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For Want of a Nail
aka: Butterfly Effect

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For want of a peace activist, the future was lost.
"You don't have to change much to change everything."
Mark Rosewater, Magic: The Gathering

A story in which one small change has a ripple effect, resulting in massive changes.

The trope's name derives from a proverb-turned-poem which traces its origins as far back as the 14th century (making this Older Than Print). Probably the most well-known version is the one which appeared in Benjamin Franklin's Poor Richard's Almanac:

For want of a nail, the shoe was lost;
For want of a shoe, the horse was lost;
For want of a horse, the rider was lost;
For want of a rider, the message was lost;
For want of the message, the battle was lost;
For want of a battle, the kingdom was lost,
And all for the want of a horseshoe nail.

A Deal with the Devil will often have the "nail" as a price, something of seemingly small consequence that is in fact huge. In a series of Disaster Dominoes, the first domino often falls when the "nail" that props it up suddenly goes missing. Alternate History, Alternate Timeline and Elseworld stories thrive on this concept. When applied to Time Travel stories, it is usually referred to as the "butterfly effect".

A Sub-Trope of What If?, and related to Unwitting Instigator of Doom, Small Role, Big Impact, Dice Roll Death, Set Right What Once Went Wrong and Make Wrong What Once Went Right. A Super-Trope of Close-Enough Timeline and Big First Choice (when the player decides about the nail). If the originals meet their alternates, may result in Other Me Annoys Me or Future Me Scares Me. The It's a Wonderful Plot is a Sub-Trope. See Mirror Character. Often overlaps with In Spite of a Nail, because many stories wouldn't be that interesting if everything was different. Compare It Began with a Twist of Fate and Contrived Coincidence.

Not to be confused with the For the Want of a Nail Series fanfic saga, which does employ this trope a lot.

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  • A Staples Business Depot TV commercial from the '90s directly references the trope with a different scenario.
    For want of a paperclip, a page was lost.
    For want of a page, a contract was lost.
    For want of a contract, a deal was lost.
    For want of a deal, a factory was lost.
    For want of a factory, a company was lost.
    All for the want of a paperclip.
  • Toshiba Electronics commercials depict this inside the mind of the CEO, leading him to hold back on releasing the product to make sure it has all the features it needs, regardless of the cost. For example, adding shock-proof hard drives to their PCs. He imagines an electrician dropping his laptop, picking it up and plugging it into an outlet at a relay substation, which causes a spark that knocks out the power. This leads to a person's roommate opening the refrigerator, sniffing some milk, noticing it's spoiled but drinks it anyway, immediately turns into a zombie, and unleashes the Zombie Apocalypse on the world.
  • An ad series for DirecTV starts with a customer experiencing some flaw associated with digital cable, and their reaction cascading into random scenarios like waking up in a roadside ditch, attending their own funeral in a disguise, or re-enacting scenes from Platoon with Charlie Sheen, having their dad getting punched over a can of soup, and chasing imaginary butterflies into something highly illegal.
  • Imagine a World Without Hate, an ad by the Anti-Defamation League which shows how some people, like Yitzhak Rabin and Martin Luther King, could have changed the world had they not been assassinated, to the tune of John Lennon's Imagine.
  • A Cartoon Network ident from the 90s dedicates itself to singing the praises of a Bedrock telegram boy named Shermy and wondering what the world would be like without him. The bumper then presents a scenario where Shermy was unable to deliver a telegram to Mr. Slate about a problem with the dinosaur cranes at the Bedrock Rock Quarry because Shermy never existed. This results in one of the dinosaurs dropping a rock on Fred Flintstone's foot, which results in Fred inadvertently destroying the Smurf Village while dancing around in pain, which results in a pterodactyl picking up Papa Smurf as the Smurfs run for their lives and dropping Papa Smurf onto the windshield of George Jetson's flying car, which results in the blinded George swerving into Space Ghost's ship and going down in flames onto the Mystery Machine, which results in...well, basically the Cartoon Network 'verse descending into chaotic anarchy, all because there was never a Bedrock telegram boy named Shermy to deliver an important telegram to Mr. Slate. Moral of the story?: Appreciate those secondary characters because you never know just how important they are.

  • A king calls an augur to predict his future. Watching the birds, the augur, with a somewhat disbelieving look, proceeds to tell the king that he shall eat his own son. Heavily struck by this prediction, the king kills himself to keep it from coming true. During the week-long mourning, the kingdom was invaded. Elsewhere, a pair of birds converse about how one of them was out of his place the day of the king's death.

  • My Beloved Mother: A major conflict in the second act is Sinbell, an orphan Raised by Robots, wondering if his true, biological mother is still alive, a question he asks the village's resident doctor, Carl who might have an answer. Carl was in a hurry at the time and answered "yes", inspiring Sinbell's decision to run away from home to the big city of Hodes where his biological mother might be. Had Carl answered she's dead, Sinbell would probably accept the fact and not flee from home. Carl wouldn't be lying as the prequel reveals - Sinbell's biological mother, Aya, technically did die when she uses herself to shield her son from a gas explosion before having her consciousness transferred to Milan's robot body via Brain Uploading. If Carl had given Sinbell a different answer returning at a later point to clarify things, Sinbell's probably wouldn't have made a rash decision to flee, thereby averting the story's gut-wrenching second half.

  • In the Kingston Trio's "M.T.A." addressing transit fare increases, Charlie heads for the subway with 10 cents in his pocket for the fare, unaware that the fare has increased to 15 cents, with the conductor asking him for one more nickel, and poor Charlie is fated to ride the Boston subways forever.
  • The verses to "It's All Who You Know" by the Newsboys are two scenarios of this trope.
    • In the first verse, a slip-up in an actor's facelift leads to the failure of the show that would have saved a TV network.
    • In the second verse, a dogsled racer forgets to take a cough drop and loses his voice. He and his dogs freeze to death when "the sled got snowbound."
  • Tom Waits' song "Misery Is the River of the World" from Blood Money even includes a line from the trope namer.
    For want of a bird
    The sky was lost
    For want of a nail
    A shoe was lost
    For want of a life
    A life was lost
    For want of a toy
    A child was lost
  • The video for "Has It Come To This?" by The Streets features a split-screen of two possible day-in-the-life situations of Mike Skinner.
  • "The Want of a Nail" by Todd Rundgren.
  • The whole point of Jay-Z's American Gangster is basically showing the mirror universe where Sean Carter kept on selling drugs instead of going into music.
  • Bowling for Soup's "Almost"'s verses each have chain of events that might have happened, if not for the first event in the chain only "almost" happening:
    • Verse 1: "I almost got drunk at school at 14 / and I almost made out with the Homecoming Queen / who almost went on to be Miss Texas / but lost to a slut with much bigger breastes / who almost dropped out to move to L.A. / and was almost famous for almost a day"
    • Verse 2: "I almost held up a grocery store / where I almost did five years and then seven more / 'cause I almost caught for a fight with a thug / who almost made off with a bunch of the drugs / that I almost got hooked on when you ran away / and I wish I could've had the nerve to ask you to stay"
    • Verse 3: "And I almost wrote a song about you today / but I tore it all up / and then I threw it away"
  • While the lyrics themselves have nothing to do with it, the video for Relient K's song "Who I Am Hates Who I've Been" fits here. Apparently, where on the sidewalk you step can stop someone across the street from getting hit by a car.
  • The Bee Gees "He's A Liar":
    Was it not for the man that was blocking the drive
    Was it not for the red limousine
    I'd be millions of miles from the scene of the crime

    Mythology & Religion 
  • In Norse Mythology, Freyr is doomed to lose the fight to Surtur at Ragnarok because he gave his good sword away to Skirnir.
  • Interestingly, Nyrtia, the Etruscan goddess of fate and chance, had a nail as her attribute, and was celebrated annually by driving nails into the wall of her temple.

  • In Midst, if the narrators can be trusted. If Moc Weepe hadn't bumped into the nice old lady at the post office, everything would have been fine.

  • In Big Finish Doctor Who The Mutant Phase the Doctor and Nyssa arriving draws a Dalek over. This Dalek getting stung by a genetically-modified wasp nearly destroys the Universe. It is revealed to be a Stable Time Loop caused by Daleks from an alternate timeline, whose attempt to draw the TARDIS into the future caused it to land and create the alternate timeline, though the time loop was further made by the Dalek Emperor travelling back to prevent this.

  • In Dawn of a New Age: Oldport Blues, Finn experiences a vision of the future that points to a specific date where everything went wrong and the superheroes became known to the government. The agent recounting the details of it states that, if even a tiny thing had gone differently on that date, then it would lead to a worse future where more people die and the superheroes are exposed to the entire public instead. Said date happens to be the day of final exams, which is set to pass a few days after Finn's vision.
  • Fate/Nuovo Guerra has at least two so far, being an Alternate Universe story and all. More obviously, the destruction of Fuyuki City caused the Einzberns to pack up and move operations to Lucca, where the next Holy Grail War takes place. Less obviously, the lack of a living Shirou results in Luvia getting killed while fighting a Dead Apostle Ancestor by herself, as well as the very existence of the Edelfelt Sisters Lumi and Lempi.
  • Pokémon/Digimon Mon Wars is based on Digimon Adventure if Tai had chosen the Agumon card, leading the group to the Pokémon world right after the Kanto season.
  • Warhammer Fantasy Divided Loyalties, taking place before the "current day" of Warhammer Fantasy canon, starts with one nail already: the Elector Count of Stirland has died and the Player Character is selected to serve on the council of the new Elector Count. However the nails don't stop coming, as the butterflies from the PC's actions and larger events keep adding up. The quest has progressed far enough to practically be considered an Alternate Universe, with Sylvania now "East Stirland", Karak Eight Peaks successfully reconquered, and the deaths of several characters including Skarsnik, Gotrek Gurnisson, and Karl Franz.

    Tabletop Games 
  • The current default setting for GURPS is based on mixing this idea with The Multiverse to produce an infinite number of worlds. There's at least one canon parody of the concept with the world "Enigma" in which the only difference is the band The Clash never formed (and then the planet all humans on the planet disappeared without a trace in 1982).
  • During Magic: The Gathering's Time Spiral block, the middle set (representing the present) featured "alternate universe" versions of certain cards, primarily reprinting older cards into other colors that would best represent them if various mechanics hadn't been assigned as they were. Keeping in the spirit of "What if?", the flavor text on a good portion of the cards give quick looks at an entire subplot that revolved around what would've happened if Mirri had slain Selenia before Crovax had a chance to, thus fulfilling the terms of a family curse, turning her into a vampire instead of him.
  • In a nice scenario for a Dr. Who style RPG, the player's TARDIS comes to rest in the car park of a film studio. This causes John Wayne to have to find another spot so he is late and angry for his meeting to discuss playing Genghis Khan. Instead, Ronald Reagan gets the role and cancer-inducing radiation dose. President Wayne's foreign policy isn't a great success either.
    • John Wayne was a very heavy smoker throughout his life (at one point up to six packs of cigarettes a day!) and in 1964 nearly died of lung cancer (one lung was removed and The Duke needed supplemental oxygen for the rest of his life). Any contamination he might have received from the set of The Conquerer was likely just The Last Straw given what he'd already done to himself.
  • This is actually a means to become 'fragged' or disassociated from the right timeline in the time-travel RPG Continuum. You can destroy a time traveler by introducing a few of these little changes into his perceived timeline. "Replacing the nail" is a defense. Did an enemy time-traveler realize you sat in a coffee shop and read a book on Saturday, July 8th, 1995? He can frag you by doing something as simple as stealing the book out of your bag. You can reverse it by replacing a near-identical copy into your bag before "past you" notices the change. Screwing over a major historical event could bring down the wrath of any number of time travelers, all of whom find themselves affected by the change.
  • The true turning point of Clockwork And Chivalry's timeline is a Battle of Naseby that does not fall under this trope, differing from the real battle in almost every significant particular and ultimately ending in a bloody stalemate that leaves thousands dead and no clear victor, along with Fairfax MIA and presumed dead... but one of the most important changes to the battle and the course of history does fit this trope — The Earl of Carnwath is killed by cannon shrapnel, and is unable to prevent King Charles from engaging in his suicidal charge of the enemy forces, leading to his being captured and executed a full 3 years early following a trial that was even more swift and blatantly stacked against him than the real one, with both the lead-up to this and the aftermath of it leading to numerous changes in the course of history.
  • As one might expect, Sentinels of the Multiverse features several alternate realities. The nail for most of them is actually pretty hard to pin down with one exception: the Iron Legacy Timeline. In the main timeline, Baron Blade takes over the Wagner Mars Base in an attempt to trap and kill Legacy but Legacy never shows up. In the Iron Legacy timeline, Legacy does show up along with his daughter, who Baron Blade kills. This causes Legacy to snap and kill Blade. He then proceeds to take on the new identity of Iron Legacy and finally eradicate all crime and villainy by taking over the world. Somewhat ironically, the reason Legacy never shows up in the prime timeline is because he, along with the rest of the Freedom Five, was hospitalized after a fight with Iron Legacy who found his way to the Prime Timeline via dimensional portal.
    • There's also an identifiable nail that causes the distinction between the two split timelines (Sentinel Comics and Vertex) following the card game, which is whether or not Setback presses a button. Yes, really. To elaborate, the button Setback presses is a button on a fallen Chrono Ranger's badge which causes Chrono Ranger's AI, Con, to come forward to the present from the future, resulting in Chrono Ranger healing and Rook City, recently destroyed by OblivAeon, being somewhat un-destroyed. If Setback does press the button, OblivAeon remains in the timeline and things play out as normal and at the end there is quite a bit of hope, despite the destruction. If he doesn't press the button, Chrono Ranger stays messed up, Rook City stays destroyed, and the timeline splits and, since OblivAeon is a singular entity and thus there is only one of him, he does not stay in the timeline which results in things going dark and eventually the timeline being destroyed.
  • There are many important characters in the setting of BattleTech, but rarely does a single event have the potential to change the outcome of the entire universe. This is the case for Theodore Kurita's last-second decision to not shoot Frederick Steiner dead. A dead Frederick Steiner does not get handed over to Comstar denying them a skilled and politically astute military strategist for free and keeping their relationship with the Draconis Combine from further progressing. A dead Frederick Steiner does not disavow the soul-warping ambition of politics and become Anastasius Focht. Without Focht's even hand, Comstar's secret spy war with the Federated Commonwealth goes hot, the Primus gets into a spat with the Capellan Confederation, and the Free Worlds League declines to further integrate Comstar activity, escalating tensions and sowing further distrust of Comstar. When the Clans come calling, there is no Focht to be an ambassador to them, and without a proud and honorable warrior presence whom they can respect, Comstar is unable to earn the Clans' trust or learn their secrets. Without Focht, a series of inferior generals would likely make disastrous plays against the Clans or even suggest outright surrender by Comstar. The Primus would fall back on her usual backup plans and trick, trap, and sabotage the Clan war effort. The Clans, disgusted by the deceptive nature of Comstar, would not partake in the Battle of Tukayyid that stopped their invasion for 15 years. The Inner Sphere, distrustful of Comstar, would not come to their defense. Free to keep fighting as quickly as they could advance, the Clans could conquer large swaths of Inner Sphere territory, up to and including possible capital worlds such as Luthien or Tharkad. Denying the Inner Sphere the precious catch-up time of the truce, the Clans could easily conquer over a third of known space and forever alter the face of the Inner Sphere. In short, the entire timeline goes to hell if Frederick Steiner dies on Dromini VI.

  • A major plot point in Harry Potter and the Cursed Child. Harry's youngest son Albus and Draco's son Scorpius get their hands on a Time Turner capable of traveling back years into the past rather than mere hours. They want to use it to save Cedric Diggory from dying at the hands of Voldemort. Their meddling in history results in two alternate timelines:
    • The first timeline is caused when Albus and Scorpius disguise themselves as Durmstrang students to sabotage Cedric's attempt at the First Task of the Triwizard Tournament. Hermione spots them and suspects Viktor Krum of cheating, resulting in her not accepting his request to dance at the Yule Ball, going with Ron instead. Because of this, Ron never experiences any romantic jealousy over Hermione and never throws a fit about it towards her either. Instead, he continues to see her as a friend rather than a potential love interest. He does find love in Padma Patil and ultimately marries her, with the both of them conceiving a son named Panju. This makes Hermione an embittered woman who in her adult life becomes a Sadist Teacher at Hogwarts, venting her romantic frustrations at the students. Unfortunately for Albus and Scorpius, the changes to the timeline did not result in Cedric surviving, as his humiliation at the first task made him more determined at the other tasks.
    • The second timeline is caused when Albus and Scorpius successfully sabotage the Second Task of the Tournament. The humiliation of losing becomes too much for Cedric, resulting in him enlisting into Voldemort's Death Eaters. At the Battle of Hogwarts, Cedric manages to kill Neville Longbottom, who, in the original timeline, managed to destroy Nagini, Voldemort's final Horcrux. Because Neville was killed before destroying Nagini, Harry failed in his mission to kill Voldemort, resulting in Voldemort gaining absolute power. In this timeline, Harry was killed by Voldemort so Albus is never born. Also, Draco Malfoy has become the head of the magical law enforcement, with his son Scorpius being a somewhat important figure maintaining a reign of terror at Hogwarts, ran by Dolores Umbridge as headmistress. Also, Hermione runs an underground resistance movement with Ron and Severus Snape as members.

    Visual Novels 
  • By design, the entire story of a Visual Novel often relies on a player being given an option or two (and sometimes many many choices by design) that influence the way the game plays out and the narrative ends. Often what will let a character survive or place the narrative on a specific character route can be as simple as the MC picking the color blue instead of red.
  • In Cafe Enchante, an otome game, Misyr's route implies that Kotone's (the protagonist's) romantic involvement with the love interests ruins their lives in some way and results in the deaths of many that doesn't happen if she doesn't get romantically involved. The only exception is probably Canis' route, which plays out more or less the same. All of these examples start with Kotone inheriting a cafe from her grandfather and hanging out with one client more than the others.
    • The game implies that Ignis licking Kotone's wound at the beginning of his route started his Horror Hunger, which eventually gets so intense that he goes berserk and enters a frenzied state, which leads to him participating in his own kind's extinction, committing cannibalism, and eating a good chunk of Kotone's arm. If the protagonist goes after Misyr instead of Ignis, Ignis' Horror Hunger doesn't appear at all.
    • Il (and his associated side characters) undergoes much of the same character development and even overthrows the Evil God of his world in both his and Misyr's routes. The main differences are that, if Kotone gets romantically involved with Il, then Il is forced to kill against his will, gets his mind and personality wiped, brainwashed, and essentially gets his soul shredded in the process, leaving his mind broken in his route alone. Clearly, it's all a fitting punishment for Kotone helping Il with regular household chores at the start of Il's route.
    • In Rindo's route, Kotone helping Rindo's best friend buy a gift for his girlfriend helps him go over the edge and unleash a deadly monster unto his workplace, leading the deaths of an untold number of people and Rindo nearly dying. Rindo is then turned into an obvious non-human against against his explicit wishes. He loses practically every piece of his old life, including his apartment; his job; any activities or friends he had outside of the main cast and setting; and, by the end of his route, the lives of both his best friend and sister. None of this happens in Misyr's route, where everything is resolved peacefully and calmly instead, and Rindo isn't driven to brink of death.
    • Last but not least is Misyr himself. Kotone getting romantically involved with Misyr ticks off Big Bad Noah so much that he tries to destroy all worlds across dimensions. He succeeds at wiping entire regions of the various worlds that we know of and killing possibly trillions before he is stopped. Misyr is also permanently turned to a weak, mortal human and severely injured in his route. Noah does not try to end all worlds in other routes.
      • Misyr's route is extra special because the protagonist also ruins her own life in his route. Long story short, Kotone falling in love with Misyr puts her life in danger multiple times, gets her kidnapped multiple times by different people, her body destroyed, her soul merged with Noah's, and then becomes either planet or dimension, a process previously described as excruciating. At the end of Misyr's route, Kotone is no longer able to exist in her homeworld. She can at best override the cafe she and her beloved grandfather once cherished and roam, still trapped within the walls of the former cafe for the rest of her existence, as a ghost-like being for all eternity. All because Kotone went with Misyr to a bookstore in the common route.
  • The Bad Future in Clock Zero would never have happened had Nadeshiko, or rather, her alternate self, never been hit by that car at age 13 thanks to Rain's manipulations. Or better yet, had she not spoken to Rain at all in the first place in that timeline, the accident would never have happened in the first place.
  • Higurashi: When They Cry has a bad case of this; every arc it's something else in the initial factors—minor things like a man moving into the village or even Keiichi giving someone a doll—that sets off a completely different scenario of bloody tragedy.
  • In Umineko: When They Cry we have Lion, who appears in a fragment where Natsuhi accepted the baby that Kinzo gave her and didn't throw him/her over the cliff, therefore letting Lion lead a well-adjusted life and not growing up to be Yasu. Though ultimately subverted in that Lion is still murdered during the massacre...or so Bernkastel claims.
    • A subversion is mentioned in the Ep 8 manga where it is mentioned that even if Battler would have kept his promise to Shannon/Yasu, Yasu would have still thought him/herself as furniture and so it still wouldn't have saved him/her.
  • A large number of 'nails' exist in Nine Hours, Nine Persons, Nine Doors. Every possible choice- from Junpei's travel partners to whether or not you take a bookmark- influences your fate. Akane is watching them all unfold, to find the best fate for her to follow.
    • A little toy doll, of all things, ends up playing a pivotal role in Akane's backstory. While escaping the first Deadly Game with Seven, she dropped it and ran back to get it...which led to her getting caught by the murderous Zero and getting thrown in the incinerator room...which led to her Traumatic Superpower Awakening...which allowed her to establish a psychic connection with Future!Junpei...which saved her life...which meant that, several years later, she had to trap Junpei, herself, and eight others in a similar Deadly Game so Junpei could connect psychically with Akane's past self, fulfill the paradox, and ensure her survival. If not for that one important item falling at that one crucial moment, the entire game's events could have been averted.
  • Zero Time Dilemma reveals that everything in the Zero Escape series happened For Want of a Snail. If there hadn't been a snail in the middle of a jogging path at a particular moment in time, a jogger wouldn't have taken a different path to avoid it, she wouldn't have gotten murdered by a psychopathic little girl waiting on that path for a random person to kill, and an innocent man wouldn't have been wrongly accused of the crime. The man wouldn't have been arrested just before he could get into the taxi he called, and that taxi wouldn't have picked up a surgeon instead and gotten into a wreck, killing both the driver and passenger. A boy at the hospital who needed surgery wouldn't have died as a result of the surgeon never showing up. The innocent man's wife wouldn't have been so distraught by his execution that she commits suicide and orphans their two kids Aoi and Akane. Not being orphaned would have made those two kids a lot harder to kidnap and put in a Nonary Game, which would mean Akane wouldn't need to mastermind a second Nonary Game to prevent her own death in the first one. An old man who shared a hospital room with the boy who needed surgery wouldn't have taken inspiration from Akane to become Zero II and mastermind the Decision Game, which caused the Radical-6 pandemic that killed 6 billion people and required a third Nonary Game to be set up 45 years later in order to train Sigma and Phi in Mental Time Travel so they could go back and stop it.
  • Nails eventually decide which of the three routes you take in the opening of Fate/stay night. The best example is probably the choice leading to "Unlimited Blade Works": If Shirou recalls Saber before she slashes Archer, Archer is left unharmed and capable of participating in the Grail War at full strength. This in turn boosts Rin's position in the war, making her a competitor to Shirou instead of someone forced to rely on him as an ally (and also makes Ilya not notice Shirou). Thus, "Fate" and "Heaven's Feel" get locked out because everything begins snowballing from that decision
  • In Melody, the title character is giving her first concert under the aegis of Sharp Records. A nervous Melody turns to the protagonist for advice, at which point he can either give her a concrete piece of advice, or to simply say “just do your best.” Choosing the latter option leads to a failed concert due to Steve’s sabotage, then to Melody not standing up for Bethany when she comes to pick up the protagonist, to a bad ending.
  • Steins;Gate features a device that can send a text message into the past. While for the most part the characters make big, sweeping changes to the timeline, Ruka simply uses it to tell his mother to eat lots of vegetables during her pregnancy. This results in Ruka being born a girl, just like she wanted.
  • In Shall We Date?: Ninja Shadow, Toru Nakagawa's route has a small change regarding its very start: Makoto's decision to deploy the Action Survivor Player Character right from the beginning, instead of having her choose an instructor among the prospect boyfriends.
  • Ace Attorney is rife with this:
    • In the original trilogy, Justice for All, has a bad ending dedicated to this. The "nail" in the fourth case is the video evidence that Engarde had the intent to blackmail de Killer. Fail to present this, and the judge has no choice but to find Engarde not guilty, Adrian is sent to jail for a crime she didn't commit, Maya is set free but refuses to ever speak to Phoenix again, and Phoenix throws away his badge in disgust. Of course, if you present the videotape, then the exact opposite happens (Engarde gets thrown in jail, Adrian gets a reduced sentence, Maya is set free and returns to Phoenix, and Phoenix continues to practice law).
    • The sequel to Ace Attorney Investigations: Miles Edgeworth reveals that the main catalyst for the entire series, DL-6, happened because of a dessert making contest. Two contestants, a pastry chef named Dane Gustavia who was terrible at design and a sculptor named Isaac Dover who didn't know the first thing about dessert making, decided to cheat together and cover for each other's weaknesses. Gustavia would make the dessert and Dover would sculpt it into something impressive. Using this method, they both managed to make it to the finals. However, Gustavia had a dark secret. Despite being a chef, he suffered from a taste disorder that stripped him of all sense of taste, forcing him to use his son as a taste tester. He knew that the prize for the contest was a recipe book containing the recipes for various unreleased drugs and medicines, including a cure for his disorder, which is why he entered. When Dover learned of this, he betrayed Gustavia by forcing his own son to kidnap Gustavia's son, depriving him of his taste tester and removing him as competition, allowing Dover to coast to an easy victory since Gustavia had already made his dessert for him ahead of time. Gustavia was then forced to sneak into the contest host Jeff Master's room where the recipe book was kept and take pictures of the recipe for the cure he sought, where he was confronted by Dover, who planned to blackmail him over it. Gustavia simply killed Dover in response, and hid the body in Master's dessert sculpture, a pirate ship and treasure chest made of chocolate. However, another contestant, Delicia Scones, had been sneaking into all the rooms and sampling the desserts, weakening the supports holding up the pirate ship and causing it to collapse on top of the chest and break its lid, revealing the body for Master's assistant/adoptive daughter Katherine Hall to find. She took a photo of it and informed the police, but told nobody else so as to not disrupt the contest. Then, Gustavia, not realizing the body had been discovered, moved it because he respected Master as a fellow chef and didn't want him to fall under suspicion by having a body in his sculpture. He proceeded to hide it in Dover's own sculpture, that of the astrological sign Gemini made out of sherbert, by removing one of the twins and putting Dover in its place. However, the thing is, Dover happened to be Master's favorite artist of all time (though Master was unaware of this since Dover normally worked under a pseudonym). When Kate discovered this, she was afraid that the final work by the sculptor her beloved father loved so much would be destroyed in the police investigation, so she stole it and hid it away, not knowing his body was in it. No body to examine meant that the chief prosecutor, Blaise Debeste, had an autopsy report forged to make their investigation look legitimate; he passed it off to prosecutor Manfred von Karma as real, which prompted von Karma to force a confession out of Master, who was suspected anyway despite Gustavia's efforts due to the photo of the body Kate had taken. The defense attorney on the case, Gregory Edgeworth, had this secretly recorded and exposed von Karma's tactics, giving him his first and only penalty in his career. After the trial, Gregory and his son Miles got on the elevator with court baliff Yanni Yogi, but an earthquake hit the courthouse and the elevator stopped. After being trapped for hours, Yogi began to go stir-crazy from oxygen deprivation and fought Gregory, which led to Miles throwing Yogi's gun, the bullet that fired passing through the elevator door and hitting von Karma, who had just so happened to be standing outside; everyone in the car immediately lost consciousness, which gave von Karma the opportunity to open the doors, pick up the gun, and shoot Gregory dead in revenge for ruining his perfect record. It's hard to pin down any one event in this case as the "nail" because they're all nails. If even one of the events in that huge spoilered Wall of Text had not happened, DL-6 would not have happened either. Every single person involved in this case is an Unwitting Instigator of Doom. Hell, DL-6 wouldn't have happened if the Edgeworths, Yogi, and/or von Karma had just taken the stairs instead.
    • Spirit of Justice has a nearly-perfect plan to frame Trucy for murder in Case 2, which got thwarted due to Trucy's assistant getting her stage directions mixed up, forcing both of them to improvise live on stage to avoid breaking the planned illusion. This later forces the culprit to switch the panels of the prop coffin the victim was hiding in to make the alleged stabbing consistent and said assistant unknowingly having The Peeping Tom filming her from backstage and sending her a tape which neither the court or the true culprit knew about, revealing that a key piece of video evidence was edited.
  • Saya no Uta: Ultimately the entire narrative itself hinges solely on the fact that the main character, Fuminori, suffers a bizarre sort of Agnosia that even allows the narrative to play out at all. Had he not been in that car wreck and gotten hurt so specifically as to influence his condition, it's likely the story wouldn't have happened, as Saya would have been too monstrous for Fuminori to encounter.
    • One major point of the plot reveal is entirely Fuminori's fault and he isn't even aware of it. His quick planning and action at Ogai's mountain hideaway seemed like a good idea at the time, but ultimately ends up being the crux that Koji and Ryoko need to win. Had Fuminori decided to stab Koji as originally intended and not simply shove him down a well, Ryoko would have likely never investigated the well particularly thoroughly, and thus never found Ogai's notes on Saya (the same notes that help her come up with a trump card during the final battle). Because Fuminori decided to let the cold well kill Koji slowly from hypothermia instead of killing Koji himself, Ryoko shows up in time to save Koji and the two of them together kill Saya. All Fuminori had to do was stick to his original makeshift plan, but his new plan ultimately costs him everything in one of the endings.
    • The major choice that the player has to influence the ending is the phone call that Koji makes when at Fuminori's house. Calling Ryoko will allow Koji to "win" as Ryoko shows up to help, and calling Fuminori will result in the death of the planet. Neither ending is very positive, but ultimately the deciding factor as to which ending you get comes down entirely to Ryoko showing up and fighting in the final battle. Without this intervention, the ending is a bleak foregone conclusion.
  • WILL: A Wonderful World is built around manipulating the order and context in which some "nails" are hit in order to change the destinies of various people. Some of the earliest nails include where someone is when a lightbulb bursts, which person checks to see if a door is locked, and whether it's a traveler or a rookie cop that bumps into someone on the way to their destination.

    Web Animation 
  • Red vs. Blue:
    • Averted during Season 3. Church is blown back into the past and realizes that he can stop everything from happening. Instead, he just creates an army of Churches as he realizes that everything is set in stone. Because it was all his fault.
    • Season 10 goes to show that if Carolina had kept Sigma, her assigned AI and learned to accept that she wouldn't ever be able to beat Tex, Project Freelancer would have been spared a lot of pain and misery. Maine wouldn't have been reborn as the Meta, as Sigma wouldn't have been able to influence him; and she wouldn't have requested both Eta and Iota as AI, which means that Wash would never have received Epsilon and learned the truth behind everything, and South wouldn't have gone Cain and Abel on her twin brother.
  • Episode 12 of Inanimate Insanity II has Test Tube and Lightbulb accidentally time travel all the way back to the very first episode of Inanimate Insanity, different art style and all. Lightbulb's usual shenanigans cause Salt and Pepper to win that challenge instead of Lightbulb and Balloon, which causes the present day to become Inanimate Insanity Infinity, which implies that Salt and Pepper are hosting a never-ending object show purely for their own amusement.
  • Where Was My Hero...?: Miles "Tails" Prower tripped over a rock and thus never met Sonic the Hedgehog. It doesn't end well.

  • Erfworld Book 1 starts with this trope. The narrated opening scene shows the world's creators dropping one extra gem into a resource spot, which pays for an extra squad of units to go to field against Gobwin Knob's army, which is just enough to tip the balances in a heated battle, which means that Gobwin Knob's chief warlord gets an arrow between the eyes, which means that Gobwin Knob needs a new chief warlord before The Alliance shows up on their doorstep, which means that Wanda Firebaugh's bad day is about to get a lot worse. And then Parson blows up a volcano. Judging from the way the story is going, this was just the start.
  • In a time-travel example: the Schlock Mercenary time-travel plotline in Book 6 invokes this trope, but isn't itself an example.
  • Girl Genius: Despite his vigor, OTHAR TRYGGVASSEN Gentleman Adventurer! is actually pretty old. According to his Twitter, it turns out that he retired to an island for a few decades to live with his Geister wife, Oslaka, that he saved from the sewers in Paris. When she died, he left the island to find all of Europa in ruins and not a single person in sight. His consciousness was sent back to inhabit the body of his past self right before he saved Oslaka by an aged Tarvek to save the past somehow, so his presence will determine the course of the story.
  • Homestuck has innumerable offshoot timelines which all create elements necessary for the existence of the primary timeline. In one of those offshoot timelines, Karkat never runs the Mobius Double Reacharound virus. Without the virus (or some effect the virus had, such as possibly the deaths of the lusii), Gamzee does his From Nobody to Nightmare transformation much earlier than he was supposed to, and succeeds in murdering all of the trolls minus Aradia.
    • This also applies to the Alpha timeline; especially notable is the chain of events starting with Gamzee placing a harlequin doll in John's bedroom on Prospit, which ultimately leads to Jack Noir destroying the Kids' universe.
    • Once John gains his Retcon powers, he uses them to turn the events of the past few thousand pages—in which things steadily went From Bad to Worse, culminating in the session going completely Off the Rails and most of his friends dying in the events of [S] Game Over—into a doomed offshoot timeline. In the new main, "alpha" timeline he creates, the changes he made, many of them rather small, cause drastic differences that affect the protagonists significantly for the better: Terezi never spirals into self-loathing and her Destructive Romance with Gamzee never happens, Vriska doesn't die and her influence prevents many of the worst parts of the Game Over timeline from occurring, and Aranea never gets the chance to steal the Ring of Life, resurrect herself, and enact her insane plan that killed most of the protagonists in [S] Game Over.
  • In General Protection Fault, the Nega-Verse is what would happen if Nick and Ki were evil and acted on Nick's fantasy of taking over the world that was discussed in a brief arc early on. There are smaller examples, such as Nega-Trudy being as selfish as Trudy Prime until her mother's request for her to find her sister (something Trudy Prime didn't hear about until after her Evil Plan failed) changed her for the better.
  • Parodied in this strip of Tom the Dancing Bug. Percival Dunwoody wonders if he caused the people of 2012 to turn into fly-men when he stepped on a twig in the Paleozoic; it turns out that he actually did it by killing off all the humans in 2011 and injecting flies with human DNA.
  • One plotline of Stand Still, Stay Silent can be traced back to Emil throwing a wing mirror he had broken off the Cat-Tank a little too hard. The mirror landed on the head of a guy that was labelling crates and ended up swapping the labels of two crates in the confusion before passing out. One of the crates was food for the main cast's expedition, the other was full of candles. The swap is not discovered before they are in an isolated area and have gone past a Point of No Return. Mission Control gets a merchant ship to deliver them some new food. Aboard said merchant ship is a sheltered sheepherder who really, really wants to see the world and has just realized that getting hired as an unpaid kitchen aid on a merchant ship was not working towards this objective as well as he hoped. Said sheltered sheepherder then notices two food crates being prepared for delivery and has a lightbulb moment. Due to not being immune to the illness that is a very serious threat in the area the main cast is exploring, they can't just send him back and end up having to watch him on top of their existing duties.
  • In Sailor Moon Cosmos Arc, because Usagi and the others chose to be reborn through the Galaxy Cauldron, Crystal Tokyo is founded in the 30th century, rather than the 21st century as in canon. This also had an effect on Chibiusa, as despite never awakening as a Sailor Senshi, she still aged to adulthood normally. It's revealed that in the process of being reborn, Usagi had secretly wished Chibiusa would never awake as a Senshi so she could live in peace. The comic deals with the ramifications of that spoiler.
  • In Saturday Morning Breakfast Cereal: "A Reason" talking to God, who's naturally The Omniscient, reveals that "everything happens for a reason" — and all the reasons are stupid and random.
    "And how my son hates me?"
    "A single point mutation in a single sperm's DNA caused by a stray ion emitted by some banana pudding you ate the day he was conceived."
  • A comic from Secret Lives O Mobs has some dwarves discovering a funny rock in orc territory. Then the orcs attack them. Then the dwarves get revenge on the orcs, then orcs on the dwarves, and so on until weeks later there's a giant Final Battle for the dwarven race's existance.
  • GF Serendipity: The divergence point between the fic and the series is that Fiddleford McGucket and Stan Pines chance upon each other and become business partners before Ford would consider asking for the former's help with the portal.
    • Stan and Fiddleford became millionaires and now head one of the biggest companies in America.
    • Ford never tried to ask for Fiddleford's help.
    • Ford traded his hands to the Hand Witch for her help with the portal. It still doesn't work and he now has skeletical hands made of alien metal from the spaceship he found during his research.
    • Ford is so isolated from the rest of Gravity Falls the residents not only don't mistake his twin for him but don't even figure out they're related.
    • Ford still sees Bill Cipher as a muse and never hid the Journals.
    • Stan is so famous the residents of Gravity Falls know of him in spite of not knowing the reclusive scientist who lives there is his twin brother.
    • It's Ford who has a mullet instead of his brother.
    • Ford's dressed like the crazy old man Fiddleford became in canon and also has a beard.
    • Fiddleford decides not to make his memory-erasing gun.
  • In Narbonic, the difference between the Bad Future and the good one is that, at a certain point, Dave, forewarned by his alternate future self, refills an inground swimming pool. The water, by breaking a fall, allows Artie and Helen to survive, and Helen's presence keeps Dave from rampaging and starting a nuclear war. The war, together with Helen becoming a brain in a jar due to her injuries, and Mel's single-minded quest to undo this timeline, result in a really all-around grim future, all hinging on the presence of water in the pool at that moment.
    • Also, one date when he was a teenager resulted in him becoming a heavy chainsmoker in one timeline, and a non-smoker in another. When he mentally time travels back into his teenage self on the day of that date, he screws it up even worse that it was before, and as a result is now a lifelong non-smoker.
    • What are you talking about, Dave never smoked!

Alternative Title(s): Butterfly Effect


How Linda Met Bob

Linda tells the kids that Bob's mustache is how they both met and it caused her to break up her engagement with Hugo.

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Main / ForWantOfANail

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