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[[quoteright:349:[[Literature/WorldWar http://static.tvtropes.org/pmwiki/pub/images/eggletonworldwar.png]]]]
[[caption-width-right:349:What if aliens invaded during UsefulNotes/WorldWarII?]]
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->''"1865 -- Alien bats from outer space bring the fruits of their technology to their brothers, because they have heard Music/ElvisPresley on the radio, and think that the south should indeed be free. It ranks slightly higher than a '63 CSA victory. Indeed, I think I will call it "Bats of the South", and make it into a four book trilogy."''
-->-- '''Alison Brooks''', discussing the probability of various AlternateHistory Confederate victories in UsefulNotes/TheAmericanCivilWar on [=soc.history.what-if=]

An AlternateHistory trope dealing with the divergence of a timeline. If the point of divergence is an extraordinary or supernatural phenomenon, Alien Space Bats are responsible.

The phrase was originally coined by the late Alison Brooks as a sarcastic comment on ridiculous alternate history timelines with no realistic chance of happening without some sort of DeusExMachina as implausibly contrived as bringing in a bunch of SufficientlyAdvancedAlien bats. It was only later that it came to mean "explicitly magical or science-fiction what-ifs."

Alien Space Bats are in a sense the opposite of a DeusExMachina: where DeusExMachina is the introduction of an implausible element outside of the context of the narrative to ''resolve'' a plot conflict, Alien Space Bats are an implausible element outside the context of the narrative introduced in order to ''set up'' the main plot conflict or setting.

The trope may also apply when the point of divergence isn't actually supernatural, but is so wildly implausible that it might as well be that AWizardDidIt.

Note that [[TropesAreTools Tropes Are Not Bad]]: this can and does lead to some excellent yarns, especially if SchizoTech is involved. Even if the event setting up the plot is fantastic or wildly improbable, [[IntendedAudienceReaction that doesn't mean that the character's reactions to it have to be equally unrealistic]]. However, people who use alternate history to explore the nature of real historical processes may regard Alien Space Bat stories as annoying distractions, or at least as trivial mind games.

A frequent mechanism by which Alien Space Bats intervene in human history is MassTeleportation.[[note]]Sometimes colloquially referred to as an "ISOT" after S.M. Stirling's novel ''Literature/IslandInTheSeaOfTime''.[[/note]] When on a small scale, their intervention may leave people TrappedInThePast. See also NeverWasThisUniverse.

Not to be confused with GoddamnBats, or the Franchise/{{Batman}} from ''SpeedingBullets,'' who actually ''is'' an alien. Only vaguely related to the movie ''{{Film/Lifeforce}}'', which is not AH, but has ''literal'' alien bats.

[[http://en.wikipedia.org/wiki/Alien_space_bats Now a verifiable wiki article]]! That cites this very page on [[Wiki/TVTropes This Very Wiki]]!



[[folder: Anime and Manga]]
* ''Manga/{{Zipang}}'' diverges from history in the wake of the Battle of Midway when a modern Japanese Aegis destroyer is sent back to 1942 by a NegativeSpaceWedgie.
%% Code Geass is not this trope. It's Never Was This Universe--there are far too many points where the timeline diverges from ours. Commented in order to keep people from trying to re-add Code Geass as an example here, and Code Geass is already an example on the Never Was This Universe trope.
* The world of the 2003 anime ''Anime/FullmetalAlchemist'' diverged from the normal world when alchemy was discovered. Conversely, the world of the manga NeverWasThisUniverse.
* Interestingly enough in ''Manga/BillyBat'', [[spoiler: the titular character, a ''literal'' Alien Space Bat, intends to prevent or avoid his world from diverging from our history when it's within his power.]]

[[folder: Comic Books]]
* ''Comicbook/{{Watchmen}}'': The exact point of divergence seems to be the presence of "costumed heroes", which isn't ''too'' fantastic ([[BadassNormal none of them have any superpowers]]), but most of the really major differences can be attributed to [[PhysicalGod Dr. Manhattan]], whose appearance marks the point where the course of global politics and history dramatically shift, like the US winning UsefulNotes/TheVietnamWar, or the Soviet invasion of Afghanistan put on hold. [[InSpiteOfANail For a while.]]
* ''ComicBook/{{Marvel 1602}}'' has everything fairly normal up until the future Franchise/MarvelUniverse suddenly imposes itself on the past.
* One alternative world ComicBook/TheAuthority fought diverged when blue-skinned aliens arrived in Italy during the Renaissance.
* In the Franchise/MarvelUniverse, [[ComicBook/BlackPanther Wakanda]] is one such example. Thanks to a meteor of {{Unobtainium}}, the Wakandan people developed advanced technology early, and thus were never colonized by European nations.
* The crashed alien spaceship in {{Comicbook/Miracleman}}.
* ''ComicBook/{{Uber}}'': Shortly before the Fall of Berlin, the Nazis develop superpeople using alien technology. Subsequent developments, in a deconstruction of StupidJetpackHitler, are carefully thought through and extremely depressing.
* ''ComicBook/PaxRomana'': When time-travel is discovered in the near-ish future, an ailing Catholic church sends a paramilitary force with modern weaponry and vehicles, as well as three weather-spy satellites and half a dozen nukes, to 312 CE to prop up Rome and the foundations of the church. Things don't go precisely to plan, but the ending shows that humanity has space colonies in the 15th century.

[[folder: Film]]
* ''Film/TheFinalCountdown'' and a few imitators also have some sort of NegativeSpaceWedgie toss an individual, a country, or a military force back or forward in time so they can change history. The film was a StableTimeLoop. Imitators, however, may not include this aspect.
* Possibly referenced in ''WesternAnimation/JusticeLeagueCrisisOnTwoEarths''; when Superwoman is trying to decide which alternate Earth to send Batman to, she glosses over one where humanity has "mutated into hideous winged creatures of the night".

[[folder: Literature]]
* The ''Literature/SixteenThirtyTwo'' series has a small modern American town physically relocated to 17th-century Germany by some process that the author discusses no further than to vaguely say that advanced physics could probably explain it. It does give a tiny bit of exposition about the Space Bats in question (The temporal anomalies are the result of a StarfishAlien creating multi-dimensional art, and compared to shards chipped away from a stone to make a statue), and notes that eventually, they get their just desserts at our descendants' hands for the general hazard their art poses, but that's all in the prologue, after which they never appear again. Creator/EricFlint, the author, explicitly said that he created the Bats in question to allow him to write as many AlternateHistory novels as he liked.
* John Birmingham's ''Literature/AxisOfTime'' trilogy, inspired by ''Film/TheFinalCountdown'' (see above), depicts a military task force that gets sent [[TimeTravel back in time]] from 2021 to 1942 as a result of a failed experiment on one of the ships in the task force.
* ''Without Warning'' and its sequel ''After America'', also by John Birmingham, set in 2003 and after, feature a wave of unknown energy that causes the population of most of North America to be suddenly disintegrated. Other, non-primate animals are either unaffected or destroyed on a seemingly random basis.
* In Creator/HarryTurtledove's ''Literature/TheGunsOfTheSouth'', the Confederate States win UsefulNotes/TheAmericanCivilWar because time-traveling South Africans give them AK-47s.
** ''Ravage'' uses an identical premise, but falls under the category of future rather than AlternateHistory, as it takes place in the 21st century and was written in 1943.
* The (nowadays less-known) likely progenitor of the "CSA victory" variation of AlternateHistory, ''Literature/BringTheJubilee'' by Ward Moore, [[PlayingWithATrope utilizes the trope with a twist.]] The basic premise is a classic example: history is changed by a time traveller affecting [[ForWantOfANail one small event]] (accidentally, in this case). The twist is that [[spoiler: in-universe, the historical reality ''was'' a Confederate victory (for wholly mundane and plausible reasons). The time-travel experiment and its consequences aren't shown until near the end of the novel, and the result is the emergence of an alternate timeline in which the USA won—i.e., ''our'' world is the AlternateUniverse from the novel's perspective.]]
* The ''Literature/BelisariusSeries'' is a good example; its divergence is the result of a TerminatorTwosome of warring [=AIs=] [-FROM THE FUTURE-]. Link was sent by a group of MasterRace-type purists to prevent a future full of what they see as TranshumanTreachery, while Aide was sent by kind, gentle TranshumanAliens (of the SpaceWhale persuasion) Link is trying to RetGone.
* The major point of divergence in the ''Literature/WildCards'' franchise is the outbreak of the eponymous virus on Earth, which bestows superpowers on its victims (that is, if you can avoid the [[SuperpowerRussianRoulette horrible death part]]).
* In an intentional {{homage}} to this trope, Creator/{{Ken MacLeod}}'s ''Learning the World'' is set on a planet inhabited by actual Alien Space Bats -- to whom humans are the mysterious alien visitors who change the course of history.
* Ben Jeapes' children's novel ''The New World Order'' diverges in the middle of the UsefulNotes/EnglishCivilWar when Neanderthals from a parallel universe invade and steamroll over both sides with roughly UsefulNotes/WorldWarI level technology. Also they have a few wizards.
* Creator/KimNewman's ''Literature/AnnoDracula'' has {{Dracula}} as ruler of UsefulNotes/TheBritishEmpire instead of Queen Victoria. (Officially, alongside Victoria, having ascended the throne as her prince consort, but it's made clear that he has taken all the power.) This leads to other vampires coming out of the coffin and becoming an open part of society, with the sequels exploring how the consequences unfold in the following century.
* Creator/NeilGaiman's ''Literature/AStudyInEmerald'' has Creator/HPLovecraft's [[EldritchAbomination Old Ones]] as rulers of UsefulNotes/TheBritishEmpire instead of Queen Victoria.
* Creator/SMStirling is noted for this trope, probably because he was a regular reader of the newsgroup where the term was coined:
** ''Literature/TheDraka'' has the initial divergence of American and French royalists being sent to the fictional colony of Drakia. It then has a number of others, such as the existence of an incredibly complete cache of classical literature in Western Africa, and the spontaneous appearance of several technological advances in a culture with little incentive to have them. For example, they send steam-powered warcars to help the Confederacy, and have enough dirigibles to launch an air raid that kills 50,000 people against Russia in the 1880s. They also have atomic bombs by 1944, but so does the United States.
** ''Literature/IslandInTheSeaOfTime'' starts with the Event: Alien Space Bats sending Nantucket (and a big ellipse of ocean surrounding the island) [[TimeTravel back in time]] to the Bronze Age.
** The ''Literature/{{Emberverse}}'' novels: in the 1998 from which Nantucket was taken, the same Alien Space Bats cause all industrial-level technology to become useless. {{Lampshade|Hanging}}d as some of the characters explicitly use the term "Alien Space Bats" as a label for whatever unknown force caused most human technology to suddenly stop working.
** In ''The Sword of the Lady'', these particular Bats are revealed to be [[spoiler: the ''Mind'', essentially the Jungian Universal Subconscious having an argument with itself]].
** ''Literature/TheLordsOfCreation'' series is set in an alternate history where Mars and Venus are habitable (having been made so centuries ago by the eponymous advanced alien race, for reasons not yet revealed).
* Creator/HarryTurtledove's ''Literature/WorldWar[=/=]Colonisation'' books - the point of divergence is aliens invading during UsefulNotes/WorldWarII.
* In the Creator/RogerZelazny book ''Literature/{{Roadmarks}}'', the [[TimeTravel time-traveling]] main character keeps attempting this to fix Thermopylae (in the story the Greeks lost) but the TimePolice keep catching him.
* In ''Literature/TheChroniclesOfAmber'' by the same author, the characters' primary power comes from being space bats themselves. They tend to drop into timelines, fiddle around with them, and then use the resulting alternate-history worlds as a source of labor and material later. Corwin spends a couple of books using this to [[spoiler:set up an invasion of the main world/timeline by a 'nearby' one that worships him as a god, with material from a second alternate timeline that functions as gunpowder in the main timeline, which didn't itself have guns yet]].
* Elizabeth Bear's '' [[Literature/NewAmsterdamBooks New Amsterdam]]'' has alien space bats in the form of magic warcraft used by Native Americans, preventing Europeans from settling the Americas except spottily along the coasts.
* ''Thor Meets Captain America'' by Creator/DavidBrin has Nazi Germany essentially winning World War II because they were able to summon the Norse gods to fight on their side. [[spoiler:They ultimately lose it all when Loki -- whose titles include "The Ever-Contrary" -- betrays them.]] The trope was used to make a point here: this was the ''most plausible scenario'' the author could think of that would have the Nazis winning.
* Steven White's ''Saint Antony's Fire'' starts off with Ponce de Leon discovering the wreck of an interdimensional UFO, quickly followed by the resurrected aliens allowing the Spanish Armada to successfully invade England.
* Naomi Novik's ''Literature/{{Temeraire}}'' series is set in the Napoleonic Wars in a universe where ''dragons'' exist and are widely used by humans, especially militaries. The AlternateHistory elements are [[InSpiteOfANail not immediately apparent]], but there are numerous key differences; the Incans, for instance, are a major world power because of their dragons, and the Chinese, far from being in decline and getting bullied by Western powers, are one of the major players in the war as both sides try to enlist their aid, or at the very least keep them from joining the other side.
* Taylor Anderson's ''Literature/{{Destroyermen}}'' series has the Squall, a bizarre, recurring storm that has repeatedly transferred ships from our Earth to an alternate timeline where the K-T extinction event did not occur.
* In John Birmingham's ''Without Warning'', just before the 2nd Gulf War, a strange energy bubble appears over North America and kills all primate life within it's premises. One of the consequences is Israel nuking the Middle East and New York City being attacked by pirates (many of them being refugees from the Middle East).
* In the third book of ''Literature/TheDireSaga'', it's revealed that this world's alternate history with worldwide broadcast power, artificial and digital intelligences, and superpowers is the result of UsefulNotes/NikolaTesla's Wardenclyffe Tower experiments ending a bit differently than in our timeline. He gained lightning powers, other people started gaining superpowers, and people suddenly popped up who claimed to have always known magic. One of Tesla's contemporaries muses that they may have accidentally transported themselves to another universe.
* Donald R. Bensen's novel ''And Having Writ...'' begins with the crash-landing of four alien explorers (with the implication that in the real timeline, their craft [[TheTunguskaEvent exploded over Siberia]]) in 1908. The aliens attempt to manipulate world powers into a war to spur technological progress so they can get home; ironically, their actions spur technological progress while ''averting'' UsefulNotes/WorldWarI.
* Deconstructed in Lavie Tidhar's novel ''The Violent Century'', in which WWII [[StupidJetpackHitler involves superpeople]] due to a MassSuperEmpoweringEvent during the inter-war years, but historical forces are sufficiently powerful that the broad outline of twentieth-century history doesn't change at all. In a darkly humorous twist, some of the characters end up convinced that they must be in a dark AlternateTimeline and that history without superpeople couldn't possibly have gone so horribly wrong.
* The classic ''Literature/LestDarknessFall'' by Sprague deCamp: some mysterious process that's never fully explained transports a present-day (i.e., 1930s) archeologist to fourth-century Rome.
* ''Literature/WithoutWarning'' offers one in a more recent past. A mysterious energy bubble called the Wave engulfs most of North America, killing all within and denying entry, on the eve of the 2003 invasion of Iraq. The trilogy examines the consequences of a modern world without America, as well as the struggles to survive and rebuild.

[[folder: Live-Action TV]]
* A few ''Series/{{Sliders}}'' episodes fell into this, with worlds where physical laws permitted magic and wizardry and dragons, whereas other worlds were ForWantOfANail. Still other worlds the Sliders visited combined these aspects. Interestingly, only one world had an event that fits the "alien" bit. According to the show, all those alien conspiracies on other worlds are actually true. The only difference on this world is that the government went public with FirstContact and established open trade with the Reticulans, resulting in many technological advances (including a virtual panacea, anti-gravity, and a manned mission to Mars). Disappointingly, the characters themselves don't actually get to meet any aliens. The best they get is a human who looks part-Reticulan thanks to a side effect of the panacea drug (his blood is also green).

[[folder: Tabletop Games]]
* The TabletopGame/{{GURPS}} ''TabletopGame/InfiniteWorlds'' campaign has two major opposed alternate-reality-jumping factions (Homeline, our world circa 2027 if [[AppliedPhlebotinum paratemporal technology]] had been invented in 1994, and Centrum, a recovered post-apocalyptic OneWorldOrder of {{Straw Vulcan}}s with similar tech) often act as this in other timelines to further their own interests (which right now is mostly screwing up the rival faction). The players are probably going to work for one or the other.
* In ''TabletopGame/{{Shadowrun}}'', TheMagicComesBack on MayanDoomsday.
* ''TabletopGame/{{Deadlands}}: The Weird West'' starts with a vindictive Native American shaman unleashing SealedEvilInACan, which leads to all sorts of weirdness, like the Battle of Gettysburg being interrupted by zombies, and a huge earthquake splitting southwest California into a series of canyons lined with a new mineral called "ghost rock", which is basically coal that burns more efficiently but also makes creepy noises. And that's just for starters...

[[folder: Theme Parks]]
* The roadside attraction "[[http://io9.com/5084491/the-alternate-history-theme-park-where-dinosaurs-fought-in-the-civil-war Professor Cline's Dinosaur Kingdom]]" features an alternate version of UsefulNotes/TheAmericanCivilWar where [[NinjaPirateZombieRobot the Union army tried to arm itself with dinosaurs]]. [[EpicFail It didn't turn out so well.]]

[[folder: Video Games]]
* In Failbetter Games' browser game ''VideoGame/FallenLondon'', Victorian-era London was literally stolen by bats. [[spoiler: And it turns out the Masters of the Bazaar are ''literal'' Alien Space Bats. Makes you wonder if it's a deliberate reference to the {{Trope Namer|s}}, doesn't it?]]
* The ''VideoGame/{{Resistance}}'' series is based entirely around this trope, where the alien Chimeras arrive in TheTunguskaEvent of 1908. In 1921, Russia initiated a communications blackout with the rest of the world, and built a wall against its European border called the "Red Curtain". In December 1949, the Chimeran forces invade mainland Europe. The first game starts with their invasion of England in 1951.
* The backstory for ''DawnOfVictory'', a mod-in-development for ''VideoGame/SinsOfASolarEmpire'', is inspired by the ''Literature/WorldWar'' series in that it involves aliens invading during [[UsefulNotes/WorldWarII WW2]] and proceeding to kick everybody's ass, except for a few isolated victories. Then nukes are developed and used, pushing the Scinfaxi to the Southern Hemisphere. History then proceeds similar to ours in the Western world, except there are three superpowers: [=USSR=], Germany, and the Democratic Federation.
* In ''Robo VideoGame/{{Aleste}}'', the arrival of a mysterious foreign derelict ship introduces to Sengoku period Japan firearms, airships and HumongousMecha.
* Creator/ParadoxInteractive is normally known for creating highly-detailed, well-researched historical RealTimeStrategy games that try to err on the side of plausibility in modeling the setting. This is why several fans were, to put it mildly, taken by surprise when they launched the ''Sunset Invasion'' minor DLC for ''VideoGame/CrusaderKings II'', which introduces a massive invasion of Western Europe by [[{{Irony}} a technologically-advanced, disease-spreading]] [[{{Mayincatec}} Aztec Empire]].
* As of 2010, ''VideoGame/GuiltyGear'''s discovery of a physics-defying energy source that kicks off [[GeneticEngineeringIsTheNewNuke a genetically engineered monster apocalypse]] and turns the whole world into the cover of every metal album ever has officially become this.
* ''VideoGame/WolfensteinTheNewOrder'' has Nazi Germany beating back the invasion of Normandy in '44 and going on to win a WWII that lasts until 1948 through the use of [[StupidJetpackHitler extremely advanced technology]], decades ahead of anything the Allies can muster. They then proceed to colonise the Moon by 1951, and spread their lebensraum across 75% of the entire world by 1960. Early in the game, it's revealed that the reason for this was [[MadScientist General Wilhelm "Deathshead" Strasse]] discovering a secret cache of amazing, near-magical technology early in the war, and then reverse-engineering it to create unstoppable war machines. The irony, of course, is that the sect who made this technology-- the Da'at Yichud-- is ''Jewish''.

* The world of ''Webcomic/KevinAndKell'' was created by [[spoiler: time travelling intelligent birds from the future traveling back in time and preventing the existence of humans and [[UpliftedAnimal Uplifting]] all other animal species.]]

[[folder: Web Original]]
* Alison Brooks introduced the alien bats to [=soc.history.what-if=] in her AlternateHistory spoof ''[[http://www.changingthetimes.net/samples/brooks/original_alien_space_bats.htm Irony And Steal]]''. Here, the bats descend on Manchester, England at the start of the Napoleonic Wars, having learned how to [[AliensSpeakingEnglish speak English]] from [[AliensStealCable listening to future radio broadcasts]], and supply tanks to Britain with which it can defeat France at El Alamein. Silliness ensues, including the Russian Czar marrying a bat, [[ZeppelinsFromAnotherWorld dirigible arms races]], [[RichardNixonTheUsedCarSalesman Lenin becoming a baseball player]], and alien mutant ninja turtles replacing the population of Australia.
* On the Website/SpaceBattlesDotCom forums, an entire section of the site is dedicated to what they call "Random Omnipotent Beings," or "[=ROBs=]" doing precisely this, starting off many role-play threads.
** As a general rule, the ones that actually cause the implausible scenarios are referred to as "Bastard Random Omnipotent Beings", or "[=BROBs=]"
* The amount of WillingSuspensionOfDisbelief required to believe the point of divergence in Soviet history that sets up [[http://theboxingtribune.com/2015/03/what-if-klitschko-special-back-in-the-ussr-part-1/ the What If Klitschko Special]] is sufficiently high to drive that story into ASB territory---especially since it assumes that the events of ''Film/RockyIV'' are canon.
* AudioPlay/TheCartographersHandbook depicts a world that was overrun by a zombie-like plague in the 1870s and humanity's struggle to survive.

[[folder:Western Animation]]
* In the ''WesternAnimation/{{Futurama}}'' episode, "All the Presidents Heads", in which the cast go to the American Revolution to stop the Professor's ancestor David Farnsworth from betraying America, Fry accidentally messes with the signals key to Paul Revere alerting that "the British are coming", which creates a 31st century America that is still ruled by the British. Naturally, they make another trip to SetRightWhatOnceWentWrong.
* A similar timeline change occurs in ''WesternAnimation/BigGuyAndRustyTheBoyRobot'', when the Big Guy PoweredArmor ends up in the American Revolutionary War, until a British soldier discovers it and pilots it to defeat America, also forcing Rusty and the Big Guy's actual pilot to SetRightWhatOnceWentWrong.
* In ''WesternAnimation/StevenUniverse'', at some point before humans developed agriculture, the planet was colonized by an alien species called Gems, who eventually fought a civil war. This has clearly affected humanity's development, but it's pretty subtle and unclear of ''how'' exactly. There are numerous small differences (like Delmarva being a US state instead of just a landform), but then we see [[spoiler:a world map drastically altered by the early stages of HostileTerraforming, even sinking a huge part of what we know today as Russia into the ocean. And yet [[NeverWasThisUniverse some points of divergence seem to stem all the way back to Pangaea]], which split up differently from how it did in our timeline]].