOfTheUnicorn'' with the pickpocket who had been stealing everyone's wallets. [[spoiler:He ended up stealing the Bird brothers' wallets which contained their parchments, this lead them to think that Tintin stole their wallets. They ended up kidnapping Tintin, and after a long chain of events, they got captured. Tintin got the last two parchments from the pickpocket and ended up finding Red Rackam's treasure.]]
* In the ''ComicBook/ArchieComicsSonicTheHedgehog'' book this applies to Sonic, Sally, Knuckles, and Tails's respective families. Issue 50 revealed that Sonic's dad and uncle found Robotnik and brought him to King Max, who made his infamous decision to make him the new Warlord. During this time up to when they were captured, Knuckles' father and ancestors were aware of Robotnik, but devoted none of their considerable resources to resolve those problems, despite Robotnik once trying to weaponize the Floating Island in the Sonic and Knuckles tine-in comic, trying to drive the island into the sea in the Death Egg saga and Knuckles spin off title revealing his family was still living on the island and would've been aware of this; Locke even commented on the Ultimate Annihilator in the spin off title. And almost immediately after they returned, Tails's parents caused a political reformation that may well have resulted in, in addition to [[spoiler:King Naugus]], the disaster Silver's trying to prevent.
* ComicBook/XMen villain [[MasterOfIllusion Mastermind]] when he turned Phoenix into Dark Phoenix. He thought he was merely brainwashing Jean Grey and capturing the X-Men as part of his bid to join the Hellfire Club's Inner Circle. Neither he nor the rest of the club realized they were messing with a cosmic entity and ended up putting the entire universe at risk.
* Having used a XanatosSpeedChess style plan to save the world a few times, Kid Loki find out, to his horror, that pretty much everything he's done during ''ComicBook/JourneyIntoMystery'' has come back to bite him in the ass all at once - the main villain of the Everything Burns crossover is [[spoiler:Surtur]], who was originally released by Loki, he's aided by [[spoiler:The Manchester Gods]], who gained their power with Loki's help, and [[spoiler:Surtur's]] herald is [[spoiler:the alternate version of Leah that Loki had written into the Serpent's backstory]]. Right after he clears all of that up, he discovers that [[spoiler:Mephisto, still angry at Loki for releasing the Disir from their curse, has found out about the Fear Crown that he'd created and if going to use it to create a literal hell on earth]]. Unlike a lot of examples here, because he's the protagonist, it comes across as being more tragic than annoying - no matter what he does, something's going to come along and ruin his happiness and success.
* ''Comicbook/TheTransformers'':
** In the original comic, Octopunch tried to shoot Grimlock during a battle in Cybertron's core. However, the blast harmlessly bounced off the Dinobot leader and instead struck Primus himself, causing him to let out a scream that allowed Unicron to find his way back to Cybertron.
** In the IDW comics, Whirl is a minor example - while the Senate had pressed him into service, Megatron points to him as the one who taught him to rebel against the Senate with violence, thus starting the Great War.
-->'''Whirl:''' Did I ever tell you about how I started '''our''' war? You'll laugh your head off.
* In ''FF #5'', [[ComicBook/FantasticFour Reed and Susan's]] children Franklin and Valeria viewed a set of [[VideoWill holographic wills]] their family left them. Ben confesses his deepest darkest secret in his: [[spoiler:back in college he was pissed off by a certain {{Jerkass}} who kept mocking his best friend Reed. So one day Ben snuck into the guy's room and messed around with one of his experiments...]] This is a doubly appropriate example given the [[SelfDemonstrating/DoctorDoom moniker]] the guy would start using after that day.
* ''StarWars ComicBook/{{Legacy}}'': Obi-Wan once cut off a tusken raider's arm to protect some moisture farmers. That tusken raider was cast out by his tribe, and went on to become a new Sith Emperor who will create the One Sith, and start a new war that was will result in the deaths of billions of life forms.
* ''First X-Men'' has Victor Creed's then girlfriend, Holo die, and he blames Wolverine for convincing her to stay and fight with him. But that shouldn't be a big deal for Victor, who is over one hundred years old, and they only had a short relationship, right? Well, when she was mortally wounded, she used her powers to show Victor an illusion of the two having a family and living a long, fulfilled life, and he thought that was what was happening and experienced it first-hand, and she told him that ''this'' is what he should remember... before cutting the illusion and revealing that she was actually still mortally wounded. She tells him that it "doesn't have to mean anything less". Well, he took this to heart, and determined that it logically meant that Logan had taken it all ''away'', and would spend the rest of his life ensuring that Logan would never find any''thing'' or any''one'' worth living for ever again. So it's less "you got my short-term girlfriend killed" and more "you took away my happy ending". On that day, Holo's nice little parting gift and last words created an archnemesis for Wolverine that would go on to menace him and everyone around him for the rest of his life. And they're both immortal.
* In ''ComicBook/TheMultiversity'', Ultra Comics is [[spoiler:exploited by the Gentry as a means to infiltrate the multiverse]]. While he manages to [[spoiler:seal Earth-33 off from them]], he's ultimately unsuccessful in [[spoiler:defeating the villains]].
* The race known as the [[ComicBook/GreenLantern Guardians of the Universe]] practically has this as its ''[[PlanetOfHats hat]]''.
** One member of their race, attempting to settle the Origin Question (basically, why is there a universe and why is there life in it and specifically why are there Oans/Malthusians in it), [[ComicBook/CrisisOnInfiniteEarths introduced Evil (or at least Entropy) into the universe]].
** To combat evil, they formed a corps of robotic police called the Manhunters. That didn't work out so well.
** To combat evil ''and'' the Manhunters, they decided that another Corps was the way to go, this time the Green Lantern Corps. Noble in principle, but they also decided to [[SealedEvilInACan seal the Fear Entity inside the artifact giving the Green Lanterns their power]]. That [[ComicBook/ZeroHour didn't work out so well either]].
** Really, anytime something in the DC Universe is going very badly on a cosmic scale, the Justice League could save themselves some detective work by starting with the assumption that it's at least related to something that either Darkseid did on purpose or the Guardians did by accident.
[[/folder]]

[[folder:Fan Works]]
* In ''Fanfic/MarieDSuesseAndTheMysteryNewPirateAge'', [[spoiler:Eustass Kid wonders aloud in front of Madelyn what would happen if the Straw Hats were delayed, making it possible for the Kid and Heart Pirates to compete for One Piece.]] The "unwitting" part comes from the fact that he doesn't realize [[spoiler:Madelyn, with her powers]] could make this happen, or that she would want to. [[spoiler:Madelyn then concludes that Law has lost his spirit for pursuing One Piece because he thinks Luffy will win, and then wishes for him to get captured to force his crew to go after him; this ends with Luffy's execution and the deaths of all the other Straw Hat pirates, among other events.]]
* While most ''Fanfic/ImperfectMetamorphosis'' readers quite rightly blame Team 9 for nearly everything, they couldn't have even stolen [[spoiler:Rin Satuski's]] [[SealedEvilInACan can]] in the first place if Marisa hadn't stolen it from Patchouli. Marisa's StickyFingers are the only reason anything in the story happened.
* Back in the original series, Yamada Tatsumori/Aries Zodiarts was the one who instigated the DealWithTheDevil with Ryusei so Ryusei could revive his friend. What happens in ''FanFic/HorseshoesAndHandGrenades''? The deal with Gentaro dead gave Ophiuchus a way to wreak his havoc on the world (and bring in other Serpents for the ride) and having nearly ''every'' named character from Fourze involved in multiple adventures to stop Gamou's advent of injecting former Switchers with Cosmic Energy, the origins as to why Ophiuchus is causing this madness and Ryusei being brainwashed and transformed into a cyborg. Didn't think this through, did you, Apostle of Sleep?
** Ryusei also should be blamed for killing Gentaro in the first place considering that Tachibana had stated that there was an alternate and ''safer'' way to bring Jiro back to life.
* In ''Fanfic/BoysUndSenshado'', two pop up in [[WhamEpisode Chapter 6, with consequences for Chapter 7]]. The gunner of the Semovente [[spoiler:shoots Miho by accident]]. In the ensuing chaos, Mako almost makes the mistake of [[spoiler:running over Miho]]. Miho, while [[DisappointedInYou disappointed in Mako]], refuses to punish her, which results in Miho's mother [[spoiler:disowning her]].
* Twilight Sparkle in FanFic/DividedRainbow, for causing the {{Swap|pedRoles}}.
* [[spoiler:TCB!Lyra Heartstrings]] is revealed to be this in ''Fanfic/TheConversionBureauTheOtherSideOfTheSpectrum''. [[ForWantOfANail It turns out]] that the reason why the MirrorUniverse Equestria turned into [[TheEmpire the Solar Empire]] and is carrying out its [[AssimilationPlot ponification crusade]] against humanity is all because [[spoiler:she went on a scuba diving trip with some friends where she happened upon the sunken ship of the KV-62 Archaeological Party coming from [[WesternAnimation/MyLittlePonyTVSpecials Dream Valley]]. Unfortunately, she also found the [[ArtifactofDoom Bag of Tirek]], which seeks to carry its maker's will out by enslaving every living being in existence and targeted humanity first [[DisproportionateRetribution out of revenge]] because Tirek himself had been by a human in the past]]. However, it's also heavily implied that she was just as much an UnwittingPawn too.
* ''FanFic/RosarioVampireBrightestDarkness'':
** As revealed in Act III chapter 15, while making Yukari a new wand, Apoch and Astreal misread the instructions to do so and make her the [[EvilWeapon wrong one]]. As a result, Yukari gets DrunkWithPower and tries to kill the gang in a fit of rage, causing Tsukune to break ''two'' more links on his [[RestrainingBolt Holy Lock]] in order to stop her and destroy the wand. All of that chaos happened simply because Apoch and Astreal misread an instruction booklet.
** It's also revealed over the course of Act III that Kenzo had had one of his men follow Dark the night he hid Felucia's [[SoulJar spirit artifact]] to ensure it was in a safe place. While he was well-intentioned at first, [[spoiler: Hokuto finds this out and sends Kuyou after Kenzo in order to discover its location. The end result: Kenzo ends up dead by Kuyou's hands, and Hokuto gets his hands on Felucia's spirit artifact and uses it to extort Felucia into being his minion]].
* From the later parts of ''Gensokyo20XX'', we have an age-regressed Reimu, who was conditioned not to sense danger. This is especially so in 20XXIV, when she crawls out of the house right into danger, which has Ran almost raped by another male kitsune. From 20XXV, we have the unknown and unnamed tenant who left rat poison where the aforementioned could get it and it leading to her suffering brain damage in the aftermath.
* In ''FanFic/TheVow'', while in sad and angry stupor over [[spoiler:his wife's death]], [[{{Jerkass}} Lord Chang]] claims [[WesternAnimation/KungFuPanda2 Shen]] that he's only living in his parents' shadow and the history shall never remember him for great achievements. Haunted by those words, Shen ends up accidentally inventing black powder, starting his canon dark path.
[[/folder]]

[[folder:Films -- Animation]]
* P.T. Flea from ''WesternAnimation/ABugsLife'' got Flik and the circus bugs ostracized by the colony and then later in the film incinerated a fake bird, thinking it was the real deal. Earlier in the film he had also fired the circus bugs, leading to them meeting Flik and setting the plot in motion.
* Both Gringoire and Djali serve as this in the Burbank Films Australia [[WesternAnimation/TheHunchbackOfNotreDameBurbankAnimation adaptation]] of TheHunchbackOfNotreDame - firstly, Gringoire tells Frollo where Esmeralda is going, thus allowing the priest to find and stab Phoebus, then Djali performs a trick during Esmeralda's trial, thus "proving" the accusations of witchcraft. Luckily, disaster is averted when Quasimodo rescues Esmeralda.
* In ''WesternAnimation/TheIncredibles'', Buddy Pine is to blame for the FrivolousLawsuit, SuperRegistrationAct and everyone being forced into hiding. But in the end he makes the Supers re-emerge and being hold as heroes again, thanks to his failed scheme.
* Hot Rod was a borderline TheLoad during the fight between Optimus Prime and Megatron in ''TransformersTheMovie''. He promptly was hostage by Megatron, resulting in Optimus's death.
* In ''WesternAnimation/KungFuPanda'', Shifu's goose messenger to Tai Lung's prison gives him both the means to escape and the motivation to do so. Blame is also placed on the prison commander for dislodging the feather Tai Lung used to escape.
* ''Disney/WreckItRalph'': If Gene hadn't goaded Ralph into getting a medal, many, ''many'' problems could have been avoided. [[InvertedTrope On the other hand]], [[spoiler:no one would have discovered a dark secret about Sugar Rush either]].
* The whole main plot of ''Disney/{{Frozen}}'' is caused by Hans' horse. It knocked into Anna, [[CrashIntoHello prompting her and Hans' meeting]], which led to their engagement, which led to Elsa's bout of PowerIncontinence and her panicking, fleeing, and burying Arendelle in snow. [[spoiler:Of course, given what we learn of Hans later in the film, he may have arranged most of this; though he didn't know about [[PersonOfMassDestruction Elsa's powers]] [[PowerIncontinence before they were revealed]], [[LetNoCrisisGoToWaste he did his best to take advantage of the opportunities that arose]].]]
** Not helped by the fact that most of her emotional duress (as well as Anna's social awkwardness [[spoiler:that Hans exploits]]) were the result of her parents shutting them away from the world in an attempt to control her powers, when really they just hid them and never focused on helping her learn to control them.
* In ''WesternAnimation/{{Home}}'', [[spoiler:during an attempted peace conference with the Gorg, Captain Smek ran and grabbed a small rock on the way out, placing it on his "shusher wand." It is later revealed that the rock actually contains the next generation of Gorg, which is the true reason the Gorg has been chasing the Boov]].
[[/folder]]

[[folder:Films -- Live Action]]
* ''Franchise/StarWars'':
** In ''Film/ANewHope'', the Star Destroyer officer who orders his subordinate not to fire on the escape pod containing C-3PO and R2-D2, thus ensuring that Luke Skywalker gets Princess Leia's message and brings about the end of the Empire. If this nameless officer had not been so frugal with laser ammo, TheDarkSide would surely have triumphed.
** In ''Film/AttackOfTheClones'', the one thing that [[TheScrappy Jar Jar]] actually does in the movie, other than [[DemotedToExtra stand in the background]], is to make a motion in the Senate to grant Palpatine emergency powers. Yes, ''[[BigBad that]]'' [[MagnificentBastard Palpatine]]. Jar Jar was already so despised at this point that the reaction was mostly along the lines of "He was the cause of all the evil in the universe? ''I knew it!''"
** If Admiral Ozzel in ''Film/TheEmpireStrikesBack'' hadn't been so impetuous and exited hyperspace too close to Hoth, the Rebels wouldn't have had time to set up the shield generator and the Imperial fleet could have just bombed them form orbit. This leads to the trope namer for YouHaveFailedMe.
** Wicket in ''Film/ReturnOfTheJedi'' is the only reason the Rebels won. If he didn't pull a BigDamnHeroes moment by bringing [[RockBeatsLaser an army of Ewoks to fight the Imperials]], the Rebels would never have destroyed the shield generator and never would have destroyed the second Death Star. The Rebels only met the Ewoks at all because of a Scout Trooper who knocked Leia off of her speeder bike, leading to her befriending them while the others searched for her. If he had aimed a little higher, none of the above would have happened (how appropriate that the Empire's downfall is ultimately caused by the ImperialStormtrooperMarksmanshipAcademy).
** Anakin is the Instigator of his own doom. If he hadn't finished that protocol droid he had started in ''The Phantom Menace'', things could have been very different. One possible unfolding: R2-D2 would have never been sold to the Lars family without C-3P0's endorsement, thus R2 stays with the Jawas, R2 gets vaporized when the detachment of Stormtroopers find the sandcrawler, and Leia's message never reaches Obi-Wan.
** Darth Maul, for all [[EnsembleDarkhorse his popularity]], does precisely one thing in ''Film/ThePhantomMenace'': kill Qui-Gon Jinn. Except that by doing so he ensures Anakin is taught by a newly-Knighted Jedi instead of a wise Master with decades of teaching experience, which plays a huge role in his frustration with the Jedi Order and inability to deal with his phenomenal powers, which in turn plays a huge role in his FaceHeelTurn.
* In the Kevin Costner version of ''RobinHood'', his blind manservant Duncan gallops into Sherwood Forest in order to tell his master that Marian has been captured by the Sheriff; only for the bad guys to follow him straight to the outlaws' hideaway and start to massacre everyone there. Beyond getting ushered about by either Robin or Marian, it's the only thing he ever does in the movie.
* In ''Film/WrongTurn4BloodyBeginnings'', a prequel to the ''Film/WrongTurn'' series, one of the characters beg someone not to kill the inbreeds. They spare their life, but in return are responsible for nearly ''every single death'' in the films.
* In ''Film/TheLordOfTheRings: The Two Towers'', at least in the film version, Faramir is one. He is prepared to shoot and kill Sméagol for entering the Forbidden Pool and seemingly allows Frodo to call him out of the pool, but immediately captures him upon his exit. Sméagol thinks Frodo lied to him and, enraged by this apparent betrayal, regresses into his Gollum persona and starts plotting his and Sam's deaths for the sake of retrieving the Ring. In the director's cut, the honor goes to Sam: he spends the whole movie antagonizing the old ring bearer, so when he tries to explain to him at the end that his capture was not Frodo's decision, Sméagold is quite obviously unconvinced.
* In ''Film/TheEliteSquad'', there's the unknown journalist who takes a photo of Matias and inadvertently reveals the fact that he's a cop to the drug dealers. It ruins Matias's relationship and leads to another character's death.
* The Creator/ShirleyMacLaine comedy ''Film/WhatAWayToGo'' could alternately have been titled ''Unwitting Instigator Of Doom: The Movie'', with [=MacLaine's=] character being widowed four times after her entirely well-meaning suggestions inevitably, relentlessly, snowball into her current husband getting killed in some bizarre fashion.
* In ''Film/XMenDaysOfFuturePast'', Mystique's plan was simply to avenge a number of dead mutants by killing the man who had experimented with their corpses. That man had projects, rejected by the Congress, to build powerful robots to kill mutants. His death proved his point, that mutants were an actual menace, and so his projects were restored and continued. The Sentinels would prove so deadly and effective that they would cause the apocalyptic future seen at the beginning of the story. Of course, Mystique had never intended any of that, all she wanted was some basic and plain revenge.
* In AkiraKurosawa's ''Film/TheBadSleepWell'', Nishi's revenge plot is scuppered by his father's well-meaning widow, who innocently reveals his real identity to one of the men Nishi wants to destroy.
* In ''Film/ANightmareOnElmStreet4TheDreamMaster'', Elaine Parker not only was responsible for her daughter Kristen's death (she put sleeping pills in Kristen's drink), but thanks to that happening it gave Freddy the opportunity he needed to successfully establish a link to the rest of Springwood's teen populace. So basically every death from this movie onward is because of her. Nice job, Elaine.
[[/folder]]

[[folder:Literature]]
* In the former trope-naming incident, from the Literature/SherlockHolmes story ''The Final Problem'', a Swiss messenger in Moriarty's employ catches up to Holmes and Watson with a message saying that an Englishwoman at the hotel they're staying at is on the verge of death and wants to see an English doctor. Watson obediently returns to the hotel, unknowingly [[spoiler:leaving Holmes to face Moriarty alone at the edge of Reichenbach Falls, apparently leading to both of them falling to their death]]. However, it is implied that [[spoiler:Holmes knew all along what was going down but saw no reason to put Watson at further risk.]]
* Catelyn Stark in ''ASongOfIceAndFire''. ''Twice'', but [[spoiler:releasing valuable prisoner Jaime Lannister in an attempt to get her daughters back from the Lannisters]] is more cited than [[spoiler:kidnapping Tyrion Lannister, believing him responsible for the attempted murder of her son on the word of her UnluckyChildhoodFriend Petyr Baelish]], Despite the fact that the Tyrion incident was the casus belli of the civil war that has made the entire world turn to shit ever since.
** Fans often cite [[spoiler:the release of Jaime]] as a crucial step leading up to the Red Wedding, but there are parts of the text suggesting that said wedding was already being planned before it happened. Both Lord Tywin Lannister and the Starks's [[spoiler: treacherous ally Lord Roose Bolton]] appear to be planning something around the time of his release.
*** For that matter, Rob perhaps would have kept his word to the Freys thus negating the whole need for a Red Wedding if he hadn't grown up seeing his otherwise loving mother turn into an EvilStepmother around the [[HeroicBastard sole proof of her husband's infidelity]].
** The irony of Catelyn is that, in most other fantasy worlds, she and Ned would be the most sympathetic characters in the entire story, and the clear virtuous protagonists of the piece. In the CrapsackWorld that they live in, though, they are either directly or indirectly the cause of something like 90% of the tragedy that follows.
** Also Sansa Stark with the whole Lady affair, or running off to Cersei when she did. Forgiven by many only because of [[TheWoobie what happened to]] [[BastardUnderstudy her after that.]]
** When she was a girl, Lysa Tully was in love with her father's ward Petyr Baelish, who was light-years below her in social status so a marriage was impossible. Also, he was in love with her older sister Catelyn. So one night after watching Petyr dance with Cat and get very drunk after Cat wouldn't kiss him, [[spoiler:Lysa crept into Petyr's bed in the dark and had sex with him. She told him she loved him and wanted to marry him, while letting him think she was Cat]]. Shortly after this, Cat's [[ArrangedMarriage engagement]] to Brandon Stark was announced and (understandably from his point of view) Petyr challenged him. Short scrawny 15-year-old Petyr nearly died fighting tall strong 20-year-old Brandon and was promptly thrown out for this and for [[spoiler:getting Lysa pregnant]]. This humiliation was Petyr's StartOfDarkness, turning him into the villain responsible for [[spoiler:the entire civil war - with Lysa manipulated into lighting the first fuse]]. Well done, Lysa!
* ''Literature/HarryPotter'':
** Bertha Jorkins in Book 4. Doesn't appear 'on-screen', doesn't have any speaking roles, dies long before Book 4, but is absolutely crucial in giving the BigBad the capacity to put together his EvilPlan for the book- [[spoiler:she worked for the Ministry's Sports Department, so she knew about the Triwizard Tournement. She then went on holiday to Albania, where Voldemort was lying low with Wormtail. She happened to bump into Wormtail and recognised him, and then she was subjected to lots of tortures and MindRape to make her a source of information to Voldemort. It didn't help that she had coincidentally discovered Barty Crouch Jr.'s existence, either.]]
** Marietta Edgecombe. She revealed the existence of Dumbledore's Army, thus leading to Dumbledore having to flee Hogwarts and Umbridge taking over. [[spoiler:This also indirectly led to Sirius's death, because had Dumbledore remained at Hogwarts, when Harry had that dream about Sirius being captured by the Death Eaters, he would have gone to ''him'', instead of playing into Voldemort's hands. [[ArsonMurderAndJaywalking It was also a key factor in Harry's breakup with Cho Chang.]]]]
** Remus Lupin in ''Prisoner of Azkaban''. [[spoiler: If he'd remembered to take his potion before the climactic confrontation, he wouldn't have been a threat when he became a werewolf, and could have continued to concentrate on keeping Pettigrew from getting away. And if Pettigrew hadn't gotten away, and had been turned in to the authorities, Sirius would have been cleared of his murder charges and would no longer have to be a fugitive, meaning he could have a closer relationship with Harry. And if he'd had a closer relationship with Harry, Voldemort wouldn't be able to use their separation to trick Harry, and Sirius wouldn't have ended up dead.]]
* In ''Literature/BattleRoyale'', [[spoiler:just as Shinji is about to pull off his plan to escape the Program, a fellow student, Keita Iijima, shows up, oblivious to what's going on, and accidentally ruins the entire plan, getting everyone involved killed.]]
* ''Literature/CatsCradle'' has whoever failed to perform proper maintenance on the fighter plane which crashed into the side of the castle.
* Lucy's mother in {{Dracula}} is partly responsible for killing Lucy by [[spoiler:opening the window and removing the garlic so that Dracula can get into the room]].
* In ''TheWiseMansFear'', [[TheDreaded The Cbaeth]] creates these by acting as a malicious oracle or saving peoples' lives.
* Jacob in ''TheRedTent'' Because he demands an outrageous bride price for his daughter (after a [[DoesNotUnderstandSarcasm sarcastic]] comment by Joseph), because of a combination of greed and OverprotectiveDad factor, his sons murder Dinah's TrueLove, and all the other Shechemite men. Jacob [[WhatTheHellHero calls his sons out on it]] and dies [[MyGodWhatHaveIDone full of regrets]].
* Curley's wife from ''Literature/OfMiceAndMen'' wanted to have a friendly conversation with Lennie, despite George's orders to Lennie to stay away from her. She eventually took advantage of Lennie's fondness for soft things, and offered Lennie to touch her hair; this soon led up to Curley's wife getting scared and beginning to scream, which in turn made Lennie scared that George would hear her so he squeezed her hair tighter. Guess who winds up with her neck broken. The death of Curley's wife quickly led up to the novel becoming a ShootTheShaggyDogStory.
* Inverted in the ''StarWars'' novel ''Literature/DeathStar.'' Two utterly trivial characters from the first film (the guard who says, "Close the blast doors!" too late, and the gunner who says "Stand by... stand by....") turn out to have [[spoiler:chosen to let Han Solo and Chewie get away, and chosen not to fire on Yavin, because they'd started to have doubts about the Empire. If not for them, the Rebellion would have been crushed.]]
* ''InDeath'': This trope has happened a few times. ''Vengeance In Death'' had a brilliant plan to catch the murderer ruined by a robot poodle that caused a chain reaction of events that caused the cops to reveal themselves and for the murderer to spot them and run for it. ''New York To Dallas'' contains two instances of this. The first one had a brilliant plan to catch the murderer's partner ruined by a dog that caused a kid to almost get run over by a car, a cop having to save the boy's life and reveal himself as cop, causing the murderer's partner to spot them and run for it. That instance got subverted by the partner getting caught despite a chase anyway. The second instance had the cops closing in on the murderer, only for the murderer to get away. How? The murderer was out shopping when he overheard a conversation between staff member and a stock boy about cops. The staff member recognized an undercover cop working in the area and he was just telling the stock boy about how this cop came to a criminology class and how cool he is. The murderer naturally chose to run for it. Clearly these minor characters would not get a lot of sympathy from readers.
* In ''Franchise/{{Halo}}'' ''Contact Harvest'', negotiations between Humanity and the Covenant are taking a nasty direction (the Brutes demanded the Earth and everything on it, humans said no). A frightened Grunt attacks a Marine, an act that triggers the entire Human-Covenant War and everything connected to it. The Halos, the Forerunners, the Flood, the Spartans like Master Chief -- it's possible none of them would have been discovered or created if that Grunt had been less impulsive.
** ''The Kilo Five Trilogy'' has ONI's leader Admiral Parangosky, who went behind UNSC's leadership to instigate a civil war among the Elites, in hopes of tipping the scales to the UNSC's favor. By Halo 4 however, all of their actions cause more harm than good. The renegade Elites instead become willing followers to The Diadacts cause of eradicating humanity.
* ''Literature/CiaphasCain'', HERO OF THE IMPERIUM, has his own personal version of this trope in Toren Divas who manages to be both his best and [[TheFriendNobodyLikes most hated]] friend. The best example is in the starship at the start of ''Death or Glory'': while Cain and Jurgen struggle to get out of a room where the hull has been breached, Divas' attempts at being over-dramatic knock some guardsmen off balance as they hold open the emergency doors, trapping Cain and Jurgen and forcing them to get into a lifepod, making planetfall deep in ork-held territory. This sets off the whole plot, though as that involved Cain and Jurgen's flight to safety snowballing into liberating the planet, the people of Perlia would probably have thanked him.
* Literature/TrappedOnDraconica: Yusef tells Gothon where the Eastern Alliance's HQ is and how to defeat their army. He thinks this will lead end the war with minimum casualites on both sides. This is his only action in the entire story.
* ''Literature/TheHitchhikersGuideToTheGalaxy1'' contains Arthur Dent making a comment about his difficult lifestyle... that gets sucked through time and space to the conference table of two armies, is interpreted in their language as the worst thing to ever say, and ultimately sparks a thousands-of-years-long war between the two that devastates all in its path and kills thousands. Then the two realise the problem and [[EnemyMine team up to attack the Earth]] [[spoiler:where they are promptly eaten by a dog]]. Indeed, this sort of thing is hinted by the book to happen all the time, potentially making ''everyone'' this trope.
* In ''Literature/TheLastBattle'' Shift the Ape and Puzzle the Donkey find a lion skin in the waters of Caldron Pool, which leads to the former convincing the latter to dress up in it and pose as Aslan. Their actions kick-start the End of Narnia, but the source of the lion skin is casually mentioned as being a hunter up in the Western Wilds who killed and skinned a lion weeks before.
* Supreme Chancellor of the Republic Tarsus Valorum in the [[Literature/DarthBane Darth Bane trilogy]] ended up doing this. After the New Sith Wars ended with the Battle of Rusaan, he passes the Ruusan Reformations, which among other things disbands the Republic's military and also forces the Jedi to take a more advisory role in the Republic rather than the protectors that they used to be. This would later play into Palpatine's hands when he took advantage of Jedi Master Sifo-Dyas's contracted clone army to create an army unquestionably loyal to him, rather than thinking men that might form their own opinions. He facilitated the rise of the Empire a thousand years later, though he couldn't have known it at the time.
[[/folder]]

[[folder:Live Action TV]]
* ''{{Buffyverse}}'':
** Wesley in ''Buffy'' overheard that Faith accidentally killed someone. The rest of the team is already on-board with helping her deal with her issues and giving her the support and acceptance she needs in order to not fall to TheDarkSide. Wesley's response on the other hand is to call in some goons and try to ship her to England to be locked away forever. By the end of the episode, she doesn't trust any of them, resents all of them (because she thinks they want her to just be like Buffy), and has taken a job as the BigBad's [[TheDragon number two]].
** Angel. Wolfram & Hart has a stated mission of bringing Angel to their side. Sound pretty far-fetched? The road to Hell is paved with good intentions.
* In the second season of ''Series/CriminalMinds'', [[spoiler:the team was trying to bring in a delusional war veteran who is panicking because the construction sounds like the war zone. Now, they find him and have swat surround the suspect as they coaxed him to surrender. They tell these construction men nearby in plain view of the drama to stop working until they are done, but naturally the men resume construction before the suspect is apprehended. This causes the suspect to panic and he runs towards a kid on a bike, forcing a SWAT marksman to shoot him.]] [[WhatTheHellTownspeople The construction crew couldn’t have waited 30 minutes for the damn police, SWAT, and FBI to finish?]]
* ''Series/DegrassiTheNextGeneration'' gives us Paige Michalchuk, who gets her friend Terri drunk before a dance and ends up with the guy Terri wanted instead. Later on, Terri thinks she'll never find a man and ends up with abusive boyfriend Rick. Later, Rick comes back and Paige gets to be an inversion of this trope, albeit ultimately subverted because someone else pisses Rick off enough that he starts shooting people.
* In murder mystery ''HarpersIsland'', nine-year-old Madison is kidnapped by the AxCrazy BigBad, John Wakefield. When rescued, she goes along with the lies Wakefield told her to tell the others -- specifically that it was the Sheriff who kidnapped her. ''Even though she knew that Wakefield was evil.'' This gets several people killed and Madison became TheScrappy.
* Narrowly {{averted}} by Princess Mithian on ''Series/{{Merlin}}'', who in a bid to impress KingArthur, shoots a young deer in the forest. Unbeknownst to her, the deer is actually [[BalefulPolymorph Guinevere under an enchantment]]. Only Merlin realizes what she's done and returns to the forest at night to hunt for Gwen and heal her from her injury.
* ''Series/PowerRangersRPM'': To escape from the research facility she spent most of her pre-series life confined to, Doctor K decided to release a sentient computer virus her captors had her design for them. She intended to keep it to the facility's computers, but two guards caught her before she could finish installing the firewall, ignoring all her protests. Cue the destruction of human civilization outside of Corinth City. In ''Power Rangers''.
* Due to a lot of TimeTravel and AnachronicOrder being involved, the Blue Senturion in ''Series/PowerRangersTurbo'' is often accused of being this, the negative result being Zordon's death. He'd come back in time a thousand years to warn of a massive war a year later -- but the villains intercepted him, took the message, then wiped it from his memory, resulting in the evil side of the war being ''way'' more prepared than the good guys.
** Of course, time travel being what it is, no one really knows how different the end result would have been.
* In the BBC's ''Series/RobinHood'' the titular character is trying to make a tentative alliance with Isabella, the new Sheriff of Nottingham (and his ex-girlfriend) despite the grumblings of the other outlaws. His reasoning is sound, and after striking a deal with her he asks Little John to escort her safely home. For no reason whatsoever, John decides to tell Isabella that Robin "has eyes for [[TheScrappy Kate]]" (a fellow outlaw). This achieves nothing except [[GreenEyedMonster pissing Isabella off]] and [[IHaveBoobsYouMustObey leading her to doubt that she has any kind of power over Robin]]. She turns on him at the next available opportunity which leads directly to two outlaws' deaths. [[NiceJobBreakingItHero Nice job antagonising]] the valuable ally, John.
* Octavia in ''Series/{{Rome}}'' may have been indirectly responsible for the deaths of Julius Caesar and [[spoiler:Vorenus' wife. Octavian told her about Vorenus' wife's affair and told her it was a secret. For no reason whatsoever, Octavia told Servilla this. When Caesar's enemies planned to assassinate him, this information became crucial and was used to drive Vorenus (who was supposed to guard Caesar) away, leaving Caesar as a sitting duck. Meanwhile, Vorenus confronted his wife and she ended up killing herself out of honor.]] And of course, there is the whole second round of war and murder until it is settled who succeeds Caesar, which ends with the establishment of TheEmpire.
* ''Series/OnceUponATime'':
** Baelfire is one of the main causes of the plot in the show. His father Rumpelstiltskin became the Dark One to protect him from becoming a child soldier. [[spoiler:His disappearance into another world]] is what caused Rumpelstiltskin to search for a land without magic - and so create a curse dooming the entire populations of multiple worlds to years of misery. All of Rumple's deals and schemes, including turning Regina Mils into a "monster," was part of his plan to [[spoiler:find Baelfire.]]
** Also, Queen Eva started the bitter and long feud between Cora, Regina and Snow's family because when she was young and a SpoiledBrat, [[spoiler:she exposed Cora as an unwed mother to keep her fiancee King Leopold from marrying her. Then she tripped Cora, claimed that Cora hurt her, and thus began Cora's long vendetta against the nobles and in particular, her family.]]
** In the first season finale, Jefferson decides to [[TheDogBitesBack get revenge on Regina]] by exploiting Rumpelstiltskin's love for Belle. In doing so, [[spoiler:Rumpelstiltskin sends the Wraith against Regina in his ''own'' revenge which results in it (along with Emma and Mary) to be banished to the Enchanted Forest. The following events led to [[BiggerBad Cora]] finding her way to the real world and set off almost all the events of Season 2, and by extension, the rest of the series.]]
** Mr. Gold's [[KickTheSonOfABitch pursuit for revenge at the end of season 3]] winds up severing the ties with that arc's BigBad and her AmplifierArtifact. This results in the magic triggering her [[spoiler:TimeTravel spell which got Emma and Hook trapped in the past where they, [[NiceJobBreakingItHero along with several other things]], end up bringing with them a golden urn that spills over and creates the next BigBad: The Snow Queen. Thus, Season 4's plot begins]].
** The season 4 crossover arc with ''Disney/{{Frozen}}'' is another case, according to the episode "The Snow Queen". Basically, the Duke of Weselton tried to seduce his betrothed Helga's sister Ingrid. This caused Helga to be killed by Ingrid, which causes Ingrid's other sister Gerda to develop a fear of her family's magic, which led to her and her husband seeking to find a way to treat Elsa's magic, and caused the events of the movie to happen and the events of the ''Frozen/OUAT'' crossover to happen.
* A particularly heartbreaking episode of ''ColdCase'' gave us a girl who had a crush on the VictimOfTheWeek, who was a mentally-challenged teenager. One day alone in class, she tried to kiss him when her [[BastardBoyfriend meathead boyfriend]] walked in and she lied and said ''he'' tried to sexually assault ''her'' so that she wouldn't get a "bad reputation", which essentially caused him to be beaten up by the said boyfriend and his gang of thugs (as well as him only friend, who was embarrassed by him), her parents deciding to file charges against him, he ending up in an institute instead where, due to his alleged sexual deviance, is in the worst tier of the facility where the care for the patients is horrifyingly neglectful, quite frankly. In addition to this, the boy's loving mother (and one of only two people at this point who gave a damn about him) is dying of cancer as all of this is occurring, the boy's [[JerkAss father won't take care of him because of his mental status]] and the boy's [[spoiler:caregiver, who was also dating the mother, takes him from the institute and [[TearJerker rather than have him live a life of loneliness and neglect, has him ran over by a train.]]]] In present day, the girl FINALLY realizes the effect of her actions and is remorseful, but it's still too little, ''way'' too late.
* In ''Series/StarTrekDeepSpaceNine'' Kai Opaka gives Commander Ben Sisko one of the Tears of the Prophets and asks him to find the Celestial Temple to help reunite the Bajoran people. What she didn't realize was that the Celestial Temple was actually a wormhole to the other side of the galaxy. Its discovery by the Federation lead to disastrous first contact with [[TheEmpire the Dominion]] and eventually the most devastating galactic war of the Trek verse.
[[/folder]]

[[folder:Professional Wrestling]]
* Wrestling/ChrisHero was kicked out of Wrestling/{{Chikara}} in 2007 and all relating to him [[UnPerson was scrubbed clean from view]] but his actions continued to have an effect on the promotion regardless. It was his acquisition of the Eye Of Tyr from Dr. Cube of Wrestling/KaijuBigBattel that allowed for Wrestling/UltraMantisBlack's Order Of The Neo Solar Temple to gain power and the BDK after them, and [[Wrestling/HunterJohnston Delirious]] taking up the ways of a rudo after that, and [[Wrestling/{{Hallowicked}} the]] [[Wrestling/{{Frightmare}} rest]] of Incoherence going bad after that. The effects of manipulations also lead to the rise of STIGMA in his absence.[[/folder]]

[[folder:Sports]]
* [[http://en.wikipedia.org/wiki/Fred_Merkle Fred Merkle]]. Had ThisWiki existed one hundred years ago, no further explanation would have been needed. Basically, Merkle was a baseball player for the Giants back in the early twentieth century. In the bottom of the ninth inning in a game against the Cubs, there were two outs and the score was tied, and Merkle was on first base (someone else was on third). Another player scored, scoring a game-winning run, but in the excitement Merkle never actually stepped on second base. Thus, a player for the Cubs stepped on second base and called Merkle out, thus nullifying the run. As this game was played before electric lighting, the game was declared a tie. Thus, the Giants and Cubs ended the season tied for first place, requiring a rematch to determine who would go on to win the pennant. The Cubs won. The sheer amount of hatred directed at Merkle's one mistake was astounding, especially considering that he was far from the only person who cost the Giants the pennant.
** It wasn't excitement that kept Merkle from stepping on second; the fans stormed the field, and he ran for the clubhouse for his own safety. The game was called a tie after the Cubs player somehow made the play in that mess because they couldn't clear the field. It should also be noted that, since this behavior by the fans was quite common back then, such a force out had never before been enforced under those conditions. All of this really makes Merkle one of the worst cases of MisBlamed in sports history.
*** And we'll all forever HaveAGayOldTime out of that one ("Merkle's ''Boner''", anyone?).
* Steve Bartman. As the story goes, the Chicago Cubs were on their way to their first World Series since 1945 when hapless fan Bartman interfered with a foul ball, costing the team a precious out. What gets overlooked is that after the incident, Chicago still led 3-0 with one out in the 8th inning, and could have easily won the game if not for a bout of spectacular incompetence: a wild pitch, an error on an easy ground ball that could have ended the inning, two intentional walks that backfired to the tune of four runs allowed, and other hard hits. The tense 3-0 game became an 8-3 laugher. Oh, and that was only Game 6 of a seven-game series; the Cubs could have still made the World Series by winning Game 7, at home, with their best pitcher going. That didn't work out either.
* Similarly, Bill Buckner's epic error in 1986. History notes that the Red Sox had the Mets down to their final out, and three times down to a final ''strike'' that would have brought Boston a long-awaited championship. Buckner's famous gaffe was made possible only by three consecutive singles, a wild pitch, and pitcher Bob Stanley failing to recognize that baserunner Ray Knight had strayed so far from second base he could have been picked off easily. And, like the above example, this loss only tied the series at 3-3; the stunned team could have regrouped and won the next day, but did not. Furthermore, the game was tied (due to the wild pitch mentioned above) when Buckner made the game-ending error. Had he made the play, the game would have continued another inning, making this another case of MisBlamed.
* In the bottom of the ninth inning of game six of the 1985 World Series, umpire Don Denkinger called Kansas City Royals baserunner Jorge Orta safe on a close play at first base. ABC's replay showed that St. Louis Cardinals pitcher Todd Worrell managed to get to first base and took the toss from first baseman Jack Clark at the base before Orta reached it. Cardinals fans will blame this call for costing them the championship and Denkinger was hounded by them for years. However, Orta was the first batter of the inning. The Royals eventually loaded the bases and it was the fourth batter of the inning, pinch-hitter Dane Iorg, who got the hit that scored two runs to give Kansas City a 2-1 victory. The Cardinals could have still won the series the next night in game seven, but were still unhinged by the events of the previous night and the Royals won 11-0, claiming the only World Series title the team has ever won. It didn't help that the Cardinals had won the first two games of the series in Kansas City and held a 3-1 lead in the series after five games, making the Royals the first team ever to come back from a 3-1 series deficit after losing the first two games at home. Oh, and Orta wasn't even on base when the winning run was scored...he was thrown out at third on a poorly-executed bunt play.[[note]]This ''also'' ignores the fact that the Cardinals had already benefited from a similar bad call: Royals player Frank White was called out in a close play at second but the replay showed that he, unlike Orta, had actually beaten the tag; the next hitter, Pat Sheridan, drove a single to right field that likely would have allowed White to score from second, more than making up for Orta's scoreless two-base advance.[[/note]]
** In general, if there's any kind of controversial call that results in a team missing a chance to score (or stop the opponents from scoring), resulting in that team losing, the referees will usually be blamed for the loss, even if the players could have avoided the game even being that close in the first place.
* For all the flack Lebron James got for the Miami Heat losing the 2011 NBA Championship. it may have been Dwayne Wade that started the collapse. Miami looked to have a 2-0 lead over Dallas when Wade hit a three-pointer to put them up by 15 in the fourth - and he chose to taunt the Mavericks by posing in front of their bench. Dallas mounted a furious rally to win that game, posted another comeback in Game Four and ultimately took the trophy right from under the anointed Heat's collective noses.
* From the American point of view, an unidentified member of the Illinois Highway Patrol [[http://espn.go.com/golf/rydercup12/story/_/id/8444955/2012-ryder-cup-rory-mcilroy-needs-ride-police-make-tee-time who escorted the Northern Irish World Champion golfer Rory McIlroy]] to the final day of the Ryder Cup; [=McIlroy=] was instrumental in Europe's comeback from 6-10 to retain the cup 14.5-13.5.
[[/folder]]

[[folder:Tabletop Games]]
* ''TabletopGame/MagicTheGathering'': Lamar, a barbarian sentry from ''[[Literature/OdysseyCycle Judgment]]'' who sees Jeska knocking Kamahl's friend Balthor unconscious, and, believing she's killed him, rushes to tell Kamahl, who [[spoiler:[[PoorCommunicationKills attacks Jeska in a fit of rage, mortally wounding her]]]]. This leads to the Cabal finding Jeska and [[ReforgedIntoAMinion saving her life by transforming her into Phage the Untouchable]], kicking off the apocalyptic events of the entire ''Literature/OnslaughtCycle''. Which, as it turns out, led to the fabric of existence being marred so much that temporal rifts began opening across all of the Multiverse (at various points in spacetime, no less); these rifts were revealed to be the causes of some key events that led to the Kamigawa and Mirrodin blocks, and finally culminated in permanently warping the very nature of all Planeswalkers Sparks both currently held and from that point forward. Because one private didn't check the body, the Multiverse was forever changed.
[[/folder]]

[[folder:Theater]]
* ZerothLawOfTropeExamples: Romeo's servant Balthasar in ''RomeoAndJuliet'', when he brings his message to Romeo telling him of Juliet's death. Sadly, the friar's letter telling him that the death was faked does not get through - so there are ''two'' Swiss Messengers, the one who delivers the wrong news, and the one who doesn't realize how important the ''real'' news is, and fails to deliver it. Actually seems to have achieved some degree of PopCulturalOsmosis, which runs counter to the norm for an author so prone to EverybodyKnowsThat.
* In Creator/OscarWilde's An Ideal Husband, the scatty Lady Markby brings a friend to a party, appearing in two scenes in the first act, and never appears onstage again. Said friend turns out to know their host's dirty secret, thus causing the events of the entire play.
* CyranoDeBergerac: Hilarously subverted by De Guiche: he is a villain who unwittingly derails his own plans: At Act I Scene IV, he utters a simple DareToBeBadass to De Valvert, a small but crucial gesture that [[DisasterDominoes sets events that result in]] the derailment of his own plan to [[ArrangedMarriage marry]] Roxane with [[TheBeard De Valvert]] so de Guiche could bully her to be his [[TheMistress mistress]].
* Theatre/{{Sweeney Todd|TheDemonBarberOfFleetStreet}} would never have gone on his murder spree as the Demon Barber of Fleet Street had Anthony not barged into his shop, with Judge Turpin ''right there in the damned room'', in order to inform Sweeney of his plans to elope with Johanna, bombing both plans to hell and making everything worse.
* ''Theatre/{{Brand}} has Gerd, a CloudCuckoolander who crosses paths with the main character time and again, prompting his choices to the worse. At the end of the play, she is the one who fires the shot to loosen the lavine that buries the entire community completely (and everybody in it). Justified because she is obsessed by the thought of getting a shot on "the bad priest on the black peak". Whatever that is.
* ''Theatre/IntoTheWoods'': After all the fairytale events, one of the consequences is that the widow of the giant Jack killed comes down seeking revenge against Jack. However, it's during the song "Your Fault" that the other characters learn that they were all indirectly responsible - the Baker was the one who gave Jack the magic beans in exchange for Milky-White, his wife attempted to give Cinderella an extra bean in exchange for her golden slipper, which she promptly threw away (it was this second beanstalk that the giant's widow climbed down), Red Riding Hood dared Jack to get the harp, which was the point where the giant became aware of Jack stealing their stuff, and the Witch was the one who raised the beans in the first place.
* As Captain Henry Wirz testifies during the climax of ''Theatre/TheAndersonvilleTrial'', General Sherman's march through and destruction of Atlanta only exacerbated the problems at Andersonville.
[[/folder]]

[[folder:Toys]]
* Literally everything that happened in ''{{BIONICLE}}'' can be traced back to two characters' actions: Annona, who amplified the Great Beings' pre-existing compulsion to create, which eventually led to the Great Spirit Robot; and the Energized Protodermis Entity, who let the Core War happen and caused Spherus Magna to shatter. While it's debatable exactly how much of this was "unwitting", it's doubtful either of them foresaw just how much of an impact their actions would have.
[[/folder]]

[[folder:Video Games]]
* In ''VideoGame/{{Bastion}}'' [[spoiler:The ManipulativeBastard who seduced and betrayed Zia]] indirectly caused [[ApocalypseHow The Calamity]] by [[spoiler:driving Zia's father into sabotaging the Calamity and getting the Mancers panicked enough to set it off.]]
* In ''VideoGame/DragonQuestIX'', during a pre-game flashback, [[spoiler:Serena's father is responsible for Corvus' StartOfDarkness by showing up at the worst possible moment lying to the guards that Serena tricked Corvus into drinking a sleeping potion in order to have him sold out to the Gittingham Empire in exchange for their village's safety. Corvus feels that he has been betrayed, and in spite of fulfilling his end of the bargain, Serena's father, [[YouSaidYouWouldLetThemGo and Serena herself, who he was trying to protect]], [[ILied are both still murdered by the soldiers for their trouble]], and Corvus is locked up for 300 years]]. When he is finally freed near the end of the game, [[WoobieDestroyerOfWorlds he intends to destroy humanity in light of the perceived betrayal he suffered]] which has led him to believe that HumansAreBastards. [[NiceJobBreakingItHero Thanks for nothing, old man]]]].
* ''VideoGame/FinalFantasyX'': So Yuna and her friends have uncovered the truth about [[spoiler:Maester Seymour]], and are getting ready to [[spoiler:send his ass to the Farplane]], when [[spoiler:Trommel]] intervenes and interrupts the ritual. Then, [[spoiler:Trommel, after being confronted with Seymour's wrongdoing ''destroys the sphere of Seymour's father warning about his son's StartOfDarkness'', with the excuse that "the Guado deal with Guado affairs."]] Needless to say, with this action, [[spoiler:Yuna and company are forced into hostile terms with not just the Guado, but ''the entirety of Spira as well'', and the unsent Seymour goes on to attack the party several times, proving to be a deadly recurring villain. The decision does later cause trouble for the Guado when Seymour nearly wipes out the Ronso, leading to the near retaliatory genocide of the Guado in the sequel.]]
* ''VideoGame/MassEffect2'' has a slight case of this in [[DisabledSnarker Joker]]. Shepard ''{{di|sneyDeath}}es'' at the start of the game specifically because Joker refused to leave the Normandy when it was going down in flames. Shepard was forced to pull off a Heroic Sacrifice for him. Despite this, Joker is still a popular character, but it did earn him some haters. (Then again, if Shepard hadn't died in the beginning, Cerberus wouldn't have given Shepard the ''Normandy'' SR-2 and a whole new BadassCrew, and it's unlikely that the Alliance would have been so generous...)
** It stops being an elephant in the room in ''VideoGame/MassEffect3''. In the Paragon post-Thessia conversation, Joker admits that he blames himself for Shepard dying and now being "like, half-robot at this point - no offense, EDI." It also has some surprising long-range consequences for the ending that no one could have anticipated at the time; [[spoiler:because Shepard is a mixture of an organic and a synthetic, s/he can now select the "Synthesis" option, breaking down the barriers between synthetics and organics, but on the down side, "Destroy" will almost certainly kill Shepard along with other synthetics unless the player has enough Effective Military Strength]].
* In the "Invasion of the Firelands" quest chain in ''VideoGame/WorldOfWarcraft'', the players can become one in a rare instance in which they cause disaster without being an UnwittingPawn. Shortly before the attack on the Firelands is about to begin, Hamuul asks the player to investigate a Druid of the Flame nearby. The Druid of the Flame, Leyara, attacks the player and Hamuul, badly burning Hamuul and preventing the protectors of Hyjal from going on the offensive until the player gets enough Marks of the World Tree to unlock the next phase of daily quests.
** There were many people, events and circumstances that caused Garrosh Hellscream to become the BigBad of Mists of Pandaria. But who ultimately introduced him to Thrall, causing him to bring Garrosh out of his HeroicBSOD and make him his successor as Warchief? The Horde players did, while questing in Nagrand, two expansions before Garrosh's rise to power.
** In ''Wrath of the Lich King'', the Horde is betrayed by the Royal Apothecary Society of Undercity, under the command of Varimathras and Apothecary Putress. Who did the legwork for most of their twisted experiments with the New Plague? Three guesses, first two don't count. [[spoiler:Horde players doing all those Apothecary quests all the way back to Vanilla.]]
** Garrosh Hellscream's escape to alternate Draenor is done with the help of a bronze dragon, Kairoz. How does Kairoz manage to open a portal to another dimension despite the bronze dragon's losing their powers at the end of Cataclysm? By collecting Epoch Stones from the Timeless Isle to create the Vision of Time, a device that can traverse timelines. And who helps collect those stones? Oh that's right, ''the player''. [[spoiler: This could have even bigger ramifications than previously thought- as well as Garrosh's Iron Horde invasion, Warlords of Draenor seems t be building up to a ''Burning Legion'' invasion of our Azeroth.]]
* In ''VideoGame/FinalFantasyII'', the party needs to get inside Kashuon Castle, but with Gordon, the only surviving member of the royal family, unavailable, they must go to look for an item that lets them gain entry. During the mission, [[spoiler:Josef]] is killed, and Gordon gets a WhatTheHellHero from Hilde, who blames him for [[spoiler:Josef]]'s death.
* In ''VideoGame/TheElderScrollsVSkyrim'', Aventus Aretino is a boy who wants to summon [[MurderInc the Dark Brotherhood]] to kill the evil headmistress of an orphanage in Riften. Being the PlayerCharacter, you, naturally, have to do the deed. By doing so, you actually come into contact with the Brotherhood, who want to recruit you. [[spoiler:You can either turn on their leader, silencing what is possibly one of the last branches of the Brotherhood, or you can join them, starting a blood-soaked questline that culminates in you personally killing the Emperor. All because of this little boy's wish.]]
* In ''VideoGame/MetroidPrime'', [[spoiler:the Omega Pirate tried to crush Samus upon death, giving her the Phazon Suit. At first the suit proved useful for the protagonist, even helping her to defeat the eponymous FinalBoss by using the Hypermode ability for the first time. But after the battle, the renmants of the DNA of Samus (and, by extension, that of the Omega Pirate) in the Phazon Suit led to the creation of ''Dark Samus''.]]
* [[spoiler:[[[VideoGame/GrandTheftAutoIvTheLostAndDamned Ashley Butler]]]] in a cameo in ''VideoGame/GrandTheftAutoV'', [[spoiler:has sex with the violently unstable Trevor Phillips for a quick fix. This leads to the death of Johnny Klebitz, the massacre of the entire Liberty City chapter of The Lost, and Ashley herself either being killed by Trevor, or dying in a crack orgy afterwards.]]
* [[spoiler:Cole Phelps]] of ''LANoire'' is a pretty big one. [[spoiler:A good chunk of the horrible things that happen throughout the game are ultimately a result of his glory-hounding and incompetence during the war. Not only was he directly responsible for driving Hogeboom insane and hardening Courtney Sheldon's heart and indirectly for Kelso's code of silence about their respective misdeeds during and after the war, but the military surplus heist was entirely driven by his former comrades' resentment of Cole for his undeserved honors]]. When [[spoiler:Cole]] realizes what he's responsible for he's ultimately DrivenToSuicide.
* In VideoGame/MegaManX, an archaeologist, Doctor Cain digs up a hundred-year-old genuinely heroic and kind fully sapient robot, X, who is more advanced than anything known to modern science, to the point that parts can't even be understood. Nevertheless, he tries duplicating the robot, and many other people follow suit, since the resulting replica androids are useful for all sorts of tasks and more intelligent than anything previous. This ultimately leads to at least a half-dozen apocalypses and, ultimately, the extinction of the human species. After waking X up and popularizing replica androids, Cain more or less never appears again. It is hinted that he died of old age only shortly before everything starts going to hell with the first ColonyDrop.
* In "The Trouble with Clones" DLC of ''VideoGame/SaintsRowTheThird'' [[spoiler:the Aisha and Tag Brutes have gotten together and it looks like you'll be able to take them away without further trouble... then a National Guard helicopter blows the Aisha Brute up with a missile and the Tag Brute runs away again.]]
* [[spoiler:Boah]] from FireEmblemAkaneia is this, for [[spoiler:convincing Princess Nyna to marry Prince Hardin, a man whom she cares for but is not ''in'' romantic love with ([[LoveTriangle she loves Camus the Black Knight while Hardin is in love with her]]), for the sake of the Archanea continent.]] The consequences? [[spoiler:Emperor Hardin finds out later and [[HeroicBSOD falls into]] [[DrowningMySorrows drunken depression]], allowing his defenses to become low enough to get BrainwashedAndCrazy when given a certain [[MacGuffin Dragonsphere]] by a disguised villain... and ultimately, to have [[FallenHero Hardin]] ''as the BigBad of the second part of the game''.]] [[spoiler:And Boah pays ''with his own life'', his FamousLastWords to Marth being an apology for the mess he caused while trying to help everyone.]]
* In the ''Videogame/{{Borderlands}}'' series, [[BigBad Handsome Jack's]] hunger for the riches of the mysterious Eridian Vaults unwittingly set into motion [[spoiler: an apocalyptic war that would kill billions of people]]. In fact, [[Videogame/BorderlandsThePreSequel Jack was warned about this repeatedly by Colonel Zarpedon and her Lost Legion]], whose mission was to either defend the Vaults or destroy them to prevent them from falling into the hands of humans, but Jack dismissed everything they said and was so blinded by his own greed that he never even considered turning back.
* ''Franchise/DragonAge'':
** Varric Tethras once found out about a family of destitute former nobles trying to earn enough coin to buy back their estate. Taking a liking to them and figuring they could help, he decided to let them in on an expedition to the Deep Roads. Through an unlikely chain of events, this eventually leads to a civil war and nearly the ''apocalypse''.
** The Warden Commander of Ferelden (regardless of whether s/he was the Hero who vanquished the Blight or an Orlesian Warden sent as replacement) took the runaway mage Anders under his/her wing, protected him from the Templars who had been pursuing him, thus showing him that Templars could be openly defied and led him to meet the spirit of Justice, events which started Anders' radicalization and led to the eventual start of the Mage-Templar war.
** Hawke, and not just because s/he started the Mage-Templar War. In fact, the entire reason the Breach opened and the world is being threatened in ''Inquisition'' is because [[spoiler:Hawke accidentally released Corypheus from his prison while trying to stop a cult from doing the same in the ''Legacy'' DLC.]]
** It is revealed in ''VideoGame/DragonAgeInquisition'' that the capacity for the Rite of Tranquility to strip mages of their magic [[spoiler:was discovered when a mage attempted to join the Seekers of Truth. Without that, the Seekers would never have started using the Rite on mages, and its use would not have been abused for political, and occasionally [[PrisonRape baser]], purposes, which are among the things that led mages to rebel. All because of one well-meaning mage who thought he found a reliable way to keep mages from becoming [[DemonicPossession possessed]].]]
* The (largely) unseen child killer in the ''Videogame/FiveNightsAtFreddys'' series seems to have no idea that his murders have been the cause of every bad thing seen throughout, as [[spoiler:his victims haunt the animatronics, leading to the death of at least one security guard, the Bite of '87, the closing of Freddy Fazbear's Pizza and, ironically enough, his own death (and subsequent possession of Springtrap)]].
[[/folder]]

[[folder:Visual Novels]]
* ''VisualNovel/SchoolDays'':
** Sekai seduces Makoto because of her own unrequited feelings for him, [[MatchmakerCrush despite actually hooking him up with another girl, Kotonoha.]] This action itself, in the anime continuity, is what leads to Makoto developing a sex addiction, cheating on Sekai with Otome, and then Otome with every other girl in his class, Kotonoha becoming a {{Yandere}}, and well [[DownerEnding the nice boat.]]
** [[spoiler:Otome and Makoto]] might be even worse ones in some routes. It's depending on Makoto pulling one or another action that [[spoiler:Otome will or not tell Makoto's best friend Taisuke that girls like forceful dudes during sex -- which will lead him to rape his crush Kotonoha, under the very stupid belief that the poor girl's barely whispered "no, don't..." are actually a part of the "protest pretend" kink. [[note]]where the passive partner in hentai/ecchi/hard yaoi/etc. media fakes being embarrassment and unwillingness.[[/note]].]]
** Also, [[spoiler: Nanami, Hikari and Otome's GirlPosse]] can become the trope, when [[spoiler: they '''horribly''' bully Kotonoha to [[ShippingTorpedo keep her away from Makoto]] [[ShipperOnDeck and make sure Sekai gets him]].]] This can either lead to [[spoiler: Makoto ''completely cutting Sekai off his life'' before choosing Kotonoha since he thinks she's the one instigating the bullying that Koto has been a victim of [[note]](she's almost surely '''not''', but Makoto is simply too angry to consider that because school bullying is his BerserkButton)[[/note]] ]] or to [[spoiler: Kotonoha [[GoMadFromtheRevelation breaking down so badly]] for said harrassment that ''she murders Sekai in broad daylight''.]] In either way, their support to one girl over the other ''makes things MUCH worse for the one they wanted to "help"''.
* ''VisualNovel/UminekoWhenTheyCry'':
** [[spoiler:Battler Ushiromiya]] of all people, who drives [[spoiler:Sayo Yasuda]] to orchestrate the murders [[spoiler:by unwittingly breaking a promise to take them away from Rokkenjima]]. Mind you, Battler didn't come back for it because of family issues, but unfortunately, [[spoiler:the already mentally broken Sayo]] took this very, ''very'' badly.
** Furthermore, if that's the case, then [[spoiler: ''Rudolf and Kyrie'']] are also responsible. [[spoiler: Had they not [[ParentWithNewParamour married too soon after the death of Battler's beloved mother]] for Battler's taste, he would have not broken ties with his paternal family, therefore he would've returned to Rokkenjima sooner and/or more frequently and would've likely found a way to help Sayo deal with their crappy situation, promise or not.]]
** There's also [[spoiler:Natsuhi]], who is largely responsible for [[spoiler:Sayo Yasuda]]'s issues in the first place. [[spoiler:Sayo, who would have been known as Lion Ushiromiya, was given to her by Kinzo as a baby to raise after she couldn't give birth to an heir. One day, out of anger and resentment out of having to raise a child that wasn't her own, she pushed a servant holding the baby off a cliff. The servant died, but the baby survived, though with injuries that damaged their sexual organs, leading to Sayo having major gender/body issues later in life.]]
* There are two of them in ''VisualNovel/HigurashiWhenTheyCry'':
** Ooishi, whose InspectorJavert tendencies provoke the events of the Spirited Away and Atonement chapters.
** Oryou, whose actions and policies are directly responsible for Cotton Drifting and Eye Opening or indirectly responsible for many of the other chapters via the treatment of the Hojo siblings and in provoking Ooishi above.
* ''Franchise/AceAttorney'':
** The games have one (although it's more attributed to the series being a LongRunner more than anything): [[spoiler:Tsukasa Oyashiki]] is indirectly responsible for the DL-6 incident, thanks to [[spoiler:inadvertently hiding the IS-7 victim's body. This was due to the fact that she was trying to prevent the destruction of some ice statues made by the victim, and didn't even know the killer hid the body there. Because of that, she's responsible for the forgery of evidence and Manfred von Karma's black spot on his perfect record]]. Even worse, the DL-6 Incident led to [[spoiler:the Feys losing their reputation, causing Morgan's husband to leave her and Dahlia to grow up to become a serial killer.]] Poor [[spoiler:Tsukasa]]'s got a ''lot'' of blood on [[spoiler:her]] hands.
** Jake Marshall is one for Case 1-5. He approaches Bruce Goodman, asking him to re-open SL-9, but Goodman refuses. Marshall then steals Goodman's ID to retrieve the evidence himself, prompting Goodman to have to enter the evidence room with [[spoiler:Police Chief Damon Gant]] in order to complete the transferal. Not realizing he was with Neil Marshall's true killer, Goodman changes his mind and suggests reopening the case, [[spoiler:and is killed on the spot before being transported to the underground parking lot]]. Marshall thus, either by stealing Goodman's ID or planting a seed of doubt in Goodman, indirectly caused Goodman's death.
* During Hanako's route in the VisualNovel ''KatawaShoujo'' [[spoiler:Misha]] decides to teasingly question her and Hisao about their relationship. As a result of this queston [[spoiler:Hisao is forced into a situation where he had to tell Hanako about the suprise birthday party that he and Lily were planning for her. This just happens to cause [[FragileFlower Hanako]] to have [[AngstComa a SEVERE panic attack]].]] In [[spoiler:Misha]]'s defense she truly didn't know that [[spoiler:[[BirthdayHater Hanako's birthday]] was a {{trigger}} for her]], and she's genuinely sorry for the consequences.
* Ryousuke Katayama of ''VisualNovel/CorpseParty'' is a weird example, in that it's not exactly his fault. [[spoiler:In Tenjin Elementary School, he loses his leg in a trap and bleeds to death.]] His friend Ohkawa, however, [[spoiler:insists that he's still alive and needs to get to a hospital. In an attempt to "help" him realize the truth, Kizami pushes his body down the stairs]]. [[FreakOut This works about as well as you'd expect]]. Ohkawa [[spoiler:calls Kizami a murderer, which causes Kizami to have an "epiphany": It doesn't matter whether it's the school that kills you or him]].
[[/folder]]

[[folder:Web Comics]]
* In ''Webcomic/KidRadd'', two Moderators are given a large sum of money in order to hire an assassin to kill Radd, as Captain QB can't be directly implicated in illegal activities and needs to use a proxy. They reason that it can't be hard to kill someone in jail (as Radd is being imprisoned for illegally entering other games), and hire Kobayashi the discount ninja so that they can pocket the rest of the money. Radd survives the assassination attempt and Kobayashi becomes a recurring character who later meets up with Gnarl and, while training together, stumbles upon [[spoiler:Chimera Point, the keystone to Crystal's plans, which eventually results in ''her'' finding it too]].
* In the ComicBook/ChickTract "Fatal Decision", Brutus, an orderly on the brink of being fired for rudeness to patients, makes hints that John shouldn't trust Dr. Bowers, leading to John destroying the vaccine and dying of his disease.
** The devils often invoke this trope, choosing someone who has an incidental relationship to the person whose soul they want to claim. In "The Assignment" they succeed in convincing Charles Bishop's subordinate's wife to badger him out of witnessing to his boss. They try to distract Cathy with a boy, only for it to fail when he proves to be a JerkAss, and try to have the previously mentioned subordinate call Bishop with a sales proposition, only for the angels to thwart this attempt twice. Charles ultimately dies in his sins, making the first example a successful one.
* In ''Webcomic/KevinAndKell'', [[Webcomic/GeneralProtectionFault Nick and Ki's]] [[{{Crossover}} arrival in Domain]] by way of interdimensional travel disrupts the balance between the animal- and human-dominated worlds to the point at which the other two humans living on the animal side [[spoiler:Lindesfarne and Danielle]] are forced to leave lest the world suffer instinct loss. [[spoiler:Luckily, Catherine and Nigel do it instead]].
* [[KnightTemplar Miko Miyazaki]] from ''Webcomic/TheOrderOfTheStick'', having already [[DePower lost her Paladin abilities]] through the unwarranted execution of of Lord Shojo, ends up destroying the [[MacGuffin Sapphire Gate]], having once again misinterpreted what the gods wanted of her. Had she not been so hasty in doing this, the ghost of [[PrecursorHeroes Soon Kim]] could have permanently ended the threat of [[BigBad Xykon]] and [[DragonWithAnAgenda Redcloak]], who, themselves, were aiming for the gate, anyway.
* Several characters in ''Webcomic/{{minus}}'' take actions that, unbeknownst to them, lead to TheEndOfTheWorldAsWeKnowIt. First, a mysterious man pretty much "breaks" [[RealityWarper minus]] by stuffing her into a briefcase. She is freed, but becomes a CloudCuckooLander. In an attempt to cure her, the green-haired girl throws a rock at minus's head, causing her [[spoiler:[[LiterallyShatteredLives to shatter]]]]. Because she is now [[spoiler:a ghost]], minus starts to spend more time with her ghost friends than her live ones. Which leads to the biggest example of this trope in the comic: the red-haired ghost asks minus to bring her back to life, because she has some UnfinishedBusiness with certain humans that the readers don't get to see. minus agrees. Unfortunately, once the other ghosts find out, they demand that minus revive them too. She does, [[spoiler:only for the sheer influx of bodies on Earth to suffocate every living thing on the planet, including those who were just revived]]. [[SpaceWhaleAesop And that is why you should never ask anything of an omnipotent being, ever.]]
* Virtually everyone in ''Webcomic/{{Homestuck}}''; the ''single'' good character who doesn't manage this is Nepeta[[note]]largely because she's never shown actually ''doing'' much of anything; the one time she tries to do something significant she's hopelessly outclassed and dies pointlessly and almost immediately[[/note]].
** Tavros deserves special mention. At one point he attempts to save a young Jade from accidentally shooting herself by taking psychic control of her dog, Bequerel, and deflecting the shot at her grandfather (whom he believed was a hostile intruder), killing him. He then points out that Bequerel would have saved her even if he hadn't done anything (in a way that would not have killed Grandpa Harley) and that he only interfered so he could feel a little better about himself. Even when she points out that killing her grandfather was ''not'' appreciated, he still thinks he made the right choice.
* In ''Webcomic/{{Freefall}}'', Florence has suspicions that Maxwell Post might be this when she learns that he is the spiritual advisor to the [[AIIsACrapshoot sapient robot]] population. [[SubvertedTrope So far, his efforts have been among the least of her worries.]]
* One ''Webcomic/ElGoonishShive'' storyline featured a rampaging boar which was enchanted to grow to an enormous size. Said enchantment is heavily implied to have come from [[spoiler:Rhoda]], who was unwittingly given a [[PowerTattoo magic mark]] and unknowingly used it on the boar while in a state of panic.
[[/folder]]

[[folder:Web Original]]
* In ''Machinima/RedVsBlue'', it's revealed in season 10 that [[spoiler:Carolina]]'s pride was responsible for nearly everything bad that happened to the Freelancers--[[spoiler:her original AI was Sigma, but she gave him up to Maine. Sigma and Maine went on to become the Meta and kill several other Freelancers. When she finally did get an AI, she took ''two'': the ones that were originally meant for Wash and South. South's jealousy due to her brother North getting an AI and her not led to South leaving North to die and shooting Wash in the back, and her own death at Wash's hands later. Wash, on the other hand, did get an AI... Epsilon. Which led to him going insane and plotting to take down the Director of Project Freelancer for his crimes.]] All because of pride.
** Even before that there [[spoiler:was the Director's obsession with his dead love, Allison. When the Alpha AI, copied from the Director's mind, was created, the Beta AI (based on the Director's memories of Allison) naturally fragmented from it. This inspired the Director to torture the Alpha into making more fragments, the ones mentioned above, to figure out a way to "get her right".]]
** There was also [[spoiler:the Sleeveless Insurrectionist Soldier, who shot Agent Maine in the throat several times, rendering him mute. This gave Carolina an excuse to give her A.I. Sigma away so that Maine could have an alternate way to speak. This contributed into forever turning him into the Meta.]]
* Trouble in ''Roleplay/DinoAttackRPG'', being a mutant lizard who was adopted and trained by a member of the team trying to eradicate his kind, was the first to spark the tension between realist and idealist members of the team. Technically speaking he is responsible both for the campaigns by both Kotua ''and'' Cam O'Cozy, both of whom tried to commit genocide against idealist agents.
* In ''WebAnimation/DeathBattle'', [[WesternAnimation/HeManAndTheMastersOfTheUniverse1983 He-Man]] ended up as this during his fight against [[WesternAnimation/ThunderCats Lion-O]]. He just wanted to fend off Lion-O, but in doing so, [[spoiler:he crushed the Eye of Thundera, which kept the Thunderan race alive.]]
* In ''WebOriginal/{{Worm}}'', the Undersider's local [[TheSmartGuy Smart Girl]], Tattletale, normally isn't this, but a character flaw of hers is to start throwing everything her SherlockScan superpower picks up everywhere when she panics. This doesn't really hurt anyone...with the rather glaring exception of [[spoiler:cluing [[TheMedic Panacea]] into her family history...which sets off the [[DysfunctionJunction time bomb]] of issues that is her adopted family, and ends with Panacea's incarceration and her sister becoming a [[AndIMustScream miserable pile of immobile flesh]].]]
[[/folder]]

[[folder:Western Animation]]
* A strange example of a fictional character ending up being one for the real-life events. ''TheRenAndStimpyShow'' had the minor character George Liquor getting brutally beaten up by Ren in the episode "Man's Best Friend". Said scene was later one of the reasons for creator Creator/JohnKricfalusi's firing.
* ''WesternAnimation/AvatarTheLastAirbender'': The Earth King informed Azula (disguised as a Kyoshi Warrior) of the invasion of the Fire Nation. Cue next season where the invasion force finds all royalty in hiding, and the invasion ends in failure with almost all of them captured.
* ''WesternAnimation/AdventureTime'':
** The Ice King continually interferes with Finn's attempt to prevent [[VileVillainSaccharineShow the Lich]] from reaching the Well of Power and regaining his full power. As a result the Lich, having regained his full power by the time Finn and Jake finally reach him, [[NoHoldsBarredBeatdown ends up jobbing Finn]] and destroying the Gauntlet, the one weapon that can hurt him, forcing Finn to find an alternative. Then the Ice King accidentally drops Bubblegum into the Well, which melts her and allows the Lich to possess her. After being frozen with help from the Ice King, she shatters, requiring medical attention to be put back together. Part of Bubblegum is missing though, causing her to come back as a 13-year old, which later results in [[RoyalBrat Earl of Lemongrab]] assuming the throne, if only for an episode.
*** The snail was responsible for the Lich breaking free in the first place. He just happened to have crawled into Finn's backpack right before Princess Bubblegum took Finn and Jake to the location of [[CrystalPrison the Lich's imprisonment]]. As soon as he crawled out, the snail, having no psychic protection, was mind controlled by the Lich into freeing him and setting the above chain of events into place, not to mention the ongoing threat of the Lich when [[spoiler:the Lich possesses the snail directly]].
** If it weren't for an unnamed Scandinavian dock worker selling an old crown to an antiquarian [[spoiler:by the name of Simon Petrikov]], the Ice King would never have existed. However, if that happened then [[spoiler:Marceline]] would have most likely died in the [[AfterTheEnd post-apocalyptic wasteland]], so it isn't all bad.
** In the AlternateUniverse [[FanNickname "Farmworld"]], the Destiny Gang terrorising Finn's village and his family leads to ''him'' wearing the Ice King's crown, which in turn leads to the release of the Lich and the world being inflicted with ''another'' apocalypse.
* In the one episode of ''ComboNinos'' where [[NotMeThisTime neither Diadoro nor Gomez]] had released any Divinos, Principal Bronka accidentally released a Family of snake-like Divinos.
* In the ''WesternAnimation/FostersHomeForImaginaryFriends'' special WesternAnimation/DestinationImagination, Herriman {{inter|ruptedCooldownHug}}feres with a resolution between the Face and the rest of the main characters, Frankie included, by scolding him, causing him to go berserk. Unlike most other examples of this trope, he immediately comes to regret this.
* Everything that went wrong in the ''WesternAnimation/{{Kissyfur}}'' episode "The Birds And The Bears", from the cubs taking Gus' paddlecab for a spin which eventually leads them through dangerous rapids to the gators taking control of the paddlecab and using it to capture the cubs, all happened thanks to [[OneEpisodeWonder Donna's]] rebellious behavior. She even [[LaserGuidedKarma gets called out for it]] when she and some of the other cubs are captured by the gators.
--> '''[[JerkAss Lenny]]:''' [[JerkassHasAPoint It was]] ''[[JerkassHasAPoint your]]'' [[JerkassHasAPoint dumb idea to fool with the paddlecab, Donna!]]\\
'''Duane:''' Yeah, it definitely wasn't a cool thing to do!\\
'''[[TheEeyore Stuckey]]:''' Not cool at all!
* Homer from ''WesternAnimation/TheSimpsons'' does this at least once or twice a season. He's even responsible for the death of Maude Flanders; Homer tells a group of bimbos to aim their [[ItMakesSenseInContext 'Free t-shirt' bazookas]] at him, only to duck at the last possible second as he grabs something off the ground. The barrage of t-shirts knocks Maude over the edge of the stadium to her death in front of her ''husband and two young children''.
-->'''Homer:''' I'm the one whose antics drove her out of her seat. I'm the one who provoked the lethal barrage of t-shirts. [[RuleOfThree I'm the one]] who parked in the ambulance zone, preventing any possible resuscitation.
[[/folder]]

[[folder:Real Life]]
* Creator/SamuelTaylorColeridge had a vivid dream, got up and started writing it down as the epic poem ''Kubla Khan'', [[http://sydneypadua.com/2dgoggles/the-person-from-porlock/ but then there was a knock at the door,]] and a man from the nearby town of Porlock kept him talking just long enough to forget all about the dream and he never finished it. The [[http://en.wikipedia.org/wiki/Person_from_Porlock Person from Porlock]] is now literary shorthand for an unwanted visitor.
** Though some have theorized that Coleridge never intended to finish the poem (or that it was finished already), and he made up the story of the visitor just to mess with people. It doesn't help that Coleridge was a heavy opiate user, and the "dream" could have been something more of a "drug-induced vision," and the man from Porlock may or may not have actually been there. (Cue images of a poet standing on his doorstep talking to nobody while hazy visions of Kublai Khan's utopia dissipate into the aether.)
* Andy Dick. At a 1997 Christmas party, he reintroduced Brynn Omdahl, wife of Creator/PhilHartman, to cocaine, leading to his death. Which led to Andy Dick [[KickTheDog making some tasteless jokes about his role in Hartman's death,]] which resulted in Hartman's friend Jon Lovitz kicking his ass. It appears that Dick lives up to his name.
* Floyd Wells. He told fellow cons Perry Smith and Richard Hickock that a farmer he worked for named Herb Clutter kept a safe hidden with plenty of cash inside. As it turned out, there was no safe. It was this false info that led Smith and Hickock to massacre Mr. Clutter and his family, the basis for Creator/TrumanCapote's ''Literature/InColdBlood''.
* A rare inversion in [[http://en.wikipedia.org/wiki/Stanislav_Petrov Stanislav Petrov]]. While monitoring a satellite for the Soviet early warning system of a nuclear attack, he received a report of five inbound [=ICBMs=]. He decided it didn't make sense for a US first strike to be composed of only five nukes, and logged it as a technical error. Had he not been so cautious, WorldWarIII surely would have erupted.
* The failure of the Jay Leno Show on primetime had this effect on Creator/ConanOBrien's tenure as host of TheTonightShow, as it damaged local 11pm newscast ratings, as well as Conan himself, leading NBC to move Jay and his show back to his old 11:35 spot, and pushing Conan just past midnight. Conan, [[JudgmentOfSolomon not wanting to tarnish the legacy of the Tonight Show]], wanted no part of the agreement, and was subsequently evicted from the show, with Jay back as host.
* Senator Stephen Douglas, the man responsible for the Kansas-Nebraska Act. Originally, his intentions had simply been to get a railroad to California built, which would start in Chicago, Illinois (his home state). To do this, he proposed splitting the remaining unorganized chunk of the Louisiana Territory into the territories of Kansas and Nebraska. Pro-slavery Southerners slipped in a part saying that the legality of slavery in each territory would be decided by the voters there. But then pro-slavery advocates from Missouri flooded into Kansas to support slavery, resulting in "Bloody Kansas", the prequel to UsefulNotes/TheAmericanCivilWar. Douglas himself has been branded pro-slavery for years afterward following the fallout, with historians often leaving out that it was the South that suggested the decision of slavery by popular sovereignty and that Douglas himself wanted to build a railroad to California, obviously having no idea that the first planned transcontinental railroad would cause [[UsefulNotes/TheAmericanCivilWar the biggest schism ever to hit the United States]] over completely unrelated circumstances.
* In 2007, Creator/AdultSwim launched a guerrilla marketing campaign for the ''WesternAnimation/AquaTeenHungerForce'' [[TheMovie movie]] featuring battery-powered LED placards resembling the Mooninite characters being placed in numerous places around the US. However in Boston, police officials mistakenly thought that the [=LEDs=] were bombs, and treated the whole event as such. This event would turn out to known as the [[http://en.wikipedia.org/wiki/2007_Boston_bomb_scare Boston Bomb Scare]], which lead to legal implications being placed on Turner Broadcasting and their contractors, the internet to make mock [[MemeticMutation "Never Forget" memes]], and forced then-current Creator/CartoonNetwork head Jim Samples to step down. It wouldn’t be long after until fans began to realize that Creator/CartoonNetwork would not be the same since the incident. Not because of any legal incidents, but because Sample’s replacement, Stuart Snyder, became the instigator of the channel’s infamous NetworkDecay in the late-2000s, with an increase of live-action sitcoms and reality shows on the channel.
* Franz von Papen, ex-Chancellor of the Weimar Republic, who in 1933 convinced President Hindenburg to make UsefulNotes/AdolfHitler chancellor in order to save his own political hide. By this point, the Nazis (forced by previous chancellors to fight repeated elections which sapped their funds) were rapidly losing support and were scraping the bottom of their piggy bank.
** And in an even worse example, Marinus van der Lubbe, the guy who started the Reichstag fire. He was a raving madman who was quickly captured that same night. It gave the Nazis the perfect opportunity to seize power, as the aforementioned repeated elections would eventually end in a loss of NSDAP seats.
* In the mid-'80s bribery scandal linked to R. Budd Dwyer (the inspiration behind "Hey Man, Nice Shot" by Music/{{Filter}}), William Smith, an attorney linked to the case, gave dubious testimony in order to accept a plea bargain, which made a guilty verdict for the former practically inevitable. As a result, Dwyer himself [[AteHisGun publicly committed suicide]] the day before the sentencing was to have taken place.
* In the night of April 14, 1912 Jack Phillips, radio operator of the ''RMS Titanic'', received a message alerting of an ice field ahead from the radio operator of the ''SS Californian'', Cyril Evans. The message interrupted an information directed to a first class passenger from Cape Race, Newfoundland, and Phillips radioed "Shut up, shut up! I am busy; I am working Cape Race!" back to Evans. Annoyed, Evans turned off the radio and went to sleep... ten minutes before the ''Titanic'' struck an iceberg. This prevented the ''Californian'' (who was the closest ship to the ''Titanic'') from hearing the ''Titanic'''s repeated distress calls and rescuing her passage before the ship went down.
** David Blair was originally slated to be Second Officer of the ''Titanic'' during her maiden voyage. However, in the last moment White Star reassigned the more experienced Henry Wilde, Chief Officer of the ''Olympic'' (at the time in drydock) to the ''Titanic'', and the knock-off effect was Blair being given another post out of the ship. By accident, Blair left with a key from the ''Titanic'', that turned out to be the only key to a safe in the Crow's Nest keeping the lookouts' binoculars. Without binoculars, the lookouts failed to see the iceberg in time.
* Jamie Gorelick, during her tenure as Deputy US Attorney General, was responsible for strengthening the restrictions on information sharing between domestic and foreign intelligence services. [[RightHandVersusLeftHand The lack of coordination]] this caused lead directly to the US government's failure to prevent the September 11th attacks, despite ample evidence of the plot, up to and including one of the terrorists being (briefly) taken into custody not long before it happened.
* Creator/SethRogen has become this with regards to the now-notorious consequences from ''Film/TheInterview'' and the cost it left Sony with. He knew that the film would piss off North Korea, and went ahead with it, presumably figuring that the DPRK would once again fail to follow up on its threats. However, he probably couldn't have seen his move as coming at the cost of the financial stability of the company he was working for, or The Guardians of Peace outright threatening terrorist attacks in theatres where it was due to play.
* On April 20, 2007, Davon Boddie was arrested for pot dealing outside of the Royal Suite nightclub in Roanoke, Virginia. Boddie was the cousin of [[UsefulNotes/AmericanFootball Atlanta Falcons quarterback]] Michael Vick, and gave Vick's home address as his own. Five days later, police searched the home and discovered a massive [[http://en.wikipedia.org/wiki/Bad_Newz_Kennels_dog_fighting_investigation dog-fighting ring]], leading to the arrest and conviction of Vick and four others.
* Gavrilo Princip and his co-conspirators in the assassination of Archduke Franz Ferdinand. All they wanted was a re-arrangement of some political borders in one part of the Balkans. What they got was a world-spanning war which was the deadliest in history, which led to the fall of the European colonial powers and the rise of communism, ''another'' world-spanning war 20 years later which became the new most deadliest war in history as a result of the mess the previous one left, and a subsequent cold war due to the results of the previous war that kept the world on the brink of destruction for fifty years. [[ArsonMurderAndJaywalking Oh, and that Balkan situation never was properly sorted out.]]
* The TGWTG WebVideo/ToBoldlyFlee movie had a lot of effort and a lot of time put into it, but it was also a big TroubledProduction with many producers having bad memories of filming. As shown in the behind the scenes feature, things were apparently running smoothly until Rob Walker had the bright idea to lie about running fifteen minutes late. You can see Doug's face fall when he's told this, and according to [[WebVideo/TheNostalgiaChick Lindsay]] and [[WebVideo/ToddInTheShadows Todd]], that's when things started to break down.
* [[WesternTerrorists Dylann Storm Roof]], a white supremacist who took pictures of himself with Confederate memorabilia some time prior, shot up a church in Charleston with the hopes of dividing the nation. Not only did he [[EpicFail fail spectacularly]], he also caused collateral damage when his actions, which turned the general public (even in the South) against the Confederate flag, managed to TARFU ''Series/TheDukesOfHazzard''[='=]s reputation, if not outright FUBAR it.
[[/folder]]

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