A story in which one small change has a ripple effect, resulting in massive changes.
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 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, 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 trope is a Sub-Trope of this itself. 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.
- 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.
- 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.
- For want of Raye Penber, Death Note lasted much shorter than it could.
- Even earlier than that, the human who picked up Ryuk's fallen Note happening to be both crazy enough and smart enough to use it constantly without getting caught initially.
- The first two live-action films showed that the whole second arc could have been avoided if L thought to write his own name in the Death Note.
- In Delicious in Dungeon, mistakes on their map cost Team Touden a day of dungeon delving, and a trap caused them to lose three day's worth of food. The party was not at their best due to hunger when they encountered the red dragon, causing Falin to be eaten, and the start of our story. Had things been otherwise, there likely would have been a very different fight with the dragon. Considering their reduced party, with Senshi admitting he's not much of a fighter, were able to kill the dragon without any deaths later, they likely would have been very successful.
- The basis for the plot of Dual! Parallel Trouble Adventure is that reality splits depending on whether a construction worker on site when Lost Technology is found takes a sample home when his crew's ordered to destroy the evidence. The Hero, Kazuki is at first able to see into the other reality, and eventually crosses over.
- The reboot of the Rozen Maiden manga features Jun, the protagonist of the original manga, who decided to take the blue pill path instead, resulting in him not meeting the dolls and remaining a hikikomori for the remainder of his mid-school duration. We meet him as a disgruntled college student with a bad side job, and frequently being laughed at due to his past status as a hikikomori. That is until Shinku and the other dolls from the original continuity appear in his continuity...
- One of the recurring themes in Legend of Galactic Heroes, where seemingly minor events cause a huge impact on history. What if Kircheis had been armed during Ansbach's assassination attempt and survived instead of died? What if the supply depot Muller attacked had fought back instead of surrendering so that he couldn't rescue Reinhard? What if Hilde hadn't persuaded Mittermeyer to attack Heinessen to force a ceasefire, or if Yang ignored said ceasefire? What if Yang hadn't allowed the "Imperial escorts" on his ship so that they couldn't assassinate him?
- In the Mai-Otome manga, Sergay is not Nina's father and Nagi, while not a very good person, is not the main antagonist. As a result, Nina stays on the heroes' side for the entire story.
- On a lesser scale, Sergay is not anonymously paying for Arika's education in the manga, forcing her to take on several side jobs and leaving her no time to study, at one point putting her in danger of failing and dropping out.
- In Dragon Ball Z, the main timeline ends up being VERY different than the one Trunks comes from. For example, Androids #17 and #18 are much more powerful in the main timeline but not really all that evil (they do initially intend to kill Goku out of boredom but don't really go out of their way to hurt anyone else) whereas in the future timeline, since Goku was already dead, they were made explicitly for world domination but were far less powerful because they did not account for Super Saiyans. Android #19 didn't exist in the Trunks' timeline nor did Android #20 (Dr. Gero had never turned himself into an Android). Goku also got sick much later than he did in Trunks' timeline.
The difference in strength between the main and alternate timeline versions of #17 & #18 was explained differently in the manga. In the "Trunks: The Story" chapter when Gohan was fighting #17 & #18, immediately before #17 kills Gohan, #17 tells him that he'd been using no more than half of his power. After a short timeskip, we see Bulma & Trunks debating the need for a time machine. Trunks thinks he's already gotten strong enough to defeat 17 & 18, while Bulma thinks he's too naïve since he was only at about Gohan's level and Gohan was still killed. After this we see Trunks leave to fight them and the next panel we see they've put him in the hospital. There is no actual proof that the full magnitude of 17's power (and possibly also 18's) was revealed to Trunks before he went back in time. Assuming that Trunks was unaware of 17 & 18's full power in his timeline, it would explain his surprise at their power in the main timeline. This would also indicate that the androids from the main timeline were actually just as strong as those in the alternate timelines and that Trunks was simply unaware of that fact. However, one thing remains consistent in both timelines: Goku dies.
- In Blood+, Saya and Diva are twin sisters. Joel raised Saya like a daughter, whereas Amshel kept Diva locked in a tower, treating her like an experiment. When Saya receives this history lesson, she can't help but sympathize with her sister, knowing full well that they could just as easily wound up with their roles switched.
- As revealed in Mobile Suit Gundam Unicorn, just about everything that's happened in the Universal Century, from the Earth Federation's MO to the One Year War and beyond, could be traced in some form or another to the Laplace incident in UC 0001.
- Puella Magi Madoka Magica: During Episode 5, Sayaka laments not contracting earlier, wondering aloud if doing so would have saved Mami's life. The Different Story reveals that yes, it would have. However, this is not necessarily a good thing.
- The series in general happened because in the original timeline, Homura was saved from a witch by Madoka; when the latter died fighting Walpurisnacht, Kyubey granted Homura's wish to rewind time and protect Madoka out of pity. This begins the timelines that eventually result in Madoka becoming a Goddess, and eventually, Homura becoming a demon.
- All the events of Tokyo Marble Chocolate would never have happened if the pet store hadn't mixed up the delivery of the pet animal Yuudai intended to give to Chizuru; instead Chizuru would have broken up with Yuudai right at the beginning.
- Ranpo Kitan: Game of Laplace It's the driving plot device behind the events.
- The prequel arc of The Irregular at Magic High School reveals that nigh everything that happened in the main story is the result of Tatsuya smiling at some friends he happened to meet while guarding Miyuki, his sister. This makes Miyuki realize that 1: her brother has emotions and is in fact a human being just like her (although their family considers him The Un-Favourite), and 2: he has never, ever smiled like that at her. He's closer to those people than he is with his own family. And then Miyuki starts to really question why that is, and to realize how bigoted her family is. This starts the chain reaction that led to her and Tatsuya becoming friends and (successfully) rebelling against their clan, who are a major national power. And none of that would have happened if Tatsuya hadn't smiled, or Miyuki hadn't seen him do it, or his friends hadn't attended that party, or if their elitism had overwhelmed their affection for him.
- The titular character in Naruto has a moment where he reflects on this trope, stating that if events had been slightly different, he and Sasuke could have ended up switching places in the story, as the two were Not So Different.
Naruto: "You know, Sasuke, there's a chance our roles could've been reversed."
- However, if we talk about the trope, then almost all the events of the series could be avoided if Obito Uchiha never fell under the rocks.
- The entire plot of Horimiya can be traced back to Hori's little brother Souta tripping when he was scared by a dog. If it wasn't for that, Miyamura wouldn't have had any reason to walk him home. Hori never would have seen what Miyamura looked like outside of school, meaning the two of them never would have become friends or fallen in love, and Miyamura would still be a social outcast.
- My Next Life as a Villainess: All Routes Lead to Doom! is about an ordinary Japanese schoolgirl who finds herself reincarnated as the main villain of an otome game, and sets out to avoid the bad endings in store for her if everything follows the original script. For all her efforts, all it really takes to go from a despised Rich Bitch to a beloved heroine is being a decent human being; by giving the rest of the cast the emotional support they desperately needed, she helps them develop into better people and ends up charming every single one of them (even the girls), effectively pulling off a wholly unintentional Hostile Show Takeover.
- The series does it to itself in the spin-off subtitled Verge of Destruction Chapter. In the original novel, Catarina regains her memories of Earth when she's a child, giving her a seven-year head start on the events of the game. In the spin-off, she doesn't regain her memories until after the game has already begun, which leaves her panicked that it's far too late to try and save herself.
- The whole of UQ Holder! is an alternate universe to Mahou Sensei Negima! in which Asuna didn't get sent back in time, resulting in a much worse series of events. To give a brief summary, in both universes Asuna went into stasis to stabilise the Magic World until it could be permanently stabilised by a separate plan. In the Negima universe, Asuna was sent back in time (after coming out of stasis) to the series' present. This greatly raised her friends' spirits which, combined with her unique power, allowed them to defeat the Lifemaker, save Nagi (who was being possessed by the Lifemaker) and carefully reveal magic to the world. In the UQ Holder universe, Asuna was never sent back, her friends were not able to properly defeat the Lifemaker, the Lifemaker took Negi as a new host, several of Negi's allies were brainwashed into pawns or killed, and society has numerous problems due to an imperfect integration of magic.
- The creator of Ouran High School Host Club points out that if Haruhi and the Host Club members had never met Tamaki, their lives would've been drastically different and profoundly more unhappy, since it's his presence and influence that encourages them to address their character flaws and grow positively as individuals. To elaborate; the twins would've become completely emotionally insulated from everyone but each other, Kyoya would've become more of The Sociopath as he insisted on only doing what would benefit himself, Mori and Huny would've stagnated as people, and Haruhi wouldn't have learned how to relate to and deal with people, which would've caused her to fail at her dream of being a lawyer without understanding why. In addition, without the formation of the Host Club, all of the people they helped would've been left to deal with their problems on their own (and they weren't dealing with them well).
- In the backstory of Boarding School Juliet, inclement weather sparked a conversation between two people (Chiwa and Turkish) who would never have spoken otherwise due to their differing races and classes. They hooked up, were discovered, and bullied into dropping out of school and returning to their respective nations much earlier than planned...where they got married to other people and had children who are the series' protagonists. (Chiwa sees the parallels, and thinks they're awesome.) These shenanigans are also a nail in themselves because if Romeo's mother were any Towan other than Chiwa, she would've ended her son's also-Secret Relationship when he accidentally revealed it to her.
- According to an interview with Hugtto! Pretty Cure's director, the series actually ran on this, but we only saw small snippets of it in-series. According to the director, the future where Hugtan, Harry and the Big Bad of the series came from was a timeline where Hana never transferred schools. Because she remained in such a hostile environment, she never bothered to better herself and the only real friend she had was the main Big Bad George. This also meant that Saaya, Homare, and Emiru never broke away from their poor situations as well. It's heavily implied that this combined with the stresses of being a Pretty Cure caused Hana to be Driven to Suicide.
- In The Asterisk War:
- If Haruka didn't get seriously injured, Ayato would never have gone to Seidoukan Academy to search for her; he wouldn't have befriended Julis, Lester, Saya, Kirin, or Claudia; he wouldn't have obtained Ser-Veresta; and he wouldn't have defeated Kirin to become the top-ranking fighter at Seidoukan and free her from her uncle's grasp.
- If Lester hadn't attempted to bully Ser-Veresta into compliance, it wouldn't have caused the weapon to go berserk and Ayato wouldn't become its rightful owner.
- If Ernesta hadn't sent out Silas to take out the strongest students at Seidoukan to win the Phoenix Festa, Julis wouldn't have been kidnapped, Lester wouldn't have realized Silas's true colors, Ayato wouldn't have rescued her after being tipped off by Saya and Claudia, Arlequint would never have been discovered to be behind the assassination attempts, and the deal between Arlequint and Seidoukan wouldn't have gone ahead.
- In High School DXD:
- If Azazel didn't have Raynare murder Issei because of his Sacred Gear, not only would she not go out on a date with Issei, but Rias wouldn't have transformed him into a Devil after he was fatally wounded, he wouldn't have befriended Asia, Raynare's plot to steal her Sacred Gear would've never been discovered, and Azazel wouldn't have joined the Occult Research Club.
- If Zeoticus didn't arrange for Rias to marry Riser, not only would Issei not have his Engagement Challenge, but Rias would've never continued to pursue her relationship with Issei, and Ravel wouldn't have transferred to Kuoh Academy and joined the Occult Research Club.
- If Diodora hadn't stabbed himself and had Asia heal him, she wouldn't have been exiled from the Church as a heretic, she wouldn't have formed a friendship with either Issei, Xenovia or Irina, and Diodora wouldn't have been curb-stomped by Issei.
- If Xenovia and Irina would've just found the Excalibur swords by themselves instead of teaming up with the Occult Research Club, Xenovia wouldn't have encountered Asia, the truth that God Is Dead wouldn't have been discovered, Kokabiel wouldn't have captured by Vali, Xenovia wouldn't have been excommunicated from the Church as a heretic and befriended Asia, and Kokabiel's plans for the Great War would've gone ahead.
- Azazel sent Baraqiel on a mission, only for the latter to be wounded, discovered by Shuri Himejima, and have their daughter, Akeno. If Shuri wouldn't have been killed by her own relatives, Akeno wouldn't have disowned her father and joined the Occult Research Club, and she ultimately wouldn't have started a relationship with Issei.
- If Azazel didn't negotiate a peace treaty between the Fallen Angels, Angels and Devils, the Khaos Brigade would've never been discovered, Vali wouldn't have gained a rival-turned-friendship in the form of Issei, the youkai wouldn't have formed an alliance with the devils, Yasaka wouldn't have been rescued by Issei and Sun Wukong wouldn't have helped Issei defeat Cao Cao.
- In Chivalry of a Failed Knight, if Stella hadn't transferred to Hagun Academy, she might not have met Ikki and lost in the mock battle with him, which resulted in her becoming his girlfriend.
- In The Testament of Sister New Devil, if the man from the hero village didn't steal Brynhildr, not only would Basara's Traumatic Superpower Awakening might have been avoided, but most of his fellow friends wouldn't have accidentally been killed by his Banishing Shift, and he wouldn't have been exiled.
- Aladdin: If Jafar hadn't attempted to kill Aladdin after he found the lamp, Abu wouldn't have stolen it and then bit Jafar. Because of this, Aladdin became the genie's master rather than Jafar. This eventually leads to Jafar's own demise at Aladdin's hands as well as a complete change in Aladdin's fate where he goes from a poor unknown thief to the future sultan of Agrabah, something Jafar had wanted to become with the lamp. Years of planning and searching amount to someone else getting his coveted prize all because he wanted to screw Aladdin over.
- In Cars 3, Lightning McQueen is enjoying his time as a Piston Cup champion when all of a sudden, a rookie named Jackson Storm appears out of nowhere on the last lap and overtakes him for the win. Because of this, several veterans are replaced by new high-tech racers like Storm, and Lightning eventually loses control at the last race of the season, resulting in a horrible crash. The owners of his sponsor, Rust-eze, decide to sell the sponsor to a businessman named Sterling, who builds an elaborate training center so he can make a comeback. But upon causing damage to the equipment, Sterling considers retiring Lightning in favor of becoming a spokesman for a brand, but Lightning begs for one more chance. Sterling agrees on one condition: if Lightning doesnt win the first race of the new season in Florida, he has to retire. Over the course of the movie, fellow trainer Cruz Ramirez helps him in many ways, and he eventually discovers her dream to be a racer as well. When the day of the Florida 500 arrives, Sterling shows up and pesters Cruz to come back to the training center because shes not a racer. Lightning hears their argument over the mic, inspiring him to let Cruz take over for him mid-race to prove Sterling wrong and let her fulfill her dream, even if it means giving up his bet.
- In Justice League: The Flashpoint Paradox, Barry Allen A.K.A. the Flash, wakes up to find his world turned upside down. Thomas Wayne is Batman instead of Bruce, Superman doesn't exist, and the world is on the verge of ending due to a war between Atlantis and Themyscira. At the film's climax, it's revealed one change in the past resulted in this Bad Present; Barry went back in time to save his mother's life.
- In Monsters, Inc., Mike forgets to file his paperwork on time, and can't get it in himself because he has a date with Celia. Mike can either go back and get the paperwork but lose his restaurant reservation and therefore his dinner date, or proceed with dinner and risk getting fired for not filing his paperwork. Because of this, he sends his friend Sulley to get it. Sulley then finds a door to the human world that shouldn't be there, and through that door comes a little girl. Sulley and Mike hide her in their apartment, and their attempts to get her back uncover a conspiracy by Monsters Inc. CEO Waternoose to kidnap children to solve the city's energy crisis.
- In the Direct-to-Video Our Friend Martin, a teenaged African American boy, his white best friend, and two other kids, another white boy and a Latina girl, go back in time to save a teenaged Martin Luther King Jr. after learning that he was assassinated. When they come back to the present, the Civil Rights Movement never happened and as a result, the protagonist's "best friend" angrily tells him he doesn't talk to "negroes", Jim Crow laws are still in effect, the Latina girl works as a cleaning girl alongside her mother and doesn't speak English, the feminist principal now teaches home-ec., and doesn't respond to the principal's sexist insult. When he goes home, he learns that his mother, a self-employed businesswoman, works as a maid. Things only go back to normal when King decides to back in time, and accept his role in history.
- Shrek: Farquaad is so into his idea of how to get Fiona and make her his queen, he refuses to listen to the Magic Mirror when it tries to warn him of Fiona's curse. If he had, he wouldn't have sent Shrek to rescue her, thus nothing else in the series would have happened.
- Shrek Forever After: Rules Lawyer and borderline Jerkass Genie Rumpelstiltskin offers Shrek a Deal with the Devil. Shrek gets one day as a lawless ogre in exchange for one day from his past. Rumpelstiltskin takes the day Shrek was born, thus creating a world in which Shrek never existed. One of the biggest changes is the fate of Fiona, who without anyone to save her from the tower chose to Screw Destiny and simply escaped by herself. In addition, in this universe Far Far Away is a dystopia ruled by Rumple- since Shrek wasn't alive to rescue Fiona in the nick of time, the king and queen were tricked into signing their kingdom to Rumple.
- In The Simpsons Movie, there literally is a nail involved, as Homer was working to hammer down a nail on the roof. The entire plot wouldn't have happened if Bart didn't laugh at Homer lodging the hammer's claw into his eye. Angered at how his own son would dare laugh at his own father's pain, this led to Bart trying to rationalize his laughing out of Homer's signature strangling of Bart's neck, which led to Homer daring Bart to skate naked to Krusty Burger, which led to Homer finding a pig at Krusty Burger, which led to Homer keeping the pig as a pet and choosing to dump the pig's wastes into a lake, leading to a catastrophe where the head of Environmental Protection Agency and film's villain, Russ Cargill, tried to bomb Springfield for desire of a clean, sanitary and unpopulated area. In the end, Homer and Bart are not only back to square one, but now they have to rebuild their entire house, not just repair the roof.
- In Toy Story 3, as when Andy grew up and was about to go to college, he put all his toys (save Woody) inside a bag to store them in the attic. However, Andy's mom mistook the bag for garbage and put it next to the garbage cans, leading to all the toys except Woody into thinking that Andy outright tried to get rid of them and so they wanted to stay at Sunnyside Daycare Center, where new children will play with them and the leader there Lotso appeared friendly and welcoming. However, later on, Andy's toys are assigned to dangerous infants who play rough and Lotso turns out to be a sadistic bully who wants them to be tortured, if not broken to death. Once the toys do figure out a master strategy to escape their prisons, Lotso drags them all with him into a garbage chute where they nearly get burned and destroyed by an incinerator.
- Heck, Andy deciding to have one last play with his toys in Toy Story 2 not only leads to him obtaining Jessie, Bullseye, and the LGM, but also leads to their lives being saved when Lotso betrays them to the incinerator, thanks to Mr. Potato Head saving the LGM's lives. The person who had a delivery from Pizza Planet should be thanked as well.
- Blind Chance is an example of Alternate History at the individual level. Have one small detail play out differently (catching or not a train while noticing or not someone in the crowd), and the man's entire life will change as a result. The way how the entire story is told inspired the next two movies listed below.
- Lola rennt (a.k.a. Run Lola Run): the wildly variant endings of Lola's twenty-minute "Groundhog Day" Loop can all be traced back to Lola's reaction to the boy with the dog on the staircase.
- Sliding Doors has catching/not catching a train as the "nail" and ends with dramatically different versions of the protagonist. The 'nail' moment was marked with music and later in the film when the protagonist had to make a decision the music was played again. Although we didn't follow this 'split' it implied that there were more points where a single decision would be important.
- In the movie Frequency, a son manages to send a message back in time and save his firefighter father's life. However, because of this change, his mother, who was a nurse, never left the hospital to make funeral arrangements and so was on duty to save the life of a man who would've died. This man turns out to be a serial killer who kills the mother and is now still at large in the present of the son.
- The vast majority of Brazil's plot occurs because of a swatted fly that fell into a typewriter, causing an arrest warrant for Harry Tuttle to instead be made out for Harry Buttle.
- The whole "Pottersville" sequence in It's a Wonderful Life is an example of this. George's having never been born turns out to have an indelible effect on the lives of pretty much everyone he's ever known in real life. (Of course, the whole idea of the movie is how much one man can make a difference.)
- The Back to the Future film trilogy is a series of nails showing what would have happened if a certain event did or didn't occur:
- In the first movie, Marty McFly's father was a wimp who couldn't stand up to the bully Biff Tannen, but after Marty changed events concerning his father in 1955, he becomes a more confident and successful man who has Biff eating out of his hand, and Marty's family life has also improved.
- Also in the second movie, an automobile accident that would have happened in the third movie when Marty was racing with his friend Needles was the nail that caused Marty's future history to go down the toilet by 2015, eventually resulting in him being fired from the company he and Needles were working for. When the accident was avoided in the third movie, the YOU'RE FIRED message that Marty's girlfriend/future wife Jennifer Parker had received from the future was erased, meaning that their future could potentially become a better one.
- Pointed out by the scriptwriters in the Audio Commentary of Pirates of the Caribbean: The Curse of the Black Pearl. The entire plot is basically kicked off by a corset being laced too tightly, causing the wearer of the corset to fall into the water, causing the cursed coin she's also wearing to summon the undead pirates who capture her, setting off the rescue mission by the other two main characters that makes up most of the plot.
- The Gods Must Be Crazy: Because a pilot throws an empty Coca-Cola bottle out of an airplane... a primitive tribe abruptly discovers civilization.
- A Nightmare on Elm Street (1984): Nancy's mother explains that the reason Freddy is on the loose is because he was supposed to have been arrested, but his warrant was never signed in the right place, meaning he got off right then and there and the parents of Springwood were left to take matters into their own hands...
- Star Trek:
- The Narada being sent back through time causes a divergence, creating a brand new timeline in Star Trek (2009). James Kirk's father dies by suicide-charging his ship into it, James himself is born in space rather than Iowa, he and Spock do not meet on the best of terms, and Vulcan is completely destroyed.
- This continues into Star Trek Into Darkness, where Khan/John Harrison is found and awakened almost a decade before he was originally, and Starfleet is in no condition for the coming war with the Klingons (when the emergency is called, only about a dozen captains and their Number Ones are present at the meeting). It's also implied that the Praxis incident happened much earlier than expected, possibly due to misuse of technology obtained from studying the Narada.
- ...and on into Star Trek Beyond where due to one species not accepting a peace offering from another and forcing Kirk to keep the artifact in question, the Enterprise (NCC-1701) is destroyed some 22 years before it did in the original timeline and the Enterprise (NCC-1701-A) is commissioned roughly over 20 years sooner as well.
- In The Adjustment Bureau small things make big ripples in fate's plan.
- Invoked by Al Pacino's character in Any Given Sunday to light some fire in his players at half-time (see the quotes page).
- The Lord of the Rings, as is mostly canonically adapted from the books (though occasionally not), bounces the outcome of its story backwards and forwards through the many separate applications of this trope within its work. Here are the lost nails, in numerical order:
- 1. Sauron, with his left hand firmly holding the Idiot Ball (as well as his mace), extends his right hand — the one carrying the Ring of Power — out to Isildur.
- 2. Isildur, apparently catching the Ball as Sauron throws it, keeps the Ring.
- 3. Deagol finds the Ring while fishing.
- 4. Smeagol loses the Ring, allowing Bilbo to steal it.
- 5. Merry and Pippin, having stolen produce from Farmor Maggot, bump into Frodo and Sam as they run.
- 6. Frodo decides to travel through Moria instead of scaling Calahdras.
- 7. Merry and Pippin disinterestedly disturb the waters outside the entrance to Moria.
- 8. Pippin knocks a skeleton down a well within Moria.
- 9. Galadriel gives the Fellowship several gifts.
- 10. Aragorn advises Theoden to spare Grima Wormtongue.
- 11. Smeagol dips in the Forbidden Pool.
- 12. Pippin finds one of the Lost Seeing Stones at the foot of the Tower of Orthanc.
- 13. Orcs argue about the distribution of Frodo's possessions.
- X-Men Film Series:
- X-Men: Days of Future Past: The Bad Future faced by the cast of the original trilogy all came about due to the assassination of Dr. Bolivar Trask in 1973.
- X-Men: Apocalypse: Because of the changes to the original timeline, the public is aware of mutants nearly three decades earlier. This leads to En Sabah Nur gaining a cult, Agent Moira MacTaggert investigating it, and the ancient mutant waking up when he otherwise didn't.
- A petty argument about a character's choice of decoration snowballs into a full-blown race riot in Do the Right Thing. Buggin' Out attempts to start a boycott on Sal's pizzeria because Sal won't put up pictures of black people on his Wall of Fame. He succeeds in getting Radio Raheem and Smiley on the protest, and they begin protesting Sal, which led to Sal breaking Radio Raheem's radio, which led to Raheem's attack on Sal, which led to the cops showing up and killing Radio Raheem, which led to Mookie starting a riot by throwing a trash can at Sal's pizzeria, which led to the pizzeria being burnt down...over some pictures. Everything that happened in the spoilered part was bad, but none of it would've happened if Buggin' Out wasn't so insistent on the pictures.
- In 2009: Lost Memories, Korea and Japan's (and by extension, much of Asia's) future hinges on the survival or assassination of Ito Hirobumi in 1909. In the Alternate Timeline most of the movie takes place in, Hirobumi survives, Japan goes on to retain most of its colonial holdings (including Korea), and becomes an ally instead of an enemy to the Allied Powers in World War II — which results in the nuclear bombs being detonated in Berlin instead of Hiroshima and Nagasaki.
- The major conflict of the second half of Project Almanac. When they first fired up the machine, it blew the power on the street which caused the school's star basketball player to get run over and get his leg broken. Since he was benched, the team never made it to the championship, and those that would have attended went elsewhere instead. One particular parent was a pilot, who ends up crashing a plane and killing a lot of people as a result. David's frantic attempts to correct for this only further makes a mess of things.
- Retroactive: Karen keeps having to travel back through the time machine to stop Frank from murdering his wife because each loop keeps getting worse. She goes back 20 minutes and ends up in the same place each time in Frank's car after he picked her up, but her different attempts to stop him (warning the Sheriff, stealing Frank's gun, etc.) only result in Frank going on an even bigger killing spree. She eventually decides to go back to before she got in Frank's car, which results in Frank turning on his partner and getting shot by Rayanne.
- Alexander and the Terrible, Horrible, No Good, Very Bad Day: Alexander drops his brother Trevor's pacifier in the sink, Ben accidentally turns on the garbage chute that destroys it, causing Trevor to cry all night, forcing Emily to rehearse for her play in the cold car, making her extremely sick; forgetting to turn the lights off which drains the car of its battery and making Kelly late for work the next day. And Ben being forced to look after an extremely unhappy Trevor makes his day and job interview a nightmare and he embarrasses himself at a Japanese restaurant meeting. Only Anthony's next day was not directly affected by the pacifier accident; instead, this was tied to an argument with Alexander that led to a miscommunication with his girlfriend, causing them to nearly break up and him getting detention, failing his driver's test and wrecking the family car trying to fix things up. Also, he gets a zit.
- The Final Destination films each involve premonitions allowing people to escape a mass disaster, only for Death to come after everyone who should have died according to "Death's design". The second film leans heavily on this trope; it's revealed halfway through that the first film's characters avoiding the Flight 180 crash created ripple effects as Death hunted them down, allowing others to escape their fates. (For example, one character in the first film is hit by a bus, which means that one of the passengers on that bus doesn't make it to the hotel she was planning on staying in that night, which means she survives when a gas leak suffocates everyone else in the hotel) It's implied (and was explicit in the original script) that the highway pile-up in the second film was arranged by Death to take out a number of these 'ripple survivors' in one go.
- In the final film of the series, the final scene reveals that the film is a prequel, and that the Flight 180 disaster was a means of catching up to two survivors of an earlier bridge collapse, meaning that if those survivors had been a little bit slower escaping the bridge, the first two movies wouldn't have happened.
- However, the fourth film (and the most recent events in-universe) reveal that actually this isn't a result of this trope but was in fact Death's plan for each person all along. The premonitions were Death's way of making sure that the protagonists survived long enough to reach their intended deaths.
- In Hot Tub Time Machine, the bar bet turns into a nightmare for Lou. The squirrel that was vomited on in an earlier scene changes the history of the NFL playoff game as it disrupts John Elway's pass on the field.
- The beginning of Tajomaru's story in Rashomon starts like this: he was drifting off to sleep in a forest, but is awakened by the sound of hoofbeats and opens his eyes to see the samurai and his veiled wife passing by. He initially isn't interested, and drifts off again when a breeze stirs his hair and lifts the veil of the woman, causing him to want her, and from there, the events snowball into a murder which results in the trial. He blames the whole incident on the breeze revealing the woman's face and rousing him to view the face. Admittedly if the samurai hadn't stopped to inspect this strange, half-clothed man reclining by a tree at the edge of the forest road and kept moving, the breeze would have arrived later and Tajomaru wouldn't have given the couple a second thought.
- At the start of The Shawshank Redemption, Andy Dufresne contemplates murdering his wife and her lover but instead throws his gun away after sobering up and deciding not to murder them. They're murdered by someone else and Andy is charged. Andy's only defense is he couldn't have done it because he threw his gun in the river. Had he not thrown away his gun, the bullets recovered from their bodies would have proven his gun was not used to commit the crime. This is actually pointed out by the District Attorney.
- In Money For Nothing, Joey, while being driven home by his friend when there was not enough work at the docks, sees a metal bin that would make a nice toolbox and has his friend stop. The bin turns out to be from an armoured car and contains two canvas bags with $1.2 million meant for a casino. Joey takes the bags and leaves bin. Had he also taken the bin, the police would never have found out where and how the money left the truck and thus been unable to question the two kids who saw everything, including the make and colour of Joey's friend's car, and likely would never find Joey. However, the ending states the real Joey was acquitted on a plea of temporary insanity, so he wasn't thinking right.
- In Spider-Man, this idea is particularly strong. If Peter Parker had not had a crush on Mary Jane Watson for most of his life, he wouldn't have had to work up the nerve to talk to her at Columbia's science lab (sowing the seeds of later friendship and romance), which also means he wouldn't have lingered long enough to be bitten by the GM spider. He wouldn't have had his conflict with Ben or the fight with Flash Thompson, he wouldn't have gone out for the wrestling show, he wouldn't have let the thief go, and Uncle Ben would not have been killed. Despite the upside of the Parker family not losing Ben, the seminal events of Spider-Man's origin would never have happened, leaving New York without its most iconic superhero. This potentially means that Norman Osborn would still have become the Green Goblin, but there would have been nobody capable of stopping him. (Not as important, but he also never would have gained the confidence he needed to confess his feelings to MJ as Peter or save her life and catch her eye as Spider-Man, and however dragged out, they wouldn't have gotten together.)
- Much of the above applies to The Amazing Spider-Man with the added wrinkle that if Peter had never worked with Curt Connors in recreating the OO formula, Connors would never have been able to turn himself into the Lizard. Had Peter still become Spider-Man, this means the defining moment where he goes from vigilante to hero would never have occurred (though he might have succeeded in catching Ben's killer). Interestingly, while Captain Stacy's death by impalement at the claws of the Lizard never would have happened, his profession meant that there could always have been another day he didn't make it home to his family.
- In Spider-Man: Far From Home, the only reason that Peter managed to discover Mysterio's deception is that he accidentally fired his web on an Attack Drone which led to MJ picking it up and led them to discover the fact that the Elementals were in truth, illusions created by Mysterio's crew. Had Peter fired his web just a little bit off the mark, or if MJ hadn't walked out of the concert to follow Peter, the crew would have recovered the drone and Mysterio's scheme of becoming the next Iron Man would have gone off without a hitch, and Peter would have likely retired from being a superhero in favor of having a normal life, having passed down the E.D.I.T.H glasses as well as the title Tony Stark's successor in favor of Quentin Beck.
- Molly's Game: Had the pinestick that resulted in Molly's freak accident been in any other position or any other angle, chances are the accident, and Molly being involved in organizing poker games would've never happened.
- The plot of Rewind (2013) revolves around three time-travelers attempting to undo a chain of events that led to New York City being destroyed: in 1929, a poor young man is desperate for money to take care of his little sister. He turns to crime but is caught. As he sits in jail, his sister dies of tuberculosis while in foster care. Having nothing left to live for, he falls into a pattern of alcoholism and drug use, committing robberies and muggings to feed his addictions. During one mugging, he accidentally kills the young wife of a brilliant scientist. The scientist never recovers from this heartbreak, turning cold and bitter. When the scientist hears about an experimental time travel technology, he builds a bomb and takes the city of New York hostage. The scientist does not care if New York is destroyed, because he knows the time travel technology will be used to save the city - and possibly his wife in the process.
- In the Christian movie Second Chance, the lead character, who is a Christian, sees all the fun his friends are having apart from him and wishes that he never was a Christian. An angel shows and says his prayers have been answered, and thus in his new non-Christian life, he sees that his parents are divorced, his mother is going out with other men constantly, and his friends see him as a sleazy jerk who is always sleeping around. During a scene where he is being chased by a few guys and desperately prays for his life to be restored, he reaches the doors of a church and finds out that the guys chasing him became his friends again, thus indicating that he was now given a second chance.
- In a brief moment at the beginning of The Fugitive, Richard Kimble's friend Charles Nichols returns his keys to him and thanks him for loaning him his car. Not until the end of the movie does Gerard realize and tell Richard that Nichols used the keys to let the one-armed man into Kimble's home. Kimble laughs bitterly at this, realizing that his wife would still be alive had he not done something as common as loaning his friend his car.
- In a cruel irony, this also saves Kimble's life while simultaneously contributing to his ordeal—had he not received an emergency call from the hospital, he would arrived home with Helen and likely been murdered along with her. The call saved his life, yet left him alive to be accused of killing her.
- The musical movie adaptation of Oliver Twist. The famous scene where Oliver asks for more food came about only because he'd happened to draw the shortest straw among the boys.
- While Fargo would probably still have ended badly for nearly everyone concerned in the long term, it starts to really snowball out of control because Carl made a simple mistake and forgot to switch the getaway car's plates. This gets three people killed and leads to the police getting involved, causing the plan to become doomed in a much faster and messier way than it otherwise might have been.
- The Phantom Menace: As confirmed in the Disney EU, Qui-Gon Jinn's death in a Naboo power plant at the end is the singular event that cemented that Anakin Skywalker's path would be to the Dark Side.
- Tales from the Hood 2: Pretty much the crux of "The Sacrifice". The old man explains to Henry that if Emmett Till chooses to live instead of die then his sacrifice will never occur and the civil rights movement will not progress to the point where Henry has a choice at all.
- In Avengers: Endgame, retrieving the infinity stones via Time Travel and resurrecting everyone only happens because a rat ran across Ant-Man's control panel, bringing him back discovering how to travel through time.
- 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.
- 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
- In Norse Mythology, Freyr is doomed to lose the fight to Surtur at Ragnarok because he gave his good sword away to Skirnir.
- 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.
- Pokemon 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.
- 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 planetall 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.
- 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.
- 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 introduces the biggest Nail in the Zero Escape series: a snail on the road. Had a young mother not avoid the path with the snail on her jogging route, she wouldn't have been killed by a little girl and gotten an innocent man falsely accused of the crime. He wouldn't have been avoided by his taxi driver, who in turn wouldn't have gotten into a fatal car crash with the surgeon he did pick up, killing the boy who would have been operated on in the process (who himself wound up the inspiration for Sean). The man's wife wouldn't have been so distraught by his execution that she commits suicide and orphans their two kids Aoi and Akane, which in the long run would have led to a lack of 6 billion man viral body count and a lot less Nonary Games.
- 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
- 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 two talented chefs; Isaac Dover and Dane Gustavia, decided to cheat together in a dessert competition, Dane being the one handling the ingredients and taste ending up to not being able to taste anything. He knew that one of the prizes contained the recipe to a cure for his taste disorder, only for Isaac to find out and blackmail him over it, leading to himself getting murdered to keep the secret, thus Case IS-7. Had Isaac not found out about this or at least their roles in the scam had been switched in the first place, Gregory Edgeworth wouldn't have had Manfred von Karma investigated and penalised for evidence forgery, leaving him without any intent for murder and Edgeworth not being a prosecutor under his wing, ultimately leaving Phoenix no reason to practice law.
- Even if IS-7 did occur, DL-6's bizarre circumstances wouldn't have taken place if Manfred just took the stairs.
- 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 a 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.
- 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.
- 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.
- Parodied here on Chainsawsuit.
- 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.
- 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.
- This Subnormality strip. If you look closely enough, the last panel nearly spells out this trope.
- 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.
- Squigly calls a butterfly a murderer for producing such effects, and then imagines his own effects.
- Squigly predicts this for a cocoon, who thinks "Cool!". Later Buddha fixed it, though.
- In Freefall, they blame Sam rather than a butterfly.
- 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."
- The Bishop Barron video "Stephen Colbert and Providence" demonstrates the way God can work to create incredible effects from small things by following an intergenerational chain of thought.
- Barron begins by tracing the joy Stephen Colbert found in faith after the accident that killed his two brothers and father to this quote, "Are not all of God's punishments also gifts?"
- He traces that quote back to an obscure letter by J. R. R. Tolkien responding to a question about Character Death's connection to real death.
- Tolkien in turn only had that wisdom because the orphan Tolkien was taken in and educated by a priest named Father Morgan.
- Yet Morgan only knew that God's punishments could be gifts because he was educated in the Birmingham Oratory, founded by John Henry Newman.
- John Henry Newman was an Anglican priest who was rejected by English society when he converted to Catholicism and kept at arms-lengths by wary cradle Catholics. Alone in the world, Newman discovered an abandoned oratory and began to educate there, using his experience of rejection to teach people to find joy in pain.
- In summary, without Newman's lesson, Morgan would never be able to comfort and raise the orphan Tolkien, who would never be able to use his spirituality to create the world of The Lord of the Rings, which would never be able to comfort a young Stephen Colbert, whose comedy could never comfort and save people maybe not even born yet.
- In Counter Monkey, Spoony recounts the "Leaping Wizards" incident wherein he was serving as DM for a Dungeons & Dragons module for the RPGA. Reading through the module, he found a particularly pathetic ambush by three wizards, each with a single spell. Knowing the encounter would be a cakewalk, he altered each wizard's spell so that, rather than each having the default Magic Missile, it was a variety of Sleep, Charm, and Ray of Enfeeblement. Through a combination of this change and some lucky rolls, the vastly outclassed wizards killed two party members before going down... much to the displeasure of the RPGA, as the module was intentionally weak to prevent player deaths.
- Fear, Loathing and Gumbo on the Campaign Trail '72: John Julian McKeithen, a former governor of Louisiana, decides to stand for the 1972 Democratic nomination instead of George McGovern. A more moderate figure than McGovern that can appeal to a wider audience, he wrangles with Nixon for months before Nixon decides to withdraw for the good of the country and allow him to become President. Soon afterward, he dies in a plane crash. Things only get worse from there.
- A Giant Sucking Sound: Ross Perot is able to win the 1992 election first by not withdrawing in August, and by choosing Jerry Brown as his running mate.
- The 4chan imageboard /co/ had a thread that speculated what would happen if Bruce Wayne's parents never died. The result? Bruce and a certain fellow named "Jack Napier" end up becoming best friends, Gotham City goes through a golden age, and the readers cried manly tears.
- 4chan's /tg/ board does this as well, some of the more recent ones, the crusades are won in the third crusade, the slew of changes involve a massive Kingdom of Jerusalem, The Library of Baghdad still stands, the reconquista never happened to its fullest extent, and the rising heresies move the reformation in a very different direction (Cathars, Flagellants and Waldensians rather than Anglicans, Calvinists, and Lutherans.) And these are the most normal things to come from it.
- This Macworld article warns that solid-state drives are sometimes not all they're cracked up to be, as they can be even more unstable than hard disk drives at times. Each data cell in an SSD can only be written to so many times before it gives out, and most of the time that takes years, but the author admits his Macbook Air crapped out after only a month because of this very issue, which is why he wrote the article (he had no backup at the time). Basically, solid-state drives sort of know that their cells can give out for any reason, and so 10-20% of the cells included in an SSD are meant as remedy cells for use when others give out... but once that remedial supply is gone, any further cell failures are totally gone too. He writes that once this happens, the drive can simply refuse to boot up at all, meaning that if you want any shot at fixing the drive, you have to format it... losing everything on it forever. You can't retrieve data from an SSD the same way you can from an HD, because on the latter the data is not really deleted once you move to delete it, but on an SSD for data to be recognized as deleted it has to actually be deleted.
- According to Plumbing the Death Star's "Why Is the Death Star Spherical?", putting a friendlier management on the Death Star and renaming it the "Love Sphere" would make the Stormtroopers more open about the Death Star's structural problems; this would allow the Empire to cover up the exhaust port, allowing them to destroy Alderaan, the Rebellion, and Luke while derailing the entire Star Wars saga.
- Rage by Guy Collins Animation starts with a butterfly extinguishing a man's last match, which triggers a chain of rage-inducing events that ends with an Earth-Shattering Kaboom.
- SCP Foundation: On January 13, 1917, an 11-year-old boy is waiting with his mother for his father, who had just returned home from Europe. In one timeline, she held his hand and the two barely managed to avoid a speeding car. In another, she had brought a present for his father, which allowed the boy to run out into the street in excitement and the car to hit him. His parents mourn him, but history moves on. The biggest difference is that the organization the boy would one day found never comes into being. Welcome to Unfounded.
- Channel Awesome's Fanscription series is a "What if?" series that talks about how things would have played out if big events in film history took a different turn.
- In Rocky IV, the premise of the movie is that Apollo Creed is killed in the ring by Ivan Drago and that Rocky then challenges Drago to a rematch in Russia to avenge his friend. But what if Apollo hadn't died? What if Rocky, not wanting to see Apollo's pride lead to his deathnote , threw in the towel before Drago could land the fatal blow on Apollo?
- Apollo is hospitalized and while he recovers, he is permanently paralyzed and confined to a wheelchair. Rocky visits Apollo in the hospital, but Apollo is angry at Rocky's decision to throw in the towel and kicks him out of the room. Frustrated, this leads Rocky to turn his anger and frustration on Drago. Apollo eventually understands why Rocky made his choices and reconciles to travel with Adrian to Russia to be by Rocky's side while Rocky is training. Apart from some minor alterations, the main plot is the same up until the bout with Drago in Russia, which Rocky enters in much better spirits than in the movie.
- The grudge match between Rocky and Drago goes slightly differently, with Drago getting the upper hand on Rocky in the opening rounds, enough so that Apollo considers throwing in the towel before Rocky meets the same fate as him, at least until the tides change and Rocky takes away Drago's advantage. It's words of motivation from Apollo (mixed with some of Tony's lines) that give Rocky the final push to win over Drago by TKO.
- Fanscription did another video highlighting how Rocky V would've differed as a result of the above changes to Rocky IV. The what-if in this case also borrows elements from the later movies.
- Rocky hangs up his gloves after the Drago match due to the potential brain damage he sustained. Five years later, Rocky's fortune is wiped out thanks to his shady accountants and he has to move back to his old neighborhood.
- Tommy Gunn's storyline is consolidated with that of Mason Dixon from Rocky Balboa and Union Cane from Rocky V. Tommy has been with his promoter George Washington Duke for several years, and the crowd is not impressed by how easily he wins fights. The heavyweight division's reputation is on the outs, and with Duke in command, many of Tommy's fights aren't 100% legitimate. Duke and his partner Merlin begin thinking of a way to regain public support, ultimately deciding to pull Rocky out of retirement.
- Apollo has been doing charity work since the physical injuries from his bout with Drago ended his boxing career. His reputation has been very much restored. During a press conference, he's asked about Duke's pitch.
- Duke does everything to try to goad Rocky into the match with Tommy Gunn. When none of this works, he sees an article about another charity event Apollo is overseeing and gets an idea. He calls a press conference and exposes Rocky's criminal record to the public. Not only that, but he also reveals the truth about Apollo's son Adonis. Apollo's and Rocky's reputations are tarnished. Apollo reaches out to Adonis and he decides to take him in.
- Rocky and Paulie are accosted by Duke and Tommy at a bar as a publicity stunt. Rocky decides he's had enough and agrees to the match. He goes to the Pennsylvania Athletic Commission and reapplies for a boxing license (as seen in Rocky Balboa). The panel is hesitant but is swayed in Rocky's favor by his motivational speech. He has a falling out and shouting match with Adrian and Robert over going back into the career that crippled his friend, and ultimately reconciles with Robert. He decides that the match with Tommy will be his last fight before he retires from boxing for good.
- There's lots riding on the climactic exhibition match, as Rocky and Apollo are seeking to restore their reputations and Rocky needs to get out of his financial hole. The match goes twelve rounds, with Rocky winning over Tommy by TKO in the twelfth.
- The ending scene of Rocky and Robert at the Rocky statue, where Rocky gives his son Rocky Marciano's cufflink. Except here, Apollo, young Adonis, and Tony are also present.
- In Rocky IV, the premise of the movie is that Apollo Creed is killed in the ring by Ivan Drago and that Rocky then challenges Drago to a rematch in Russia to avenge his friend. But what if Apollo hadn't died? What if Rocky, not wanting to see Apollo's pride lead to his deathnote , threw in the towel before Drago could land the fatal blow on Apollo?
- The Magic, Metahumans, Martians and Mushroom Clouds: An Alternate Cold War timeline is built on the premise that the paranormal is discovered to be real during World War II, and is then heavily researched and adapted by both sides of the Cold War, while also becoming prevalent on its own. Quite a few changes compound over the years as things play out.
- Beria is executed by Stalin in 1945 for trying to disprove the OSP's (the Soviets' paranormal research organization) efforts by shooting Renzaoren (a Ridiculously Human Robot found in a crashed alien ship).
- For unspecified reasons, Centralia is never destroyed by its underground coal fire.
- Thanks to the intervention of Prometheus and Typhon, the monarchists lose the Greek Civil War, turning Greece into a communist state.
- Because of how things turned out in Greece, America provides more aid to the Kuomintang, allowing them to win the Chinese Civil War, reducing the PRC to just Manchuria. This also means that without a communist superpower at their back to support them, North Korea never invades the South.
- Trofim Lysenko is purged by Stalin for opposing the Soviet use of mysticism.
- Thanks to having golems boosting their regular military forces, Israel does well enough in the Arab-Israeli War to take and keep control of the Sinai Peninsula and Suez Canal. This causes a more embittered and paranoid Naguib to crack down on potential rebellion, including executing Nasser before he can overthrow him.
- The Nationalists winning the Chinese Civil War helps prevent the Red Scare. As a result of this, Eisenhower stays out of the Republican primaries in 1952, causing the nomination to go to Robert Taft, who then loses to Adlai Stevenson. Party fatigue then allows Nixon to win in 1956.
- Subhas Bose never dies in a plane crash, and goes on to take over India after becoming a metahuman. Even after his death, his followers stay in control, keeping India as a dictatorship.
- South Africa's imposition of apartheid leads to a native rebellion spearheaded by metahumans and shamans, which successfully overthrows the white minority government.
- The collapse of Churchill's reputation (from his obsessive search for Excalibur) allows Anthony Eden to take over leadership of the Conservatives years sooner. He also become Prime Minister a few years ahead of OTL due to public fear after a metahuman gangster's rampage.
- The US provides the Batista government in Cuba with the Lazarus zombie virus, which enables them to crush Castro's revolution. Conversely, attempts to use zombies to remove Francois Duvalier's regime fails due to Papa Doc fighting back with his own Voodoo Zombies, solidifying his regime; in response to the Americans' actions, Duvalier seeks closer ties to the Soviets, leading to Haiti taking the place of Cuba in a resulting missile crisis.
- Stalin survives his 1953 stroke due to the intervention of Koschei the Deathless (who was freed by the OSP and brought into Soviet service), going on to carry out several more purges, including a mini-pogrom against the Jewish population over the "Doctor's Plot" and executing Kruschev and Zhukov on Koschei's advice. When he finally does die in '58, Malenkov has him revived via Brain Uploading, only to pull the plug when this results in insanity and a nuke being launched at Moscow. With Malenkov's reputation ruined and much of the government dead from radiation poisoning, Dmitri Shepilov takes over as General-Secretary.
- Martin Luther King is murdered in 1957 by a metahuman Klansman.
- Without the Red Scare, Joe McCarthy's witch hunts are instead built around supposed Satanic influence in the government.
- The 1953 Iranian coup is prevented due to Mosaddegh getting a warning about it from the afterlife.
- Similarly, the 1955 coup against Juan Peron is averted due to people being more focused on the alien parasite outbreak in Patagonia.
- Nicolae Ceausescu's obsession with eliminating Romania's vampire problem at the expense of all other political matters eventually leads to a Military Coup in 1973, ousting him in favor of Ion Mihai Pacepa.
- The French with the Battle of Dien Bien Phu thanks to the paranormal research at their disposal, and are able to get Kai-Shek's China on the anti-communist side in the war.
- Nixon is assassinated in 1964 by a metahuman associated with the Vietnamese communists. His Vice-President, Harold Stassen, wins the subsequent election by a landslide, only to then lose against JFK in '68.
- Pol Pot never changes his name from Saloth Sar, drifts more towards mysticism than communism, and eventually turns himself and his followers into Nagas to give them an edge against the French.
- The chaos that engulfs Paris in May 1968 — partly due to existing tensions from both the left and right wings but primarily because of an invasion from an Alternate Universe where the Bonaparte dynasty conquered the world — weakens people's faith in Charles de Gaulle and leads to him losing reelection later that year.
- Syngman Rhee is never ousted as President of South Korea, due to a precognitive warning him of the coup. Instead, he ends up making himself the face of a new Christian movement led by Ahn Sahng-hong, who later creates a youth serum for him. The Americans eventually try to enable a pro-democracy coup against him, and when it fails he cuts an alliance with North Korea, keeping both nations separate politically but united against foreign intervention in their affairs. Rhee even shares the youth serum with Kim Il-Sung.