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"What happens when an unstoppable force meets an immovable object?" is one of the most famous formulations of a YinYangClash in the Western consciousness. As a result, it's become a StockPhrase for describing any conflict between particularly strong or [[{{Determinator}} particularly stubborn]] individuals.

Some people try to claim that the unstoppable force would just bounce off and continue moving, albeit in a different direction (according to Newton's third law of motion, and convention of energy and momentum... you know: {{s|paceDoesNotWorkThatWay}}cience). For this reason, the question is sometimes phrased using the term "irresistible force" instead.

'''Please note:''' This article is about the actual phrase itself. If two really strong guys fight, and no one compares them to an immovable object and an unstoppable force at any point, then the example belongs in UltimateShowdownOfUltimateDestiny or YinYangClash.

Unrelated to XMeetsY.

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!!Examples:

[[foldercontrol]]

[[folder:Anime and Manga]]
* In ''Anime/{{Pokemon}}'', Rampardos is described as the unstoppable force/spear that can break any shield and Bastiodon is described as the immovable object/shield that can't be broken.[[note]]This actually comes from a probable origin of the phrase, where a Chinese merchant claimed to have a spear that could break any shield and a shield that would not be pierced by any spear.[[/note]] They battle. So you might be wondering what happens when Roark's Rampardos battles his father Byron's Bastiodon. The answer? [[EvasiveFightThreadEpisode The battle is interrupted due to Team Rocket before it can be resolved]].
* Alluded in ''Manga/{{Eyeshield 21}}'', when Yamato (the original bearer of the title) and Shin (the antithesis of main character Sena) met, [[LightningBruiser both are considered the unstoppable Runner and the strongest Linebacker respectively]]. The result is sort of definite though, with Yamato managed to drag Shin with all his strength...at snail pace. To say the watchers amazed is an understatement.
* In ''HoshiNoSamidare'', Yukimachi and Subaru's paired attack and defense directly allude to this - they call their telekinetic attack "the Strongest Spear" and their telekinetic shield "the Ultimate Shield." They pick the names from a story shared by their teacher, the Master, about a spear that could penetrate any shield and a shield that could block any spear. In the hands of a single warrior, that warrior would be unstoppable. The Master then clasps their hands together, declaring the two together to be "the warrior."
* Referenced in the anime of ''{{Trigun}}'' by Hoppared the Gauntlet, who declares himself as an invincible shield and [[TheGunslinger Vash's]] guns as an unstoppable spear.
* Discussed in SaintSeiya during Seiya's early fight with Shiryu and even referred to as such. In a twist, Shiryu's in possession of ''both''; his shield too strong for Seiya to breach while also having considerably greater raw strength at his disposal. Seiya ultimately solves the conundrum by tricking Shiryu into attacking him in such a way that when he dodges, he ends up punching into his own shield. [[spoiler: The shield breaks, but Shiryu also nearly breaks his hand in the process and is forced to continue the fight without his Cloth.]]
* In ''Manga/{{Naruto}}'', Gaara develops a technique called "Shield of Shukaku"[[note]]Or "Ultimately Hard Absolute Defense: Shield of Shukaku[[/note]], a giant Shukaku-shaped doll made of sand that is supposed to be impervious to most any attack. In the anime, he also demonstrates an attack-based counterpart called "Spear of Shukaku", which has yet to meet a defense it could not break. The names are in reference to the chinese parable mentioned above. Both are formed by Gaara using his sand to compress the hardest materials he can find under extreme pressure. Being used by the same person, they've yet to be seen hitting each other.
** The legendary Third Raikage possesses an impregnable defense and indefensible offense through using his lightning chakra cloak. The only way he could be wounded was to turn his attacks on himself.
** In yet another example(and probably the clearest expy of the spear and shield fable), Itachi's Susanoo possesses the Yata Mirror, a shield which can change characteristics to nullify attacks, and the Sword of Totsuka, a weapon which will seal anyone it hits in a dream-like state for eternity.
* According to GoNagai, ShinGetterRobo is the unstoppable force while {{Mazinkaiser}} is the immovable object.
* In ''LightNovel/{{Katanagatari}}'', the first of the Twelve Deviant Blades Zettou Kanna was supposed to be unbreakable. The second sword Zantou Namakura was supposed to be able to cut anything. When Shichika wondered what would happen if the swords clashed, Togame guessed that Zantou Namakura would prevail since it was forged later. [[spoiler:Confirmed in the end, when Shichika's Kyotouryuu, the final perfected Deviant Blade, easily shatters Zettou Kanna.]]
* ''Manga/DansaiBunriNoCrimeEdge'': Apparently the reason why the Crime Edge (an indestructible sharp pair of scissors that can cut anything) can cut Iwai's otherwise unseverable hair.
* According to director Mitsuo Fukuda, ''Anime/MobileSuitGundamSEED'''s Strike and Aegis Gundams were designed with the Eastern version of this paradox in mind: "What happens when a sword that can destroy anything hits an invincible shield?" Hence their {{Meaningful Name}}s; "Strike" as in what a sword does, "Aegis" as in [[Main/ClassicalMythology Athena's shield]].
[[/folder]]

[[folder:ComicBooks]]
* ''ComicBook/IncredibleHulk'' #272. Hulk and [=Sasquatch=] ram {{Wendigo}} [[http://i47.photobucket.com/albums/f188/A_Flight5/TheIncredibleHulkv2-272-21.jpg using downed trees, with Wendigo in the middle]].
-->The Wendigo becomes the immovable force between two irresistable objects.
** This phrase is more overused in The Hulk than anywhere else. Whenever the writers want [[strike:belabor]] impress that an opponent is a serious physical challenge to Hulk, they will be one of these, and Hulk will be the other.
* Invoked directly in the second ''{{Franchise/Superman}} / ComicBook/SpiderMan'' crossover, when Superman calmed down The Hulk by planting himself to the ground and let the Hulk hit him, thinking that when he decided to become the Immoveable Object, no Unstoppable Force could move him. He also hinted that he didn't want the Hulk to get any angrier, or he'd become more than even ''he'' could handle.
* Grant Morrison's ''ComicBook/AllStarSuperman'' has Superman being asked this question. His solution? "They surrender," which could be a ShoutOut to the aforementioned Superman / Hulk confrontation - that's ''precisely what happened''.
* When former {{ComicBook/X-Men}} writer Chuck Austen was asked in a interview; what would happen if the unstoppable {{Juggernaut}} runs into the immovable {{Blob}}? He replied...
--> "They'd pound on each other until they were both so exhausted that they'd just lay down and watch videos. Porn, of course!"
** The toy review site OAFE.net answered this question [[http://www.oafe.net/toons/quix/110601.php with a toy comic]]. Basically, they shake hands and say hi. (Which makes a lot of sense in-story: the Juggernaut and the Blob have both been members of the Brotherhood of Evil Mutants, although they are rarely on the team at the same time.)
** ''TabletopGame/MarvelSuperHeroes'' RPG, knowing its readers, provides an answer to this. "Juggernaut could move The Blob by destroying the ground underneath his feet, unless he was sitting on a planet made of Adamantium" (it didn't say what would happen in that case, however).
** One ExpandedUniverse novel had them fight each other. Juggernaut won, because Blob flinched before the impact. Marko internally noted that had Dukes not flinched, the collision would have been ''really'' painful.
* Back in the Silver Age, {{Superman}} and Superboy tried to test this out by flying into each other. They wound up with memory loss and ripped the Time Stream a new one.
[[/folder]]

[[folder:Fanfic]]
* A Naruto-Justice League crossover had Sasuke's sword of Kusanagi vs. WonderWoman and her gauntlets. The sword dented the gauntlets, shocking them both--Sasuke because it didn't cut through, Wonder Woman because it dented them at all.
* In the ''Literature/{{Discworld}}'' fic ''Fanfiction/NatureStudies'', Sam Vimes watches a showdown between a charging rhinoceros and Sergeant Detritus bracing to meet it head on. He reflects that Vetinari was banging on down at the palace about the old philosophical conundrum of what happens when the irresistible force meets the un-moveable object. He reflects the Patrician would give something of personal value to witness what happens next... and then the two met.
* In the ''Series/BabylonFive'' fic ''FanFic/AFightingChance'', a Minbari fleet charging a wall of [=EarthForce=] dreadnoughts who can see through their stealth is described as an irresistible force running in an immovable object. [[spoiler: The Minbari almost broke through, but at that point the human ships [[MacrossMissileMassacre fired thousands of missiles at them]], annihilating their fleet]].
[[/folder]]

[[folder:Film]]
* From ''Film/TheDarkKnight'', after Batman knocks the Joker off a building [[ThouShaltNotKill and then fires his grappling cable to save his life]]:
-->'''The Joker:''' Oh, you. [[PungeonMaster You just couldn't let me go]], could you? This is what happens when an unstoppable force meets an immovable object. [[IncorruptiblePurePureness You are truly incorruptible, aren't you?]] Huh? You won't kill me out of some misplaced sense of self-righteousness. [[ItAmusedMe And I won't kill you because you're just too much fun.]] I think you and I are destined to do this forever.
* ''Film/ImagineMeAndYou'':
-->'''H:''' What happens when an unstoppable force meets an immovable object?
-->'''Luce:''' It never happens. If there's a thing that can't be stopped, it's not possible for there to be something else which can't be moved, and vice versa. They can't both exist. You see? It's a trick question, is the answer.
** And later, when [[spoiler:Heck has decided to leave Rachel because he knows that she's in love with Luce:]]
-->'''[[spoiler:Heck:]]''' [[IWantMyBelovedToBeHappy I want you to be happy.]] More than anything else, I wanted to be the cause of happiness in you. But if I'm not, then I can't stand in the way. Do you see? Because what you're feeling now, [[spoiler:Rachel]], is the unstoppable force... which means that I've got to move.
* ''Film/TheAvengers'' - Thor's Hammer vs Cap's Shield. The result? The force of the impact doesn't hurt Cap, but is instead reflected into a shockwave that levels the forest for miles around. The phrase isn't used in the movie inself but in the wider MCU: Thor's movie called his hammer the ultimate weapon and Cap's movie called his shield the ultimate defense.
[[/folder]]

[[folder:Jokes]]
* [[RussianHumor A Russian joke]] runs like this:
--> Vovochka, what will happen if unstoppable force will affect unmovable object?
--> Vodka price will rise?
--> Why do you think so?
--> 'Cause my dad always says: First some weird crap happen -- then vodka price will rise.
* A generic quip on the subject:
--> Q: What happens when the unstoppable force meets the immovable object?
--> A: They have an indescribable accident.
* Another:
--> Q: What happens when the unstoppable force meets the immovable object?
--> A: ChuckNorris [[ChuckNorrisFacts dies]].
* Alternatively:
--> Q: What happens when the unstoppable force meets the immovable object?
--> A: That would never happen, Chuck Norris would never kick himself in the face.
[[/folder]]

[[folder:Literature]]
* Used as a riddle in the far-future section in Ian Banks' "Walking on Glass". The actual answer is randomly tossed out in the other narrative. [[spoiler:The unstoppable force stops, the immovable object moves.]]
* Only two people in the world of ''SoonIWillBeInvincible'' have "Invincibility" listed as a power...
* [[Literature/TheDresdenFiles Harry Dresden]] defines the [[BattleInTheCentreOfTheMind mind games]] between him and [[spoiler:Molly]] in this way. He has a big, obstinate castle (unmovable object) while her attacks are equivalent to several Mongolian Hordes (irresistible force). It usually ended in a draw and two headaches.
* In ''[[Literature/RiversOfLondon Whispers Under Ground]]'', after watching [[BigEater Zach]] chowing down on one of Molly's gigantic breakfasts, Peter quips about how the unstoppable cook is up against the unfillable stomach.
[[/folder]]

[[folder:Live Action TV]]
* Referenced on one episode of ''Series/{{Mash}}'', when Hawkeye and B.J. go on a bathing strike in response to [[ItMakesSenseInContext Charles' french horn.]] When Charles refuses to budge, Hawkeye prefaces their next gambit with:
** "Now it's time for the unstoppable force to polish off the immovable object!" [[note]] Note, I'm not sure if this is exactly right. Please change it if it's wrong.[[/note]]
* ''Series/ThatMitchellAndWebbLook'''s [[http://www.youtube.com/watch?v=VF_uOgyBK1c football promo sketch]] contains this (and the similar "The giants of Charlton play host to the titans of Ipswich, making them both seem normal-sized").
* Used in the ''Series/KnightRider'' episode "Trust Don't Rust", to describe the theoretical outcome of a head-on collision between KITT and KARR. They refer to it as "Zeno's Paradox".
* In an episode of ''Series/TheAdventuresOfSuperboy'', a professor asks Superboy to help transport an insanely heavy totem pole, referring to the pole as the immovable object and Superboy as the unstoppable force. The totem pole was so heavy that even Superboy had difficulty lifting it.
[[/folder]]

[[folder:Music]]
* The old Johnny Mercer standard, [[http://www.youtube.com/watch?v=Qc6tGS0YOdA here]] sung by Fred Astaire to Leslie Caron in 1955's '' Daddy Long-Legs'':
-->When an irresistible force, such as you,
-->Meets an old immovable object like me,
-->You can bet just as sure as you live,
-->Something's gotta give --
-->Something's gotta give --
-->Something's gotta give!
* ''{{Skyclad}}'' tells us in "[[BreakupSong You Lost My Memory]]" that
-->Unstoppable force and immovable object,
-->repel one another when by chance colliding.
* ''JanesAddiction'''s "Irresistible Force (Met the Immovable Object)".
[[/folder]]

[[folder:Myth and Legend]]
* A Greek story has a variation with a fox that can never be caught and a hound that can never lose its prey. Naturally, they're set on each other. Zeus, unable to tolerate this kind of paradox, [[TakeAThirdOption turns them to]] [[TakenForGranite stone]].
* An old Chinese legend concerns a blacksmith who makes both shields and spears. He first pitches a customer the spears, claiming that they are so sharp, no shield can block them. He then pitches the shields, saying they are so hard, no spear can pierce them. The customer then asks what would happen if he threw one of the blacksmith's spears at one of his shields...and received no answer. This is the source of the Chinese word for "paradox;" "矛盾," or ''modn'', literally translates as "spear-shield.''
[[/folder]]

[[folder:Professional Wrestling]]
* An oft-played clip from ''Wrestlemania III'''s iconic Wrestling/HulkHogan vs Wrestling/AndreTheGiant match: "The irresistible force meeting the immovable object."
[[/folder]]

[[folder:Sports]]
* The 1999 Jacksonville Jaguars won every game they played and were favored to win the Super Bowl...except they couldn't beat the Tennessee Titans. The Titans had dealt the team both of its regular season losses and eliminated them in Conference Championship game. For comparison sake, the Jaguars had scored 62 points in the previous game, but were held to just 19 against the Titans.
* The phrase was in wide use referring to the 2013 [[UsefulNotes/CollegiateAmericanFootball Big Ten Football Championship game]], which pitted the Ohio State Buckeyes against the Michigan State Spartans. Ohio State was known for their amazing offense, which had led the team to a 24-0 record over the two years since the appointment of Urban Meyer as coach, while the Spartans had, by universal agreement, the best defense in the country. The immovable Spartans stopped the unstoppable Buckeyes, 24-34.
** Likewise, this trope was at times referred to in the days leading up to SuperBowl XLVIII, which had two teams who were respectively the best in offense and defense for the 2013 season; the AFC's Denver Broncos (led by quarterback Peyton Manning) and the NFC's Seattle Seahawks (a.k.a. the "Legion of Boom"). [[SubvertedTrope Seattle defeated Denver right from the first snap]] ''[[CurbStompBattle twelve seconds into the game]]'', 43-8.
[[/folder]]

[[folder:Tabletop Games]]
* Given the [[OverNineThousand power levels]] that get slung around in ''{{Exalted}}'', it usefully has a rule for what happens when a perfect attack comes up against a perfect defense: Defense ''always'' wins.
* The ''VideoGame/WorldOfWarcraft'' TCG features the below mace and shield as cards, with the flavor texts of "What happens when... ?" and "Oh, that's what happens.".
[[/folder]]

[[folder:VideoGames ]]
* In ''VideoGame/WorldOfWarcraft'' there is a Mace called Unstoppable Force and a shield called Immovable Object; both were among the easiest to obtain Epic gear and really good... until the release of the first expansion pack made them next to useless.
** This also inspired the {{Joke Weapon}}s Stoppable Force and Moveable Object, two pieces of VendorTrash that were useless even when they were first released, except for the little gold they brought.
* In the ''{{Suikoden}}'' universe, the True Runes were said to be born after the Sword that could cut through anything and the Shield that could stop any strike clashed.
* ''VisualNovel/AceAttorney'': Edgeworth tells a story of a weapon merchant presenting gifts to a lord; a spear which can pierce any armor, and a shield which can stop any weapon. The lord immediately pointed out the contradiction, embarrassing the merchant. This story inspired the design for the present day Prosecutor of the Year trophy; a broken shield, and a broken knife. Thematically, it's the equivalent of Ancient Romes "''[[http://en.wikipedia.org/wiki/Memento_mori memento mori]]''", reminding prosecutors they are not unbeatable.
* In ''VisualNovel/UminekoNoNakuKoroNi'', During their duel in Episode 3, [[spoiler:Virgilia]] attacks Beatrice with the Divine Spear, and Beatrice deflects it with the Divine Shield. Ronove helpfully notes that this only worked because the irresistable force must never meet the immovable object.
* ''VideoGame/PerfectWorld'': A very early quest for human characters involves meeting the salespeople in Etherblade. Playing off the Chinese (spear/armor) version of this paradox, the blacksmith claims that his spears cannot be stopped by any armor, and the tailor claims that her armor cannot be pierced by any spear.
-->'''Player Character:''' [[DeadpanSnarker So if I bought one of the blacksmith's spears and tested it against your armor...]]
* ''VideoGame/LeagueOfLegends'': Xin Zhao has a [[EmoteCommand /taunt]]: "[[BadassBoast Find me an immovable object, and I'll put this question to rest!]]"
** Malphite's ''Unstoppable Force'' ultimate is now actually unstoppable. Before, you could knock him out of it by hitting him mid-charge with any stun or root.
[[/folder]]

[[folder:Web Comics]]
* Referenced in ''Webcomic/RealLifeComics'' [[http://www.reallifecomics.com/comic.php?comic=title-2766 here]]. The result in this case: [[spoiler: the immovable object wins.]]
* ''Webcomic/TwoGuysAndGuy'' references it too, but [[http://www.twogag.com/archives/2718 only]] for TheUnreveal.
* As of recent events in ''Webcomic/{{Homestuck}}'', Jack Noir and [[spoiler:Peregrine Mendicant]] seem to have this kind of battle going on, with [[spoiler:Peregrine Mendicant]] as the "Unstoppable Force" and Jack as the "Immovable Object".
[[/folder]]

[[folder:Web Original]]
* One of the many things the ''Wiki/SCPFoundation'' keeps track of is [[http://www.scp-wiki.net/scp-225 SCP-225]]: an immovable object, and an unstoppable object. They ''really'' do not want to find out what would happen if these two objects ever collided. They're drawing up planetary evacuation plans just in case.
** By their own admission, that might not be enough: ''Since all tests thus far have shown that neither SCP-225-1 nor SCP-225-2 can be damaged or moved by any means known, the possibility also exists that neither object would be annihilated, halted, or altered from their course even by contact with the other. If this is true, then a collision between SCP-225-1 and SCP-225-2 has the potential to [[[ThingsManWasNotMeantToKnow DATA EXPUNGED]]].''
* This was examined by [=MinutePhysics=] in [[http://www.youtube.com/watch?v=9eKc5kgPVrA this video.]] Their answer? An "immoving" object really refers to an object that is will not accellerate, since the concept of moving depends on the frame of reference of the observer. And an unstoppable "force" refers to an object that is moving, but cannot be accelerated (so they are really the same thing). Although they would require infinite mass, and thus, infinite energy, if these objects ''truly'' could not be accelerated, then [[spoiler:both objects would pass right through each other and continue moving. For an unstoppable force and an immovable object to exist, they must both be intangible.]]
* There are a number of abilities in ''Literature/{{Worm}}'' that are absolute and flat out break the laws of physics. For example, the Siberian is utterly invulnerable and [[TheJuggernaut cannot be impeded by any obstacle]], while another character can freeze objects in time, rendering them completely impervious to any force. Their collision is referenced by this trope, and results in [[spoiler:both powers being canceled out, with the frozen objects reverting to normal and the Siberian vanishing, as she is actually [[FightingAShadow a projection]].]]
[[/folder]]

[[folder:Western Animation]]
* In one episode of ''WesternAnimation/RegularShow'', this is what happens when Rigby learns the [[OneHitKill Death Punch]] in attempt to beat Mordecai at Punchies. Only for Mordecai to learn the Death Block and challenge him. The result is a stalemate.
* In one ''WesternAnimation/RobotChicken'' sketch, Zeus is giving Perseus (or possibly a Perseus action figure) magic equipment, including a sword that can pierce any armor and a shield that can stop any weapon, along with advice not to get them too close together since he isn't sure which one beats the other.
* In ''XMenEvolution'', the Juggernaut and the Blob are characterized as this by the Blob. Juggy manages to move the Blob but is considerably slowed.
* ''WesternAnimation/BatmanTheBraveAndTheBold'' episode "Emperor Joker!" has [[ImYourBiggestFan Batmite]] describe Batman's relationship with SelfDemonstrating/TheJoker as such. Likely in reference to ''Film/TheDarkKnight'' quoted above.
[[/folder]]
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