A character, usually one relatively high on the power scale, loses a fight. Sometimes they die, other times they're just humiliated. The point is, they just got their butt handed to them by the other guys in a largely fair fight. Is this the end of our eternal rivalry between good and evil? Has one side truly triumphed!?
Not really, no. It turns out that the truly epic character we just saw get beaten up was Not Himself. Rather, he was Actually a Doombot, either a proxy robot or an impersonator who was pretty much impossible to distinguish from the genuine article until the writer told us so at the last minute — or later.
The narrative role of this trope is obvious: it works to prevent The Worf Effect or a Villain Decay, and also ensure that characters don't "really" die, thus allowing them to come back on next week's program. This can, nonetheless, still come off as an Ass Pull writ Shaggy Dog Story since there are rarely ever any clues given that the character was really a doombot, nor does it have any future relevance in the story. It's also a cheap trick since the other side is denied the feat of actually taking down the formidable character. Seldom will the characters (or the audience) ask what the difference is between defeating a perfect copy of the character and defeating the character himself.
The doombot may be used as well to fix a Continuity Snarl, or as a Reset Button of a Dork Age. The hero fought a classic villain the writer was not aware that's supposed to be dead? Easy: it was actually a doombot. Of course, the longer the period that the character was supposed to have been a doombot, the less credible the trick may be.
The trope is not simply for "it was actually a robot" plots: it must be used as a getaway resource. If the robot is a character in its own right, or if the replacement generates new plot directions, or is even the starting point rather than the outcome (for example in a detective story in a sci-fi setting), then this trope does not apply. If there is no personification, if the robot was simply a background element that nobody took in consideration, it means that The Dog (or whatever) Was the Mastermind.
A semi-popular form of Retcon. Often involves by necessity Ridiculously Human Robots. See Opening a Can of Clones for some of the negative results that crop up when this trope is used over a long period of time. Compare Fighting a Shadow, Backup Twin, Decoy Getaway, Cloning Gambit, Ninja Log, Remote Body, and Robot Master. If the original simply comes back with little or no explanation, then it's a case of Joker Immunity.
Noteworthy are the episodes when a criminal turns out to have not only one Doombot, but a whole number of them, and the one in which the Major "dies", which is straight from the manga.
The interesting thing about the former is that it turns out the process of making these doombots actually killed the original. All that's left are the doombots, and they're basically indistinguishable from the original.
Done in one occasion in Naruto when the good guys struggle against two very powerful villains and finally defeat them, only to find out they merely defeated inferior copies made out of animated corpses. From exchanges made beforehand, it then becomes clear that the copies only had 30% of their chakra to work with.
There was a partial example later: When Kisame fought Killer Bee, the real him was there for most of the fight but was switched with a much weaker duplicate by the end. Granted, there's a very good chance that Killer Bee and the Raikagereally could have beaten the real him together.
InuyashaBig Bad Naraku uses this repeatedly with dolls to the point where later in the series the heroes just assume certain incarnations are fakes.
Outlaw Star does this in episode 9 when Gene is attempting to collect a bounty on the criminal Zomba. Gene wins the fight and is surprised that the guy's a cyborg and takes him in only to find out the real Zomba wasn't a cyborg. Subverted immediately after when Suzuka walks out of the police station and as she's walking away some people come running up and announce that she's the one who took down the legendary Zomba (completely offscreen).
.hack//SIGN does this in episode 26. Tsukasa, Subaru and Mimiru are in a secluded location separated from the others. As the three encounter each other they find themselves being hostile. Tsukasa calls out a fake Mimiru which dissolves into several small data bugs before taking them into Morganna's lair.
In Mega Man Megamix, near the beginning of the The Greatest Enemy in History story arc, after Copy Mega Man foils Dr. Wily's plans, he shoots him in the forehead, only for the head to start bouncing on a spring, revealing it be a robot fake. The real Wily observed the event from his Wily Capsule, shocked at how Mega Man would shoot a human.
The name comes from Doombots which are used by writers in the Marvel Universe to explain how Doctor Doom rarely ever actually "loses" battles.
This has been pulled so often, there's a fan theory that the real Dr. Doom has never appeared in a comic. Or maybe even that there is no "real" Dr. Doom.
There is also the possibility that Doctor Doom does exist, but not in a true physical form. He might be an electromatic source of dark energy that makes the Doombots that he takes possession of until they get destroyed.
A doombot also appears in Runaways, but it's actually Ultron's.
Inverted in a 2005 Hercules miniseries, where Herc was tasked with a modern version of his twelve labors for a reality television series. One of his new labors was to sneak into Latveria and run off with a Doombot, but it's suggested that Herc screwed up and grabbed the real Doom instead (he gets credit for succeeding anyhow).
Early in Walter Simonson's run on Fantastic Four, he has the FF face a Doctor Doom who's wearing a new suit of armor — and who claims that every single Doom they've fought for the past 25 years of real time (since the Lee/Kirby days) has been a Doombot. Since this retcon includes things like Doom's appearance in Secret Wars and the entirety of John Byrne's run (regarded as one of the definitive eras for Doom), everyone since has assumed he was lying or a deluded Doombot himself, as there have been other Doombots that thought themselves the original.
For a long time, comic book fanlore claimed that Simonson had compiled a list categorising which appearances of Doom were real and which were actually Doombots, but he's since put paid to the rumour (not that it's stopped many fans from a) claiming he's fibbing about it, b) assuming that other writers who have worked on FF maintain similar lists, or c) creating such lists of their own!).
The first arc of The Winter Soldier comic implies that Doom actually programmes several Doombots to believe themselves to be the real Doom, to make them more life-like.
Hilariously, one of Doom's only defeats that never got an official Doombot retcon was when Squirrel Girl took him down (more info on her page).
In a small Marvel event Over the Edge, The Punisher killed Nick Fury. Later it was revealed that it had been an android.
Happens quite a bit with Nick Fury, who has had "Life Model Decoy" robots as a standard part of his stock-in-trade ever since he joined S.H.I.E.L.D.. Several 1960s stories had Nick Fury-shaped LMDs slaughtered by HYDRA and other foes. They had little to no other function or characterization. A 1977 Defenders storyline was the first to introduce a Fury LMD with some individuality, and later that year the real Fury faced a LMD version of himself with independent thought and ambition. Since then several stories have featured LMDs with some degree of autonomy.
A major S.H.I.E.L.D. storyline of the 1980s "revealed" that several key SHIELD-affiliated characters had been replaced for quite some time by LMDs controlled by a HYDRA-created android, the so-called Deltite. The storyline, termed the Deltite Conspiracy, featured LMDs of Laura Brown, Nick Fury, Eric Koenig, Sidney Levine, Clay Quartermain, Jasper Sitwell, Jimmy Woo, and even Obadiah Stane (a major opponent of Iron Man). As well as an unnamed female LMD who was apparently a combination of Laura Brown, Gail Runciter, and Valentina de Fontaine. (Brown and de Fontaine being love interests of Fury, and Runciter a love interest of Captain America.)
Original Sin has revealed that Possibly all modern day appearances by Fury have been LMD appearances. The original? Still alive, but much older.
In the Marvel Universe, Big BadThanos has duplicates called Thanosi that are indistinguishable from the original. Like Doombots, these are used (usually by Thanos creator Jim Starlin) to explain away defeats. Particularly more embarrassing ones.
His first appearance turned out to be a robot duplicate.
There was a War of theRetcons about the Thanosi and Squirrel Girl, where S.G. defeated Thanos offscreen in a Great Lakes Avengers miniseries, and the Watcher was dragged on to say "This is definitely the real Thanos" — and then in a different book some time later, Thanos casually mentions that he can create Thanosi that can fool even the Watcher. Just to make this even more ridiculous, the original story and the Retcon were written by the same guy.
Squirrel Girl's entire gimmick is defeating powerful villains like Doom and Thanos, usually off-panel, with it being left ambiguous whether it was Actually a Doombot she fought.
Spider-Man's enemy Mysterio uses this trick a lot too. Seeing as Mysterio is also fond of holograms and illusions, Spider-Man often cannot tell if he facing the real Mysterio, an illusion, or a robot, and even worse, the same often goes for a lot of other stuff he has to fight when the villain is involved.
This has become more complex since the original Mysterio acquired a couple of imitators who also use this identity. And they don't really get along with each other. A storyline in Friendly Neighborhood Spider-Man #11-13 (October-December, 2006) had all three Mysterios independently seeking a confrontation with Spidey, resulting in a rather complicated Mêlée à Trois scenario. With Spidey having trouble telling which is which, and further confused because the original was supposed to be dead.
In Spider-Men, Mysterio doesn't actually have an Ultimate Marvel counterpart. "Ultimate Mysterio" is actually a robot double he was controlling all along.
Perhaps the most infamous usage of this trick in Spider-Man history is the first "death" of Aunt May. She peacefully died of old age in a realistic and tasteful manner; Peter and the other characters mourned her and eventually moved on. However, later editor-in-chief Bob Harras demanded that she be brought back to life. So, Aunt May was found alive and it was revealed that Norman Osborn had hired an actress to impersonate Aunt May perfectly, and kept up the charade even on her deathbed, meaning Peter (and the readers) cried over a total stranger.
Another famed Spidey villain who does this trick in the Hobgoblin, Roderick Kingsley. Despite being souped up with the Goblin Formula, he isn't stupid - he'll send out random schmoes powered up and brainwashed to do his bidding and if they die, no skin off his back. If they do good, then he's more than willing to let them keep going, but if they screw up, he'll step in personally and kill the schmook himself. Just ask Jason Macendale... oh, wait...
Marvel's Mephisto has sometimes been impersonated by lesser demons who imitate his form. Such demons are defeated far more easily than the virtually invincible Mephisto.
Iron Man's enemy/occasional love interest Madame Masque had had so many contradictory interpretations and seeming deaths over the years that Kurt Busiek finally declared in an issue of The Avengers that the real Madam Masque was a reclusive paranoid who interacted with the outside world mainly through Expendable Clones who occasionally went rogue and defied her wishes. One of them even became an Avenger.
This is revealed to be the case during Final Crisis for the New Gods and Darkseid. All that earth has ever seen is somewhat limited projections of the real gods which operate on a higher plane of reality.
And then there's Prometheus, a DC villain who was created to be a sort of anti-Batman who was so intelligent and well-trained he could almost take out the entire Justice League on his own. Except that he had long since fallen prey to Villain Decay and had been reduced to just another generic baddie who gets his butt kicked by whatever hero happens to be around. The Justice League miniseries Cry for Justice attempted to fix this by revealing that the real Prometheus had been in hiding since he almost killed the JLA, and the loser who kept getting kicked around all these years was an impostor, who Prometheus had killed. But now the real deal was back, ready and able to...get killed off in short order by Green Arrow. It was quite a waste, but not nearly the worst thing about that series.
There were hints that Prometheus would actually return in some form, as both his helmet (which contained most of his knowledge) and the lobotomizedbody of his sidekick, I.Q., were later shown to be missing. It seems like there was a plan that was regulated to an Aborted Arc thanks to the New 52.
Professor X's first "death" in the X-Men comics was actually the shapeshifter Changeling having taken Xavier's place some issues earlier since he knew he was going to die anyways.
Geoff Johns invoked this very same trope the very next issue ofAction Comics where every single appearance by Brainiac in the Post-Crisis DCU, prior to Johns' "Brainiac" storyline was actually a "Brainiac probe". Even Milton Fine wasn't possessed by Vil Dox's disembodied intelligence, but by nanoprobes. It seems no trope was too overused in Johns' quest to bring back the Silver Age into the Superman saga.
Viper/Madame Hydra is a long-running Marvel villain who has appeared in many series. She had an out-of-character appearance in a storyline featured in Punisher War Journal #45-47 (August-October, 1992). Where she served as an ally to Daredevil, Nomad, and The Punisher. A year later, Gregory Wright wrote a story where it was revealed that Viper has been using look-alike "Pit-Vipers" to act in her name. The "Viper" appearing in the Punisher storyline was a rogue Pit-Viper with her own agenda.
In one of the The Batman Adventures comics, it was revealed that the redesigned green-skinned, elfin Poison Ivy that appeared in the later episodes of Batman: The Animated Series was actually a Plant Person created by the real Ivy to keep up appearances in Gotham while she went on the lam and shacked up with Alec Holland. Disturbingly, the plant actually thought she was the real Ivy right up until the end when she fell victim to Clone Degeneration.
Played with in the Marvel crossover Secret Invasion, but instead of robots, it's with Skrulls, shape-shifting aliens. It begins with a character who is revealed to be a Skrull, who managed to stay undetected, and the whole story is about the paranoia of who else may be an undetectable Skrull. And then it got to the controversial Civil War: the New Avengers were so damn sure that Stark only did the things he did because he was secretly a Skrull, and Stark suspected that Captain America's resistance to the Registration Act may had been because he was a Skrull... but no. Secret Invasion was not used as a Reset Button of anything, and did not organize or start any of the recent disasters. Stark and Rogers in Civil War were both themselves, Hulk in World War Hulk was himself (and the creature that destroyed Planet Hulk to make him go in a rampage of revenge, too), Quicksilver was himself when he stole the Terrigen crystals and started a war between The Inhumans and the human race, the Scarlet Witch was herself in Avengers Disassembled (and The Wasp, who reminded her of her lost sons, too), and also in House of M (and Quicksilver, who made her change reality, too), and so on. The Skrulls were simply in the background, trying to take advantage of the things happening, but not causing them.
Played with up to eleven by Quicksilver. After the Secret Invasion, he tried to clean his name of his recent disasters by claiming, in-universe, that he had been replaced by a Skrull. Of course, that was not the case, and Jarvis and Henry Pym (who were real hostages) realized that he was lying in the same page.
Perhaps the most outrageous example is Marvel's "Earth A" reality, where heroes like to take vacations to the main Marvel Universe, where they tend to act in manners contradictory to their counterparts, leaving our normal heroes to clean up the mess. This includes things like She-Hulk sleeping with the Juggernaut, or the Young Avengers joining the Initiative during the Civil War. In other words, this provides a rather cheap way to retcon any previous character action that the writer disapproves of.
A fairly literal example from Big Bang Comics — Ultiman hints that he has never actually met his archenemy Cortex, and that Cortex commits all his crimes by way of a series of robotic doubles. This isn't a secret on Cortex's part, and he tends to destroy the doubles himself by having them self-destruct upon their capture.
The Super-Adaptoid is an AIM-created robot which has plagued the The Avengers since in 1966. Because of its Power Copying abilities it is rather difficult to take down. A 1993 Spider-Man story had it serving as a Living Weapon henchman and easily defeated by a Badass Normal opponent. Which interfered with developments in other titles where the Adaptoid was revealed as the Diabolical Mastermind behind the efforts of AIM to become a power player in the world stage. As an explanation the Super-Adaptoid of the Spider-Man story was retconned to an inferior copy of the original.
The return of Blade's arch nemesis Deacon Frost was explained by him being able to create scientific doppelgangers of himself. He can create these (vampiric) copies from other characters as well, as seen in The Tomb of Dracula where he made an evil version of Blade.
The latest iteration of X-Force revealed that Cable has been making clones of himself and sending them out. The real one is in stasis, his body being awakened long enough to gather blood for a clone. As one clone states "He dies a little for two minutes. We die everyday."
General-Admiral Makarov from the Pony POV Series apparently has a habit of doing this to avoid assassination attempts. He also does it after being defeated by Cadence and shot in the head by Dima. Justified as he's a Reality Warper capable of replacing himself with a robotic copy at will, and a Parody Sue who uses this for it's normal narrative effect of avoiding admitting he was beaten.
Good guys can use this trick too. As seen in The Phantom Menace, Padme did this all the time as Queen of Naboo, disguising herself as one of the Queen's handmaidens while a bodyguard (Sabé) disguised herself as the Queen. And she was not the first Queen of Naboo to do this. Her head of security Captian Panaka designed the strategy, and it was used by her predecessor (and presumably, her successor).
In order to maintain Cthulhu's aura of menace and mystery, some stories and fan theories say that the Cthulhu that was driven back to sleep in the original short story "Call of Cthulhu" was merely a Spawn of Cthulhu instead of the Real McCoy.
The new Foundation trilogy novel Foundation And Chaos has an interesting version of this when Ridiculously Human Robot Dors shoots a similar style of robot, since Dors believes said robot is fundamentally damaged. it turns out the robot she shot was a remote-controlled duplicate of the real robot.
Isaac Asimov's "The Tercentenary incident". In 2076, the tricentennial of the United States, the country is ruled by a populist jerk, who is quickly losing support. He began to shake people's hands in the street, and suddenly explodes, becoming a pile of dust. Then he showed up at the balcony, and pointed that it was is a malfunction of his protocolar robot duplicate. He gave the "Tricentennial adress" (much better than his usual style) and strengthened the unity of the federation. And two years later... a guy shows up with very sound reasons to suspect that the president has been murdered that day, and that the robot, posing as human, has been acting as president since then.
Used with the Buffybot, a robot replica of the title heroine. A good example is the end of season 5, where Buffy apparently gets decapitated by the Big Bad, Glory. Lo and behold, the real Buffy then reveals herself, showing the first one to be a fake.
Season nine opens with Buffy's arms feeling funny. Later in the series we see a shot of Andrew working on a robotic arm, then in a fight Buffy's arm is torn off to her horror. When it turns out that it's a robotic arm, remembering how upset she was when there was a robot version of her before, Buffy\robobuffy gets even more upset.
Becomes Comically Missing the Point when she finds out she's a robot after her arm is ripped off and goes to confront Andrew about it. Instead of explaining why she's a robot he seems to be only concerned about getting her a new arm. Later when Buffy and Spike are angry at him because what she's been through because of it, he still thinks they're referring to her having lost the arm.
In Season 6 of Buffy the Scoobies use the Buffybot to make the underworld think that the Slayer is still protecting Sunnydale. When a vampire accidentally discovers this, it provokes immediate Rape, Pillage, and Burn by demon bikers.
The first time Willow gets her mitts on Warren in Season 6 of Buffy. Fizz crackle pop.
An instance of this appears on Angel, as well. A cyborg uses a Glamour to imitate Wesley's father. When the cyborg threatens Fred, Wesley shoots it dead, revealing its true nature. Unlike most cases of this trope, the duplicate was not operating on behalf of the original.
Stargate SG-1: System Lord Ba'al inherited Asgard Cloning Technology from his old master, Anubis. This let the writers kill him at least once almost every time he appeared after that. One episode revolved around SG-1 tracking down the lot of them. Or did they? Turns out, they didn't. Either that, or he just made more clones afterward.
Also on Stargate SG-1, in the season 4 episode Double Jeopardy, SG-1 finds out that their robot clones from season 1's Tin Man have been going on their own adventures. The second indication that SG-1 isn't really SG-1 is when Carter was surprised to be referred to as a Major rather than a Captain.
Farscape: Unbeknown to the audience, Aeryn Sun is swapped with a biomechnical replica to hide the real one's abduction. John Crichton doesn't awaken to the situation until the "bioloid" inadvertently fails at a Trust Password. Crichton draws a gun on her and, during an increasingly-agitated round of questioning, the faker tries to draw hers as well. Crichton blasts the side of her head off, revealing her inner components for all to see.
Doctor Who: An interesting variant occurs in "A Good Man Goes to War" when it is revealed that the baby Melody Pond the Doctor and his allies have just rescued is a Ganger.
Ultimately, this trope is the driving force behind the entirety of new season 6, as the over-arcing plot concerns the Doctor dying at River's hand being a fixed point in time. Fortunately, at the half-season mark they meet a group of people who specialize in robots that can imitate people...
Which turns out to be a misdirection as the Doctor escapes his death by using a Teselecta, an actual robot impersonating the Doctor, aligning quite well with the trope
Smallville: Lana Lang is caught in a car bombing, with enough DNA evidence to confirm the death, in season 6 finale. In the next season it is revealed that it was actually her clone created by Lex.
The Mentalist: Protagonist Patrick Jane tracks down and kills his almost-lifelong nemesis, serial superkiller "Red John", season ends. The next season begins, and, hey, what do you know: that guy Jane shot? He was actually just a boring minion of Red John's, or maybe even only an unrelated copycat.
In Dino Attack RPG, Ogel was killed three times during the Final Battle and yet still managed to survive. Wondering how? Each time Ogel apparently died, it was actually one of his Skeleton Drones in disguise, as a reference to the March/April 2001 issue of LEGO Mania.
It's probably only a Doombot if he loses... or the next writer disagrees with how the battle went.
Chrono Cross pulls this early on, when building up Lynx as the Big Bad, before the party finally fights him...a third of the way through Disc One? Don't worry, after you beat him, he turns into a strange mix between a cat and a Displacer Beast, and the real Lynx reveals that it was Actually A Shadow. There was no way he was going to risk fighting against Kid, who was so hell-bent on finding him.
Robotnik pulls this stunt after you first defeat him in Sonic Heroes, regardless of which team you play as. Subverted when the robot melts into goo, then reforms into Metal Sonic, revealing the whole thing to be a ploy.
Super Mario Bros. 1: In the original game you beat Bowser every four levels. However, each time but the last "Bowser" just turns out to be a different mook in disguise.
This returns in Super Mario 3D Land, with the fake Bowsers being a Goomba (World 1) and a Magikoopa (World 5) with Tanooki Suits.
In the fangame Super Mario 63, the Bowser in the Koopa Clown Car you fight before ascending the Meteor Tower is a robot.
Luigi's Mansion The "Bowser" towards the end of the game is clearly a mechanical decoy (though fairly accurate/lifelike) used by King Boo with his magitek on it. Therefore, King Boo is a boss in disguise here. This idea may very well be based on the fake Bowsers from Super Mario Bros..
In Streets of Rage 3, at the end of stage 5, you fight Mr. X much like you did in the previous two games, but he is revealed to be a robot. Given that the back story of the Western version is about robots replacing important public figures, you already fought a robot Axel in stage 3, and there are three more stages after stage 5, it didn't come as a huge surprise.
The Magic Emperor's first boss battle in the various remakes of Lunar: The Silver Star. Actually not the case in the original; you fight the real thing in your first fight with him and then leave him for dead, then one scene later and reveals he's alive and turns into a monster for the final fight.
Star Fox 64 has this happen during the standard ending: the Big Bad you just killed was actually his robot duplicate. The true ending has you battle the real Big Bad.
Zalazane is not only dead, but was explicitly dragged off to voodoo hell or whatever. He ain't coming back.
Dr. Wily has pulled this on multiple occasions, to the point that Mega Man 9 lampshades it.
Wily's first instance of this is in Mega Man 2, where he appears to morph into an alien, but it's just a holographic projection.
In Mega Man 3, after you defeat the Spider Tank boss in the penultimate stage, Wily is thrown from the machine as usual, but it turns out to be a decoy.
Sigma has also done this frequently, coming back inexplicably in a arsenal of different forms- until his current defeat in Mega Man X8. Justified by the fact he is a living virus and can exist as a digital entity, then integrate into a new body at will. In X8 Lumine, a seemingly gentle Reploid director, forcefully states at the Sigma is gone for good, standing over his broken remains- only to reveal his ''true'' intentions a half-second later. Some time in the distant future, this is disproven: Sigma still lives on in viral form. However, with the end of the Maverick Wars, his programming was forcefully and permanently deleted by the antivirus program of the Mother Elf.
Subverted in Mega Man Zero 4: Both Dr. Weil and Zero (although debatable) die, but live on as individual Biometals in the Mega Man ZX series. Double Subverted if you count Model Z's sacrifice in ZX Advent.
In Jet Set Radio Future, a story arc has team member YoYo betray the entire group. Or so the Golden Rhinos would have you think, as they kidnapped YoYo and built a robot clone and loosed him on Tokyo to wreak havok.
In Scott Pilgrim, The final fight with Gideon turns out to be an example. Overlaps with Clipped Wing Angel in that after beating the robot, the real Gideon goes down in a single hit.
Lord Nemesis in City of Heroes has so many mechanical duplicates of himself running around that when fighting his minions, it's not uncommon to find multiple enemies named Fake Nemesis in the same building, or even in the same patrol.
There even a bug which can occasionally result in a group of enemies composed solely of a half dozen or so Fake Nemesis.
It's actually been suggested that, due to Quan Chi's involvement in the plot of 9 (despite not being one of the characters from the original trilogy) and The Stinger (where Shinnok appears and discusses future plans with his underling, setting up the new continuity's version of Mortal Kombat 4), Shinnok's status as one of the few survivors of Armageddon allowed him to pull a Raiden and send a message to his past self (and likely with much greater clarity than Dark Raiden did), allowing him to play The Chessmaster using Quan Chi as his proxy.
In Vanquish, you fight with seemingly two Victor Zaitsevs, one red and the other blue. After killing the first one, no matter which, Zaitsev will say you killed the wrong one. Unfortunately, Zaitsev was never there to begin with; they are both just doombots.
In the Game Boy version of Kid Dracula, the first Garamoth you fight turns out to be a robot being piloted by an alien.
In the G.I. Joe arcade shooter, the first battle with Cobra Commander is really a robot knockoff.
Fire Emblem Akaneia does this twice. In the first game, Big Bad Gharnef creates two clones of himself during his chapter. Stat-wise, the clones look identical to the real Gharnef, and the game acts as though they're immune to non-starlight damage, but they really aren't. The real one could be any of the three (it's random, and changes every time), but you'll know a clone when you kill it because they don't have death quotes. They also all appear to be carrying the Falchion, but two of them are fakes... which, interestingly enough, also follow this trope: their stats show up the same as the real one, but when dropped they turn out to be just an ordinary Steel Sword.
In New Mystery, the Roro you fight as the boss of Chapter 6x turns out to be just a clone. You won't fight the real Roro until 12x... where he's accompanied by an entire army of Roros. There are three 'boss' Roros with slightly higher stats, and a whole bunch of Mook Roros. The Mooks spawn constantly until you kill the real one, which could be any of the three 'boss' versions. (like Gharnef, it's random) This trope is also discussed in-story, it's implied Roro has taken this to such extremes even he doesn't know which of his clones is the real one anymore.
In Marvel Avengers Alliance, Mission 3-5's Epic Boss is not just one, but three Doombots. And the trope gets lampshaded by the characters, to boot.
In Final Fantasy VIII the SeeD and their clients the Timber Resistance get the opportunity to kidnap the President of Galbadia (who at this point is thought to be the Big Bad) and do so. However, this "president" is not just a decoy, but an undead construct created by the Sorceress Edea to trick the Timber Resistance.
Towards the end of Bob and George, Bob kills Dr. Wily. Or rather, he kills one of the many robotic clones Wily leaves scattered around his fortress on the off chance a deranged psychopath breaks in and attempts to kill him.
Wily: It worked, didn't it?
Least I Could Do mocked the hell out of this trope during their Crisis Crossover parody arc: Rayne gets killed off more than once, and every time, "It's cool. Was a clone."; after a while, his roommate decides to give it a try by snapping Rayne's neck; turns out he was the real Rayne, who gets quickly replaced by a clone who spent a year in a prehistoric cave with Batman. No, really.
In Sluggy Freelance Dr. Schlock has had inflatable, robot decoys deal with dangerous people in his place many times, particularly as he's become more paranoid over the years.
Parodied in The Adventures of Dr. McNinja. Dr. McNinja is fighting Dracula on Dracula's moon base (don't worry, it makes even less sense in context), and after setting up a decoy of himself to fool Dracula grabs him and is about to destroy him by exposing him to sunlight. Then, of course, it turns out it's actually a Draculabot — goodness knows when the switch was made, and going back in the story to look for a likely spot only makes it look less plausible. Oh, and since he jumped offthe moon in a spacesuit while holding on to the Draculabot, he then has to surf it down to Earth, which counts as kind of extreme even by his standards.
After Bowser loses a minigame during a Mario Party 6, upon returning to the main map, he gloats about how he's going to punish the losers, then acts shocked that nobody lost. The Mario Party Tv group joke that they must have fought a 'Bowser bot' instead.
Used on more than one occasion in episodes of Super Friends to explain how the latest scheme by Lex Luthor didn't actually work, since the heroes were being represented by robotic duplicates. Raises the question of why the Legion of Doom doesn't bother with autopsies, or why they throw away their latest superweapon the minute the Super Friends "appear" to be dead.
In the first season finale to Filmation's Flash Gordon, Ming appears to die, but the corpse is revealed as a Ming-bot, and the real Ming flies away cackling that he will regain his throne and have revenge. The implication, at least, is that it was the real Ming who had lost a fight with Flash a few minutes earlier, but that he had pulled the switch when he and Flash were briefly separated.
Megamind. In the final battle against Tighten, Megamind rescues Roxanne but is killed—only to be revealed as Minion wearing a holographic disguise.
Slade used this trick a lot in Teen Titans, using an android duplicate of himself to both fight the Titans and deliver the occasional taunt from a remote location. The episode "Haunted" was the most dangerous example, proving that Slade could be a downright deadly threat to a hero's life and sanity without being there at all (This time it was a hallucination, not a robot). At least one was rigged to explode if defeated, and most had monitors behind their masks to facilitate last-minute megalomaniacal gloating.
In The Spectacular Spider-Man, whenever Quentin Beck/Mysterio is captured or defeated, it always turns out to be a robotic double.
In an episode of Batman: The Brave and the Bold, Superman and Batman captured Lex Luthor early in the episode. It turns out that Lex Luthor is actually a Lexbot.
In the Young Justice episode "Welcome To Happy Harbor", Miss Martian shockingly executes Bromwell Stikk, the pilot of the Mister Twister mecha. We quickly discover that Stikk himself was an android built to resemble the real pilot, and that he had a built-in camera meant to spy on the kids. She guessed it was an android because she couldn't read its mind.
The young T.O.Morrow seen was actually a robot, the real one was old man who's hooked on life support.
This trope is flat-out abused by Tweetums in the series finale.
Two episodes of Inch High, Private Eye featured a mad dollmaker as a villain. In the first, sold clockwork manikins to department stores that would rob them. In the end, he's arrested but a failed escape attempt reveals that they only caught a robotic duplicate. Due to the prevalence in Robotic Reveal in the cartoons of the era the main characters never even consider the possibility that the real guy is still at large... until he comes back with robotic duplicates of the main character and his boss, and successfully ruins their reputation.
Super Chicken: One episode started with Villain of the Week Dr. Gizmo being taken to prison but it turns out it was a machine. In the end, he tried the trick again but the Super Chicken distracted capturing him was another one. The real Dr. Gizmo was captured by the real Super Chicken.
The Venture Bros.: In "O.S.I. Love You" it's revealed that the Sovereign is not really David Bowie, but rather a shapeshifter acquaintance of his.
Challenge Of The Superfriends had another example of good guys using this trick. The Legion of Doom found out about a sealed away weapon that could act as a lethal death ray to the heroes and tricked Superman into breaking the vault open. (That's right, this episode suspended the show's Never Say "Die" policy. As for what madman invented such a device, they didn't say.) The Legion of Doom were apparently then able to decimate the heroes mercilessly, often in front of terrified citizens. When it seemed all the heroes had perished and the villains had achieved complete victory, Luthor saw no further need for the thing, and casually threw it away. A terrible mistake. A day later, the Superfriends reappeared, and after pulping the villains, revealed that they had been hiding in their satellite base (presumably a sort of precursor to the Watchtower) while using android duplicates created by Superman in the Fortress of Solitude to make the Legion believe they had been killed. Once Luthor threw it away, the Apache Chief went into the sewer in protective clothing and destroyed it, permanently. (Of course, when you think about it, the Legion of Doom should have been suspicious when they seemed to win so easily...)
Dictators usually have an array of body doubles and impersonators working as the target of assassination attempts. Hitler himself managed to survive 42 assassination attempts through a combination of this trope and a ridiculous amount of luck (due to the number of Contrived Coincidences that managed to thwart an attempt in one way or another).
Part of military strategy involves disguising one thing as another in order to steal a march on the enemy. For example, as part of the Raid on St Nazaire in WWII, the British destroyer Campbelltown was disguised as a German frigate (hoisting its flag before firing, of course).
Two special mentions for pirates and guerrillas. Unlike fictional portrayals, pirates did not fly the Jolly Roger flag: they concealed their true nature by flying flags of known countries, to get near other ships without suspicion. Guerrillas try to balance their lower military strength by concealing themselves among the civilian population.
American rapper MF Doom has been known to send impostors to concert events for which he is on the bill.