Every Scar Has a Story

"Well, you look nervous. Is it the scars? You wanna know how I got them?"

—Joker, The Dark Knight

Many times, when an author wishes to identify a certain character as a Badass, said character will be given some sort of horrific permanent disfigurement. Most of the time, the disfigurement will stay unnoticed, possibly out of respect for he that is marked, or because the story behind it is too horrible for the others to imagine. But there always exists the chance that some bystander will ask about the scar, in which case the Badass is contractually obliged to explain it. When he is, expect the story to be long-winded, fantastical, and involving at least one Crowning Moment of Awesome. In other words, a Remember When You Blew Up a Sun? moment.

Similar to Scar Survey, but can occur between any two characters (not just hero/heroine) at any time (not just after sex.)

For further scar-y goodness, see Covered with Scars, Good Scars, Evil Scars, Scar Survey, and Scars Are Forever.

Examples of Every Scar Has a Story include:

Anime and Manga

In Ghost in the Shell: Stand Alone Complex, the character of Gouda Kazunto gets a chance to explain the particular disfigurement of his head, which includes a somewhat iconic pointy shape.
- Then, in Second Gig, Saito tells a group of poker players how he lost his eye.
Naruto has Ibiki Morino, whose scars are the result of being tortured and interrogated by enemy shinobi. The Land of Tea arc in the anime implies that some of his scars were pre-existing at the time of his encounter with Aoi.
- Gaara's "love" scar on his forehead happened when he attacked himself with his sand after an assassination attempt by his uncle.
- Kakashi has a scar over the eye he lost and replaced with a Sharingan. He received it saving Obito from an attack that would have likely killed him.
Rurouni Kenshin - The titular Manslayer's signature cross scar marks him as who he is and the incident that caused it made him decide to become a Technical Pacifist.
Fullmetal Alchemist has Sc ar who received his scar after His town was blown up by Kimblee. IIRC, Kimblee exploded the skin of his face in one or both versions.
Keroro Gunsou has Giroro's noticeable scar across his face, allegedly caused by Keroro
In Wolf's Rain, Tsume has an X-shaped scar on his chest. Toboe continually bothers him to know its origin, but Tsume doesn't actually explain until one of the last episodes in the series. It was a punishment from his former pack for his cowardice.
In One Piece, when talking to Whitebeard, Shanks points to the scars over his eye and uses it as an example of how dangerous Marshal D. 'Blackbeard' Teach really is, as he was the one who caused the wound.

Comic Books

Jonah Hex is horribly scarred. Typically, people tend to avoid asking how it happened but sometimes, there is the occasional person who is just too curious for his or her own good.

Bystander: Don't mean to pry, fella but how'd you get that scar?
Jonah Hex: Bit my cheek, eat'n.

Film

The page quote, taken from The Dark Knight, is one of several examples from the film.
In the live-action 101 Dalmatians, Jasper tells Horace that Skinner has a horrible scar on his neck from where a dog nearly tore his throat out, rendering him mute, and warns Horace not to ask him about it. Horace immediately forgets this warning upon seeing the scar, and Jasper decks him.
Jaws. Quint and Hooper show off their scars and explain how they received them. This leads to Quint telling the story of the USS Indianapolis.
Pay It Forward: Mr. Simonetti explains that his face was disfigured by his father freaking lighting him on fire.
In the Indiana Jones films, Indy has a small scar on his chin. At the beginning of Indiana Jones and the Last Crusade, we see a young Indy accidentally giving himself the scar the first time he uses a whip.
In the live-action Jonah Hex film, when asked about his disfigurement, Jonah explains: "Cut myself shavin'."
A tie-in storybook based on Disney's The Lion King actually explained how the villain got his scar in the first place. Go on. Guess the name of the bad guy!
In Treasure Planet, Jim asks Long John Silver how he became a Cyborg. Silver simply responds, "You give up a few things chasing a dream."
In Ice Age: Dawn of the Dinosaurs, Buck tells the story of how he lost his eye during his first encounter with Rudy.
In How to Train Your Dragon, Gobber regails the Viking kids with stories of how his leg and hand were eaten by dragons.
In RocknRolla, Those Two Russian Bad Guys are introduced talking about their various scars, which come from things like bullet wounds, grenades, barb wire, and even getting caught in tank tracks. One quickly gets the idea that they will be more than the misfit criminal protagonists have bargained for.
Chuck Norris in a Hong Kong action movie whose name escapes me. He's been arrested by the police who are listing his distinguishing marks for their report. In a clipped tone Chuck lists the cause of each scar as it's written down: gunshot, knife, pitchfork...
Shotgun Stories, a 2007 film starring Michael Shannon, is essentially named after this trope: Shannon's character has prominent scarring on his back from a shotgun blast, and several stories are told throughout the film, explaining them. Each story gives an alternate interpretation for who he is as a person, and for his motivations throughout the film.
In Chinatown, Jake's nose is slashed by a gangster. Similar to Jonah Hex above, his answer whenever someone asks is "Cut myself shaving."

Jokes

A pirate with a peg leg, a hook for a hand, and an eyepatch walks into a bar. The bartender asks him "What happened to your leg?" The pirate replies "That was the result of a fierce battle with a shark. I managed to fight him off, but he bit off my leg as a parting blow" The bartender then asks "Then what happened to your hand?" The pirate replies "I lost that in a swordfight. The dread pirate Blackbeard engaged me in combat, and he got in the last move." The bartender then asks "And your eye?" The pirate replies "That was due to a seagull. I was looking up and I saw him just before he pooped in my eye." The bartender asks "And that's what took out your eye?" The pirate replies "No, that's the first day I had my hook."

Literature

Captain Ahab in Moby Dick, who lost his leg while grappling with the Great White Whale.
Every member of the Seablite gang from Dark Life has a scar, all with the same story: they're surgical scars from Doc Hudson cutting them open to see how their Dark Gifts work.
Harry Potter has his famous lightning bolt, naturally, courtesy of You-Know-Who. There's also Mad-Eye Moody's scars from his career spent fighting Death Eaters, and Lupin's facial scars, self-inflicted due to his transformations. Averted with Dumbledore's scar on his kneecap shaped precisely like the London Underground; its mentioned offhand in the first chapter of the first book and then never explained or even referenced again.
Many characters in A Song of Ice and Fire bear scars, and probably the most notable "how-I-got-these" story would go to Sandor Clegane, who decides it would be fun to tell Sansa all about how his dear brother held his face down in a lit brazier when they were kids. Sansa is not enthused.
Callie, the protagonist of Cut by Patricia McCormick, has been sent to Sea Pines, a residential treatment facility, to deal with her Self-Harm problem. Callie mainly cuts herself on her arms, leaving scars that she tells the stories of to her therapist at one point in the book.
Dustfinger may be a subversion. The story behind his facial scars is humiliating rather than awesome: he was held down by a couple of thugs and carved up by a man who fancied his wife. He mentions several times that it was Basta who "decorated" his face, but it's someone else who actually explains what happened.

Live Action TV

A joke version occurs in Get Smart:

Hans Hunter: (re: his scar) Mr. Smart, have you ever heard of the Great White Rhino?
Maxwell Smart: That was done by the Great White Rhino?
Hunter: No, that was done by a small blue convertible.

In an episode of Blackadder, Redbeard Rum explains how he lost his legs.

Redbeard Rum: (to Edmund) I'll wager those legs have never been sliced clean off by a falling sail, and swept into the sea before your very eyes!
Edmund Blackadder: Well, neither have yours.
Rum: That's where you're wrong!

In the It's Always Sunny in Philadelphia episode "The Gang Buys a Boat," Mac decides to ask a sailor about his hook, thinking it will be a cool or interesting story.

Mac: So, how'd you loose that hand?
Sailor: Diabetes.

Thirty Rock: Liz Lemon questions her ex-boyfriend how he got his hooks. He explains that he got one of them when he was in Africa working for Doctors Without Borders, by waving at his old high school football coach from a helicopter ("It looked just like a black version of him!"). The second story is unexplained, but involves explosives.
The Jeffersons. Jennie is writing an article about gangs, and she starts to hang out with one. Each member has at least one scar, which they call "medals," and they are proud to show them to her and tell how they got them (in a knife fight, shot, etc.). One young trainee gang member doesn't have any medals yet but is looking forward to getting one in the next rumble - if he doesn't have a medal he can't become a full member of the gang. He ends up killed in the rumble.
In an episode of InSecurity, Burt and N'udu compare scars. The causes range from protecting the Ligerian ambassador from a Ganzi assassin's bullet to falling off a roof.
On Buffy the Vampire Slayer, Spike has a scar on his eyebrow, mainly because his actor James Marsters received one in a mugging. Still, in "Fool For Love", while Spike is telling flashback stories, one of them shows the character getting it by being sliced with a magical sword.
Averted in Merlin with Lancelot. When he shows up for the second time in the series he has a scar across his cheek, one that no one ever comments on. When he turns up a season later for the third time, the scar is completely gone.

Tabletop Games

In Traveller, Aslan never fix cosmetic damage (which does not inhibit performance) on warships. They consider it an honorable career to raise its value. This applies even if the ship was purchased from humans and earned its scars in a human navy.
In Werewolf: The Apocalypse, scars are a symbol of glory and honor. A good story can bring more renown if it's got a scar you can show off, and a wicked scar is always cooler if it's got a howl-worthy story behind it.

Newspaper Comics

In one Far Side strip, one sailor is telling another of how he got his peg leg. The other sailor, however, has a peg head.

Theatre

Henry V

This day is call'd the feast of Crispian.
He that outlives this day, and comes safe home,
Will stand a tip-toe when this day is nam'd,
And rouse him at the name of Crispian.
He that shall live this day, and see old age,
Will yearly on the vigil feast his neighbours,
And say 'To-morrow is Saint Crispian.'
Then will he strip his sleeve and show his scars,
And say 'These wounds I had on Crispian's day.'

Web Original

The story behind Weiss Schnee's surprisingly subtle facial scar is told in the White Trailer for RWBY.

Western Animation

Zuko's scar in Avatar: The Last Airbender came from when he spoke out of turn in a war council, protesting a plan involving sending a green regiment to their deaths for some tactical advantage, and his father the Firelord challenged him to a duel over it.

Firelord Ozai: You will learn respect, and suffering will be your teacher!

On The Simpsons, Bart asks the gun shop owner how he lost his arm. He replies, "You know how they tell you to keep your arms inside the bus?"
- In "Moms I'd Like to Forget", Bart goes to great lengths to learn the story behind a mysterious scar on his hand.
The Jaws example was spoofed in an episode of Eek! The Cat, where everyone is grossed out by Eek's scar (a paper cut).
In 'ThunderCats (2011), Panthro comments that there's "a lot of history" in the scars on his arms, which is the part he misses the most after sacrificing them to trap Grune inside the collapsing Astral Plane.