[[quoteright:320:http://static.tvtropes.org/pmwiki/pub/images/avengers_by_matt_4458.jpg]]
[[caption-width-right:320:Franchise/TheAvengers as explained by [[http://mattcantdraw.deviantart.com/gallery/35239567 Matt Cowan.]]]]

->''[[SpiderMan I got bitten by a radioactive bug]]\\
[[CaptainAmerica I tried an experimental drug]]\\
[[TheIncredibleHulk I went for a stroll on a gamma testing range]]\\
[[{{Thor}} I found an enchanted Uru cane]]\\
[[AntMan I made a serum that made me small\\
I modified the serum so it would make me tall]]\\
[[ComicBook/{{Daredevil}} I got a radioactive isotope in my eye]]\\
[[GreenLantern A dying alien helped me accessorize]]''
-->-- '''Ookla the Mok''', "Super Powers"

Every {{Superhero}} has an origin story, telling how they gained their powers and decided to fight crime. It may be revealed in their first appearance, or not until an eventual {{flashback}}, but once established it sets ground rules for which tropes are applicable to that particular {{Superhero}}.

The in-story explanation may be that the ultimate source of the hero's power is magic, {{Sufficiently Advanced Alien}}s, or WeirdScience. However, the actual origin tends to boil down to one of these:

* TheChosenOne (Given powers by an [[MentorArchetype ancient and wise being]], such as an [[TouchedByVorlons alien]], one of the PowersThatBe, or a being that's a [[SufficientlyAdvancedAlien combination of the two]]; e.g., Captain Marvel (who is [[IAmNotShazam not Shazam]]) or the SilverAge GreenLantern, or [[BequeathedPower the previous wielder handed it down]].)
* Non-Human Hero (They're superhuman because they're ''not'' human at all; e.g., aliens {{Superman}} or MartianManhunter; after all, they're [[SpaceIsMagic from space]].) They might alternately be [[GeneticEngineeringIsTheNewNuke genetically engineered]], a [[WeCanRebuildHim cyborg]] (inevitably involuntary and {{Angst}}ing over his [[WhatHaveIBecome condition]]), or otherwise a [[ArtificialHuman creation of science]]. In this case, expect them to be a PhlebotinumRebel.
* Lucky Accident (A FreakLabAccident, one-in-a-million malfunction, or what have you; e.g., [[Comicbook/SpiderMan Spider-Man]] or TheFlash.)
* My Own Creation (A scientist, engineer, or other makes-cool-stuff type invents something that gives them powers and uses it to help people; e.g., IronMan, Henry Pym (Ant Man/Giant Man/Yellowjacket/Goliath/Whatever he calls himself now). These types [[ReedRichardsIsUseless rarely sell their secret or use it to empower others]], usually on the basis of "I can't trust anyone else to use X responsibly".)
* Pure Will (A suitably motivated [[BadassNormal mere mortal]] achieves a high degree of competence in crimefighting owing to a combination of extreme training and/or scientific/engineering ability along with native ingenuity; e.g., Batman, the second (Ted Kord) BlueBeetle.)
* Random Selection (Something totally random that nevertheless isn't an "accident"; e.g., any [[{{Mutants}} mutant]] character.) Tends to be {{retcon}}ned into one of the others later.

...each of which has its associated tropes. Any of the last four may be {{retcon}}ned into The Chosen One. {{SuperVillain}}s also get their powers in these ways, though their accidents tend to be more unlucky. Occasionally, these can be compounded across several characters with a MassSuperEmpoweringEvent.

That's how they ''get'' their powers; motivations to actually fight crime include:

* TheCape
* SetRightWhatOnceWentWrong
* OrderVersusChaos
* ComesGreatResponsibility
* BoisterousBruiser
* BecauseDestinySaysSo
* LegacyCharacter
* ItsPersonal
* LaResistance
* LetsGetDangerous
* SmallNameBigEgo
* TheAtoner
* IJustWantToBeNormal (e.g. if a scientist wants to reverse his FreakLabAccident, or if the Chosen One has a task that's possible to complete.)
* ContrivedCoincidence

Often, the hero to be gets both powers and motivation in the same event, wrapped in one neat package. They may also get a supervillain arch-nemesis to fight, motivated and empowered by that same event.
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!!Examples

* Parodied in ''Webcomic/TheInexplicableAdventuresOfBob,'' when [[WeirdnessMagnet Bob]] ends up randomly stumbling through five different super hero origins in the space of a few minutes (alien ring, radioactive spider bite, cosmic rays, sadistic Canadian scientists, etc.), resulting in his becoming so powerful that he can barely move without destroying his surroundings.
* {{Captain Underpants}}'s origin story is told in [[ShowWithinAShow one of George and Harold's comics]] - he was born as "Little Baby Underpants" on the planet Underpantyworld, which was under attack by the Wedgie Warlords. Little Baby Underpants's father, Big Daddy Long Johns, created an amulet intended to prevent the planet's destruction from the spray starch the Warlords were using, but it ends up in his son's underwear. Big Daddy Long Johns and his wife, Princess Pantyhose, reluctantly decide to save Little Baby Underpants instead, and they slingshot him (using his underwear) to Earth, where he is adopted and renamed "Captain" by an old couple. Captain's birth parents eventually appeared to him in a dream, revealing his origins and inspiring him to become a superhero. Outside of the comics, Captain Underpants was created when George and Harold use a 3D Hypno Ring on their [[SadistTeacher mean principal]] Benny Krupp and can't properly undo the hypnotic trance as they lost the instructions. Resorting to breaking the trance by dumping water on his head, Krupp can be put back in the trance at the snap of a finger. He later gains superpowers as Captain Underpants when given superpower juice, though wearing clothes as Mr. Krupp keeps these powers dormant.
* DCComics' ComicBook/AmbushBug claims that his costume was sent to Earth by a scientist who predicted (wrongly) that his planet would explode; along the way the clothes were bitten by a giant space radioactive spider. Obviously, this is a send-up of both {{Superman}}'s and {{Spider-Man}}'s origins. Considering Ambush Bug is crazy, he likely made up the whole thing.
* In the book ''Superpowers'' the character telling the story directly refuses to explain what happened to give the students their powers. Partly this is to keep the information out of the wrong hands, but mostly it's to avoid an avalanche of snide letters telling him his science is all wrong.
* Played with in ''[[Webcomic/M9Girls M9 Girls!]]'': The Girls get terminally ill after their FreakLabAccident. Of course, their mentor immediately proceeds to cure them with LEGOGenetics.
* In ''[[http://johnnysaturn.com Johnny Saturn]]'', most of the superheroes (called ''[[DifferentlyPoweredIndividual metaheroes]]'') are modern versions of Greek gods. Many of the metaheroes have descended from higher dimensions, or are alien hybrids, or non-powered ''mystery men,'' such as Johnny Saturn himself.
* {{Deconstructed}} by the post-Crisis CaptainAtom, whose actual origin was kept secret by the military, which "revealed" his pre-Crisis, SilverAge, Charlton comics origin as his origin to the public.
* A running joke in Ed Brubaker's ''ComicBook/{{Sleeper}}'' is that bored supervillains like to kill time by telling third-person, slightly hokey versions of their own origin stories. These are accompanied in the story by an ArtShift to brighter colors and a more traditional panel lay-out.
* CiemWebcomicSeries. Stan Flippo was experimented on by aliens, who fused his genes with those of a mutated centipede. His ''[[LamarckWasRight daughter]]'' gets superpowers.
* In CityOfHeroes, the above 5 origins are organized thusly: Magic, Kheldian/Natural, Science, Technology/Natural[[labelnote:*]]Natural can be "[[BadassNormal you're just that tough]]" OR "this is normal for your species"[[/labelnote]], and Mutant.
* Elliot of ''Webcomic/ElGoonishShive'' [[http://wiki.rpg.net/index.php/File:MPost20657-e22115fa0c_o.jpg reminds]] why most try keep their origin secret.
* In ''Series/BuffyTheVampireSlayer'' Buffy is explicitely referred to as TheChosenOne (though, even when we finally get told how Vampire Slayers came to be, who or what does the choosing is still left vague) and fights evil mainly BecauseDestinySaysSo and, with great ass-kicking ability, ComesGreatResponsibility.
* ''Series/{{Angel}}'', meanwhile, had its main character be of non-human stock (namely, a vampire) who fights other demons because he's TheAtoner who, if he plays the right role in the coming apocalypse, might [[IJustWantToBeNormal get to become human again]].
* Jack Hawksmoor of {{The Authority}} has a particularly odd origin: He was repeatedly abducted and altered by what he thought were aliens, who were in fact [[spoiler:time-travellers from the 70th century, in order to use him as a weapon to fight a rampaging Kansas City by bonding with Tokyo]]. ...yeah.
* "One day, at the scene of a fire, the cop found the perfect fireman axe. That was the day he became... ''Webcomic/AxeCop''." Yes, that's his whole origin.
* Interestingly, both Metro Man (a {{Superman}} {{Expy}}) and his arch-nemesis WesternAnimation/{{Megamind}} have the same initial origin mirroring Superman's - they're both from neighboring planets that were sucked into a UnrealisticBlackHole. The difference is, Metro Man looks human but has Superman's powers. Megamind has a large cranium, is completely blue, and is devilishly smart (he can also survive a MegatonPunch but otherwise has no powers). Also, while Metro Man was raised by loving, rich parents, Megamind was raised by convicts in prison.
* DC, at one point, had a lot of heroes with the "lucky accident" origins whose accidents had been rendered laughable as [[ScienceMarchesOn science marched on]]. To reconcile this, they introduced the concept of a "metagene", a dormant gene carried by all these characters that activated in the presence of these accidents that would have crippled or killed any other person who lacked the gene, thus transforming their "lucky accident" heroes into "random selection" heroes.
* Parodied in ''[[PhilFoglio What's New? with Phil and Dixie]]'', in which a single hero-to-be is subjected to so many variants of this trope that he's [[DeathByOriginStory reduced to ashes]] by their cumulative effects.
* Deconstructed in ''Film/BatmanBegins'': [[{{Mooks}} Mook]] Joe Chill kills Bruce Waynes parents. BadCopIncompetentCop Gotham police cannot deliver justice to him. TheMafia Don Carmine Falcone gives Bruce Wayne a TheReasonYouSuckSpeech that forces him to begin TheHerosJourney, then he is trained by the [[MurderInc League of Assasins]] and outsmarts CorruptCorporateExecutive Earl to become Franchise/{{Batman}}. A possible explanation is that Gotham was a CorneredRattlesnake and it is trying to produce a superhero to survive: Notice that all of the forces oppressing Gotham were {{ThresholdGuardian}}s that created the {{Superhero}} that will fight them.
* An odd retroactive example in the Literature/{{Leviathan}} trilogy by ScottWesterfeld turns the ''entire'' trilogy into one for a couple characters due to the ending. [[spoiler: The main characters Deryn and Alek make a career change from, respectively, a bio-zeppelin midshipman and Prince-in-exile to agents under the employ of the powerful Zoological Society. Some cryptic remarks in conjunction with the skills they learned throughout the trilogy and the experiences they've had would seem to suggest that they were recruited to be international espionage or diplomatic agents of some sort. However, we're never actually shown what the Zoological Society has planned and the trilogy is done at that point. Whatever the case, after the trilogy they are set up to become powerful and professional figures in the field of political intrigue, whereas they were competent but ragtag amateurs working off limited resources during the trilogy.]]
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