[[foldercontrol]]

[[folder: ''Manga/Bleach'' ]]

* In ''FanFic/HogyokuExMachina'', Yoruichi is surprised when she finds out that the Vizards fought alongside Soul Society against [[BigBad Aizen]] in the [[TimeTravel original timeline]], since they have no reason to like them. [[TheSmartGuy Ishida]] suggests it was because of this trope.

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[[folder: ''Comic Strip/Calvin And Hobbes'' ]]

* [[CardCarryingVillain Dr. Brainstorm]] tries to {{def|iedTrope}}y this twice in ''Fanfic/CalvinAndHobbesTheSeries''. Both times, he ends up playing it straight.

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[[folder: ''Western Animation/Chip N Dale Rescue Rangers'' ]]

* ''[[Fanfic/TheNowakverse Under the Bridge]]'': Widget has taken several attempts at killing Gadget. Now Chip calls her on her submarine ''Albacore'' on the radio, alerting her that Gadget is out to attack and sink ''Albacore'' with a self-made, air-dropped torpedo. But the call comes in time: A young squirrel from Widget's crew named Andy injured an ankle on an unprotected chain, and now Widget needs Gadget and her aircraft to take him to a hospital. Meanwhile, when Widget comforts Andy, this also helps trigger her HeelFaceTurn.

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[[folder: ''Literature/Chronicles Of Narnia'' ]]

* In ''FanFic/{{Carpetbaggers}}'', when the newly-crowned Pevensies need backup to fight a horde of the Witch’s creatures, they recruit the rebels who were holed up in the castle bullying and blackmailing local Narnians.

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[[folder: Cross Over ]]

* In ''FanFic/AeonNatumEngel'', during the Herald fight, the Migou recall some of their forces so that the NEG Military, with the newly freed-up forces, can assist in defeating the Herald. Humanity doesn't return the favor.
* This happens in the Naruto/Justice League crossover ''Fanfic/ConnectingTheDots'' when Naruto and Sasuke team up against a REALLY big threat.
* ''FanFic/BurningBlack'': Anti-Cosmo, and by proxy every anti-fairy he commands, allies with Team Turner against Remy and [[spoiler:[[TheManBehindTheMan the Pixies]]]] in Act 3. He even outlaws the use of bad luck on Timothy directly; indirect bad luck is still fair game. The relationship is creeping into FriendlyEnemy territory, which makes Cosmo and Wanda very nervous as Timmy's exposure to anti-fairies affects his personality and allows him to use black magic while giving him immunity to anti-magic waves.
* ''FanFic/ADarkKnightOverSinCity'' features Franchise/{{Batman}} and the [[AntiHero anti-heroes]] from SinCity teaming up together and with other criminals in order to achieve their goals.
* ''FanFic/AShadowOfTheTitans'': Jinx briefly teams up with the Titans after Mumbo captures both Jade and Starfire and forces them to be his "assistants". Jinx describes it as "sharing a mutual problem", and as soon as Mumbo is defeated she grabs Jade and runs off.
** The possible BadFuture glimpsed in the "[[MindScrew Destiny]]" interlude has another apparent example: [[spoiler: whatever "[[NamesToRunAwayFromReallyFast Omega]]" is, it's so bad that the Demon Sorcerers and the Eight Immortals team up with each other and [[FutureBadass Good!Jade]] to stop [[FutureMeScaresMe Evil!Jade]] from releasing it.]]
** Jade and Raven teaming up against the Master of Games.

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[[folder: ''Manga/Death Note'' ]]

* In the CrackFic ''Fanfic/AllYouNeedIsLove'' Light seeks help from L and Naomi Misora after [[HilarityEnsues "misplacing" a Death Note.]]
* In ''FanFic/ACureForLove'' [[ArchEnemy Light/Kira considers L]] to be his "partner" in destroying the [[WesternTerrorists Astraea Organization]] [[spoiler: [[HijackedByGanon at first, before he usurps control of their organization]]]].

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[[folder: ''Franchise/Halo'' ]]

* ''FanFic/EnemyOfMyEnemy'': ExactlyWhatItSaysOnTheTin, and awesome. Take a UNSC colony and add one shipload of Elites being chased by one carrier full of Brutes...

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[[folder: ''Western Animation/Invader Zim'' ]]

* ''FanFic/MyHostageNotYours'': Zim originally helping out Gaz (and Dib by extension) is this trope, before [[RelationshipUpgrade evolving]].
** Tak teams up with Dib's [[LaResistance Group]] in the third story just for revenge against Zim. [[spoiler: When they defect from the Swollen Eyeballs, they team up with Zim and Gaz to defeat them.]]

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[[folder: ''Western Animation/Jackie Chan Adventures'' ]]

* ''FanFic/QueenOfAllOni'': When Valmont uses the power of Kaito's mask to steal the Ninja tribe away from Jade, she and Jackie briefly (and reluctantly, in her case) team up to defeat him.
** Subverted in one of the scenes set in [[GhostInTheMachine Jade's mindscape]] -- Hero tries to form an alliance against [[SuperpoweredEvilSide The Queen]] with his apparent rival Father, but is rejected.
** In a similar subversion, the J-Team refuses to ally with [[FutureBadass Karasu]] against Drago, as they don't see any good coming from working with a Shadowkhan.

[[/folder]]

[[folder: ''Western Animation/My Little Pony Friendship Is Magic'' ]]

* ''FanFic/ABriefHistoryOfEquestria'': When Wind Whistler led a coup against [[TheCaligula Commander Sullamander]], she recruited help from Star-Swirl the Bearded and the few unicorns loyal to him. True, Star-Swirl was open-minded and friendly with the other tribes, but that's still members of one nation asking help from members of a rival nation to overthrow their leader.
* ''FanFic/TheImmortalGame'': In a plan [[GodzillaThreshold born of desperation]] to defeat [[BigBad Titan]] during the FinalBattle, the Mane Six end up allying with [[spoiler: Discord]]. As [[spoiler: Celestia]] puts it, they know the latter will probably betray them after they're done with Titan, but they can handle that, and besides, "[[LesserOfTwoEvils better the devil you know]]".
* ''FanFic/ThePowersOfHarmony'': After she [[spoiler: [[DemonicPossession possesses her]]]], [[TheDragon Eclipse]] is able to convince Rarity to help her [[TheStarscream plot against]] [[BigBad Cetus]], and together they plan to bring Twilight into the fold as well. Or at least, [[GuileHero that's what Rarity wants Eclipse to think]].
** Played straight when the Changeling Princess Pupa allies with Applejack's group to stop (her sister) Chrysalis' invasion of Gildesdale, with the promise that afterwards she'll also ally her people with the ponies against Cetus.
* At the climax of ''[[FanFic/PoniesOfOlympus Rolling in Beaches]]'', Spike convinces the hippocampi and Scaly Back River Clan dragons to put aside their differences in order to stop all the dragons [[spoiler: and Mane Six]] turned into monsters by [[TheCorruption the Rainbow of Darkness]].
* In the ''FanFic/PonyPOVSeries'', the backstory for the [[BadFuture Dark World]] has this happening twice between [[EvilOverlord Discord]] and the various LaResistance groups arrayed against him (primarily the [[HeelRaceTurn Changelings]]) -- first during the [[AlienInvasion invasion]] by the [[TabletopGame/{{Warhammer40000}} Imperium of Man]], then centuries later during his [[EvilVersusEvil war with Grogar]] (in both cases, Discord was viewed as the LesserOfTwoEvils).
** Clover's story in the ''7 Dreams/Nightmares'' collection reveals that eons ago, a group of {{Eldritch Abomination}}s escaped the loss of their own reality by entering the POV [[TheMultiverse multiverse]] with the intention of absorbing all beings into their HiveMind in order to torment them for all eternity. This offended ''both'' [[TopGod Fauna Luster and Entropy]] -- the former because She's a strong believer in free will, and the latter because it would potentially prevent the end of all things She [[OmnicidalManiac embodies and desires]] -- leading to Them, Their Mates, and Their respective children working together to defeat these things and [[SealedEvilInACan seal them]] beyond the Gates of Tartarus. It's noted in-universe that this is the ''only'' time the two of Them have ''ever'' agreed on ''anything''.
** During the Wedding Arc, while they're unaware of it, the heroes' efforts are being aided from the sidelines by [[spoiler: Discord and Nightmare Diamond]], who are aware that if Chrysalis succeeds in her plans, she'll be [[AGodAmI powerful enough]] to be a threat even to them.
* In ''FanFic/TheConversionBureauColdWar'' the United States of America and the Soviet Union put aside all differences to fight a xenocidal race of Ponies.

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[[folder: ''Manga/Naruto'' ]]

* ''[[http://www.fanfiction.net/s/6585953/1/Boutoku-no-Naruto Boutoku no Naruto]]'' has Kyuubi willing to help Naruto out of hatred for the shinigami. When [[ForWantOfANail Naruto learned Edo Tensai instead of Kage Bunshin]], Kyuubi offered him a deal.
-->'''Kyuubi''': "Because I hate. There are many things I hate. The Sage of the Six Paths. Madara Uchiha. Hashirama Senju. Mito Uzumaki. Minato Namikaze. The toads. Kushina Uzumaki. But more than anything else, I hate the Shinigami. He stole over two thirds of my power, and claimed the Namikize's soul in return, a violation of his own laws and rights. The Shiki Fuin, the contract with the Shinigami, works on a simple basis. A soul for a soul. He did not take my soul, merely my power. When I was sealed, he had nothing to do with it. By the ancient laws, he should have let the Namikaze go, or at least send him to the Pure World, and return my power to me. But he didn't, breaking ancient law. ... You see, he has stolen from me, so I will ensure that he suffers for it! You Naruto, are the key of my vengeance. Through you I will make him suffer. All I ask is that you call back many, many souls, I don't even care for what, and in return, I will give you what all other jinchuuriki can only dream of, my full support."

[[/folder]]

[[folder: Real Person Fic ]]

* Villain example: Although [[spoiler: Brox and Co.]] and the Raleka in ''Fanfic/WithStringsAttached'' aren't exactly mortal enemies, they dislike each other considerably. [[spoiler: Brox and Co.]] are contemptuous of Ketafans in general, and the Raleka hate that the skahs want to use the sacred Vasyn for stupid purposes. However, they work together against the four because the Raleka cannot do certain things without [[spoiler: Brox's help]]. We find out later that [[spoiler: Brox and Co.]] were planning to betray the Raleka, but Paul and George inadvertently screwed this up for them.

[[/folder]]

[[folder: ''Franchise/Spider Man'' ]]

* One issue of ''[[FanFic/UltimateSpiderWoman Ultimate Spider-Woman: Change With the Light]]'' has petty criminal Blizzard teaming up with Spider-Woman to help her protect the innocent people in danger during an invasion of New York City by an army of BrainwashedAndCrazy super villains. Taking inspiration from the ''WesternAnimation/DarkwingDuck'' episode where DW teamed up with Megavolt (see below), Blizzard points out that if New York is destroyed, there'll be nothing left for him to rob.

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[[folder: ''Franchise/Star Trek'' ]]

* ''Fanfic/RealityIsFluid'': Eleya is able to convince an Undine commander that the Federation et al. were ''not'' responsible for the attacks on Undine spawning pools and hatchlings that sparked the current war, and that faction begins targeting the Undine that have been infiltrating the Alpha and Beta Quadrant powers ''and'' agrees to join the fight against the [[BigBad Iconians]] when the time comes.
* In the fic ''[[https://www.fanfiction.net/s/9694363/1/Safe-and-Sound Safe and Sound]]'', Kirk and Khan pull one of these, similar to the one they pulled in the [[StarTrekIntoDarkness second film]], in order to save the [[spoiler: kidnapped Nyota Uhura, Joanna [=McCoy=] and Lucille Harewood. This time, Khan doesn't betray him]].

[[/folder]]

[[folder: ''Franchise/Tolkiens Legendarium'' ]]

* In ''FanFic/AFarGreenCountry'', Durus and Surad were enemies of Elden and Nellas, but these four quickly become allies when they are chasing a common enemy.

[[/folder]]

[[folder: ''Transformers'' ]]

* In the Transformers fanfic ''[[Fanfic/AChildShallLeadThem A Child Shall Lead Them]]'', the Dinobots end up teaming up with Galvatron and Cyclonus to escape the Quintessons. Galvatron ends this alliance fairly quickly when he literally stabs Pterodactus Prime (aka Swoop) in the back.

[[/folder]]

[[folder: ''Literature/Worldwar'' ]]

* ''FanFic/WorldwarWarOfEquals'': In light of the pending threat of invasion by the Race, various nations around the world put aside their differences to form mutual defense pacts:
** Egypt and Israel set aside differences and set up a military alliance with Turkey before The Race arrives.
** Colombia and Venezuela, who were waging a war just months before the Race's arrival, agree to a cease fire and start preparing for the incoming invasion.
** Every drug cartel in Ciudad Juarez fights alongside the Mexican military in the city against Race forces.

[[/folder]]

[[folder: ''Literature/Worm'' ]]

* In FanFic/{{Cenotaph}} [[CivilianVillain Purity]] and [[GuileHero Skitter]] team up to fight the ABB. On one hand a flying Blaster, [[TheAtoner ex-Nazi]] single mother. On the other, a ruthlessly intelligent, highly resourcefull teenage highschool student and [[spoiler: newly-minted orphan]] with dreams of being a hero. Together, they fight crime!

[[/folder]]

[[folder: ''Series/The X Files'' ]]

* The example from WildMassGuessing for ''WMG/TheXFiles'', suggesting that as soon as the aliens arrive on Earth, they'll promptly be beaten back by ''every single MonsterOfTheWeek'', who tend to favor continuing to live on their planet.