If you've got a story that needs a protagonist you can either have them be a chosen one, where forces have already pre-determined who is to be The Hero that saves the day (eg. prophecy, bloodline, it's their field of work, etc). Or, you can just toss an Inciting Incident onto a random street corner and let the first Tom, Dick or Harry who comes across it be the protagonist.
To qualify for this trope, the protagonist needs to meet these two terms:
- Not have any inherent qualities or circumstances that make them the hero beforehand.
- Find the Inciting Incident, and not have the Inciting Incident start happening in front of them.
So, for example: Meet our protagonist, Alice, about to take a nap by a river. She notices a rabbit with a pocketwatch hurry past her, and since that's not something you see every day Alice decides to follow the rabbit. The rest - well, you know the rest (or maybe you don't, but what happens next isn't important). Why is Alice the protagonist? Because she saw the rabbit. If her sister had been the one who saw the pocketwatch-wearing rabbit and followed him, we'd likely be reading Alice's Sister's Adventures in Wonderland.
On the other hand, if the rabbit had come up to Alice and asked her to come to Wonderland to stop the evil Queen, that doesn't count - for that, see Summon Everyman Hero. Neither would it count if the evil Queen invades our world and there is nobody around but Alice to close the portal so the rest of the Queen's army doesn't get through - for that, see Right Man in the Wrong Place.
(There's also "Die Hard" on an X, which would be if Alice was part of a trans-dimensional police force and was called into Wonderland because the evil Queen had illegally seized power and was now holding everyone in the palace hostage, but we digress.)
This trope is commonly seen in works with a Story Arc or Myth Arc to serve as the protagonist's Origin Story, such as where a superhero got their powers. As a bonus, exposition can be given much more naturally, since in this case our main character knows as much as the audience does and other characters will explain without invoking As You Know. For works where characters stumble into the conflict time and time again, common in episodic works, instead of being a one-off, see sister trope Plot Magnet and Unlikely Hero.
How the protagonist responds also varies. They might go From Nobody to Nightmare as a result, they might just go along for the ride as a Pinball Protagonist and be an Action Survivor. For the latter, it's common for our protagonist encountering this trope to have various reasons reasons why they can't escape from it now that they've stumbled into it, for example a Clingy Macguffin or Trapped in Another World. If it's a superpower-related Incident, expect I Just Want to Be Normal.
The Drifter archetype often follows this pattern: he comes into a new town and tries to keep to himself, but ultimately gets sucked into some local conflict that didn't initially have anything to do with him.
See also: Accidental Hero, when somebody finds themselves regarded as a hero without intending to; Awakening the Sleeping Giant and Create Your Own Hero, both for when a person or party creates - from their point-of-view - the antagonist via actions they themselves have made (in which case they might be a Heroic Neutral); Innocent Bystander, for characters by the wayside.
Supertrope to Falling into the Cockpit, for when the Inciting Incident happens to be the soon-to-be protagonist encountering a Giant Mecha; It Began with a Twist of Fate, which mentions a specific decision that led the protagonist to the Inciting Incident. Not to be confused with Stumbling Upon the Lost Wizard.
- Rokuro "Rock" Okajima from Black Lagoon is forced to go on the run and eventually, live in Roanapur and join Lagoon Company since his boss in Asahi Industries decided to have him written off despite being told to handle sensitive data to be given to a VIP in Southeast Asia in case He Knows Too Much.
- Seras Victoria, a police officer, joins Hellsing since she was targeted by a vampire and Alucard turned her into one in order to save her life after being wounded in a fight. Since the agency had publicly declared her as "dead", Seras has no choice but to work for them.
- In Nana Moon, ordinary girl Keke finds herself in Moon Haven and in the occupation of being the moon genies' guru by complete happenstance. She is on her way to a concert when a comet passes by and has an effect on the elevator she's in, resulting in her being teleported to the moon.
- The Runaways became caught up in Secret Invasion because they just happened to be visiting New York City on the very day that the Skrulls attacked the city.
- In King Ottokar's Sceptre, Tintin finds a lost briefcase on a bench in a park and decides to return it, initiating his involvement in the whole Bordurian conspiracy to depose the Syldavian monarchy and invade Syldavia.
- The Black Island similarly has Tintin thrown into the plot when a counterfeit money smuggler's plane crash-lands in a field near where he's taking a walk.
- Cars 2: Mater finds himself in the middle of a conspiracy when an intelligence exchange goes awry and Mater gets mistaken for a master American spy.
- Emmett, of The LEGO Movie, finds himself caught in a government conspiracy when he trips and falls down a hole, finding the Clingy Macguffin that could stop the Doomsday Device by the Big Bad.
- In Spider-Man: Into the Spider-Verse, the Peter Parker of the story's universe once told Mary-Jane that anyone could have been Spider-Man. Miles Morales just happened to be the kid who got bit.
- The Big Lebowski: The Dude comes home one night to find two men, who rough him up, and pee on his rug, before figuring out he's the wrong guy. Realizing they were looking for a millionaire, like him named Jeff Lebowski, he goes to see the guy about replacing his rug.
- Keys to the Kingdom plays with this in regards to Arthur Penhaligon. While he is The Chosen One for receiving one of the Keys, him being chosen was him being in the wrong place at the wrong time, where he was one of many of a list of children who were close to death (in his case chronic asthma). The villain, Mister Monday wished to grant ownership of the Minute Hand to the boy and then reclaim after he died off. However he didn't consider not only would Arthur be saved from death by the Key's healing powers, but also that Arthur would choose to use the Key to fight back against his forces and be a hero.
- Jack and Annie, of The Magic Tree House, find the titular tree house walking home from school one day and begin their Time Travel adventure shenanigans.
- A Tale of Time City: Vivian, escaping from the Blitz during World War II London, suffers from a case of Mistaken Identity and is taken to Time City.
- Often happened to Biggles in stories set in the Genteel Interbellum Setting: A typical example would open with Biggles and his friends looking for a new freelance gig and being offered a seemingly innocuous contract to deliver someone or something, which would then go badly awry in some way (often but not always involving Sky Pirates) and leave them having to solve some mystery or criminal conspiracy almost as a side effect of extricating themselves from whatever predicament they'd landed in as a result.
- Doctor Who:
- Most of the companions simply happen to stumble into the Doctor's vicinity and now have aliens trying to kill them.
- Donna Noble is a semi-exception as she was looking for the Doctor; however, it was spurred by her accidentally getting sucked up into the Doctor's TARDIS a year ago.
- Likewise, Gwen Cooper stumbled into Torchwood via similar stumbling into the Torchwood team.
- Rembrandt from Sliders got caught up in Quinn's parallel world surfing adventure because he got caught up in their whirlwind while driving his car and, like the rest of the team, are trying to get back.
- Assassin's Creed IV: Black Flag: Unlike most protagonists of the franchise, Edward Kenway simply happened to get shipwrecked next to an assassin, getting him involved in the titular creed.
- The PC in Dragon Age: Inquisition just happened to have been at the Templar-Mage peace summit when the explosion destroyed it. Becoming the only survivor, somehow gaining the ability to seal rifts to the fade, and getting swept up in the game's plot from there. During "Here Lies the Abyss", it is revealed that the Inquisitor literally stumbled upon Corypheus's plot during the summit. Hearing Divine Justinia's cries for help, and walking into the middle of his ritual. Disrupting it and gaining the mark in the process.
- The Elder Scrolls:
- The Elder Scrolls IV: Oblivion's protagonist is in prison and happens to cross paths with The Emperor, who is trying to escape assassins, thrusting them into the main quest of preventing The End of the World as We Know It.
- While the protagonist of The Elder Scrolls V: Skyrim is a chosen one there are a few side quests that invoke this trope:
- When the player enters the city of Markarth they encounter a murder taking place, getting caught up in a conspiracy involving the Silver-Bloods and the Forsworn.
- The player, as a student from the College of Winterhold, triggers a trap by picking up a necklace that eventually leads to them encountering an Artifact of Doom. It's even lampshaded by one of the NPCs that under normal circumstances the College would not send a random student back to inform the Arch-Mage.
- Far Cry 3: Jason is suddenly thrust into the position of having to save the Rook Islands and his friends from Vaas when they're kidnapped during a vacation.
- In Final Fantasy XII, main character Vaan was just a Street Urchin and petty thief who happened to be trying to steal a valuable piece of Magicite from the castle on the same day that both the deposed princess and a famous Sky Pirate also tried to steal it, resulting in the urchin getting entangled in a political struggle that reshapes the continent, and even forever changes the relationship between mortals and the Occuria, who are awfully close to gods.
- Tommy Angelo from Mafia: The City of Lost Heaven is an honest taxi driver as the game opens, when he is forced at gunpoint to help a couple mobsters escape from a rival family's attack. Later on, the same rivals destroy his car in revenge, so he has no choice but to join up with the family he unwillingly helped before.
- The Playa from the original Saints Row is just a Stilwater nobody at the outset, accidentally caught up in a three-way gang shootout and almost executed as an unwanted witness. He is rescued by the Vigilante Man Julius Little and joins his 3rd Street Saints out of gratitude, as well as to Clean Up the Town.
- This is pretty much how every single mainline Pokémon game happens. An average pre-teen gets their very first Pokémon, they go around catching 'em all and beating a few Gyms for a while, then they find themselves in the midst of the latest villain's heinous scheme with little warning, and suddenly they're catching Legendary Pokémon and stopping anything between a mafia boss and The End of the World as We Know It. Ironically, Pokémon Sword and Shield subverted this for once, and the result is generally considered a weaker plot than previous games because of it.
- Marble Hornets: Jay is just a man with a camera who decides to look back on old memories of shooting a never-finished student film when he notices something weird in the background of every tape. The supernatural effect on him is so strong he is unable to stop his obsessive investigating afterward- even after he makes the attempt to stop completely, he gets pulled back in through circumstances beyond his control.
- Katara and Sokka from Avatar: The Last Airbender, who found Aang (whom is The Chosen One) frozen in an iceberg.
- Dipper Pines from Gravity Falls, who finds a mysterious journal buried in the woods when sent out to hang signs on trees. The journal, as a Great Big Book of Everything, tells Dipper that the town he's in - the titular Gravity Falls - contains a variety of supernatural phenomena, piquing Dipper's interest and leading him to start exploring the hidden secrets the town has to offer.
- In King, Russel Wright finds a portal hidden under his bed and discovers a land called Under, where he is deemed king because he's from "the place where kings come from" (our world).
- The four protagonists of Super Noobs, who got entrusted with defending the Earth with battle balls (that don't come off due to being fused with their DNA) due to being mistaken for soldiers.