You Time Travel into the past; something happens as a result of your time travel, and somebody dies. Somebody important and probably even famous, who you know stayed alive until after this date. What can you do to close the Stable Time Loop, Set Right What Once Went Wrong, or at least trick out time so you can end up back in a Close-Enough Timeline to your own? Why, impersonate them, of course!
Usually, for added drama, the person you're replacing is supposed to die in some other way in order to trigger a significant event, meaning that you expect replacing them to lead to a Heroic Sacrifice. This is not to say that it actually does, though; you can often find a third option besides dying nobly in the past and screwing up the timeline.
There is also a variation in which the time traveller doesn't cause the historical figure's death, but instead discovers that the historical figure never actually existed; the time traveller then has to impersonate the historical figure in order to create the history he remembers.
Compare and contrast Time Travel Escape; in particular, the third option in the more-dramatic version often involves pulling something like a Time Travel Escape. Also compare Beethoven Was an Alien Spy, which is a supertrope to at least the Stable Time Loop version of this, and Emergency Impersonation, a very similar plot that doesn't require time travel.
- In the tremendously funny Big Finish Doctor Who episode The Kingmaker, William Shakespeare manages to get into a tiff with Richard III through a very complicated time travel mishap, ends up on the Battle of Bosworth Field and promptly gets mistaken for Richard III (very long story) and dies. Once the Doctor is past the initial shock, he wearily realises he's now got to train Richard III in how to be Shakespeare.
- One of the primary plot points in The Ambition of Oda Nobuna, the main character—Yoshiharu Sagara—is deposited in the Sengoku Jidai without warning. Upon his arrival—in the middle of a battlefield—his life is saved by a young soldier, whose actions result in his own death. Asking the man's name, Yoshiharu is startled to discover the man is none other than Toyotomi Hideyoshi. In the aftermath of the battle, he becomes a favorite of Oda Nobuna, and serves has her sandal-bearer, eventually taking Hideyoshi's place in this deviation of history altogether.
- Sengoku Otome has a similar case to Nobuna above. Ordinary High-School Student Hide Yoshino ends up in another world, much resembling the Sengoku Jidai - except everyone in her textbook is a woman. She is found by Oda Nobunaga and Akechi Mitsuhide, introduces herself as Hideyoshi, and ends up taking that role. Turns out her teacher Date-sensei is also in this world, and is currently masquerading as "hick samurai from Oshu" Date Masamune.
- Nobunaga Concerto has high school student Saburou sent back in time and encountering a sickly Oda Nobunaga. When Nobunaga realizes how similar the two look, he asks Saburou to serve as his replacement and later serves him as Akechi Mitsuhide. An interesting depiction, as Saburou was not a particularly good student and only has a vague understanding of history, so the Stable Time Loop is more often than not one that occurs naturally rather than one he deliberately takes.
- Applies to the (Pre-Crisis version of) DC Comics' heroine Superwoman. She was a time traveling researcher who came to the present from the 29th century in order to try to find Superwoman's secret identity, the only superhero whose secrets were never discovered. She ends up realizing that she was supposed to be her. At first she only visited the past when recorded history said Superwoman appeared, but a time travel accident left her stuck there with amnesia for years. She eventually returned to her home time, however.
- This sort of happens in issue #5 of the original run on Fantastic Four, in which Dr. Doom (his first appearance) sends the foursome back in time and The Thing, who has always been a fan of stories of Blackbeard, ends up becoming Blackbeard.
- In the 1930s, Atomic Robo was a fan of pulp novels in general and Westerns in particular - notably, when Jack Tarot shows up, he's engrossed in the story of a bulletproof gunslinger called "Ironhide". When Dr. Dinosaur sets off a "Time Bomb" in The New '10s, he's blown all the way back to The Wild West - and inadvertently becomes the real Ironhide's "successor", despite his best efforts to stay out of history's way.
- In Sword of Slytherin Harry and Draco Malfoy are accidentally sent to the past and end up pretending to be Hogwarts co-founders Salazar Slytherin and Godric Gryffindor, who were killed by bandits.
- In ''My Mirror, Sword, and Shield, Suzaku accidentally travels back in time to the months before the assassination of Emperor Lelouch, gets to know him, and realizes he's actually the demon history makes him out to be... and he ends up inverting this trope by replacing the assassin, saving the emperor, and bringing him back to the future with him.
- In Night Watch, Vimes spends almost the entire novel impersonating his own mentor John Keel, murdered by the other half of the novel's Terminator Twosome.
- In a non-Time Travel example from Mort, Mort and Ysabell learn that the Duke of Sto Helit was supposed to unify and bring peace to the Sto Plains after ascending to the throne via the murder of Queen Keli, an intended future which Mort screwed up by stopping the assassination. By the novel's end, the evil Duke is dead, and Keli appoints Mort as his replacement, obliging him to fulfill the villain's stabilizing role in history, albeit by diplomacy rather than subterfuge or conquest.
- Happens several times in the Time Wars series:
- In The Pimpernel Plot, a time traveller's action causes the death of Sir Percy Blakeney, a.k.a. the Scarlet Pimpernel. One of the Time Commandos is assigned to replace Sir Percy to ensure that the events described in The Scarlet Pimpernel play out as they should. At the end of the mission, another agent is assigned to take over and live out the rest of Sir Percy's life.
- In The Zenda Vendetta, the villains murder Rudolf Rassendyll, again obliging one of the Time Commandos to take his place.
- In The Ivanhoe Gambit, Sir Wilfred of Ivanhoe isn't dead — the heroes deliberately kidnap him so that one of their number can impersonate him as cover — but the timing means that the impersonator does end up having to do all the stuff that Ivanhoe is remembered for (meanwhile, in a subplot, a supporting character becomes King Richard the Lionheart after the real Richard is killed by the villain).
- Perhaps because this imposes a restriction on the plotting, the other Time Wars novels just have the heroes befriending historical figures, not replacing them.
- In Isaac Asimov's The End of Eternity, someone is sent back in time by the leaders of Eternity, a centuries-spanning time-traveling organization, to explain the workings of time travel to its purported inventor, thus completing a Stable Time Loop. The inventor dies, however, and the person from the future ends up replacing him and "inventing" time travel himself. Or rather, this was the plan of the leaders of Eternity, based on secret information about what had happened in the previous iteration of the loop, but in the end of the book the Stable Time Loop gets broken, bringing about the eponymous "End of Eternity". Probably the trope maker, and at minimum the trope codifier: pretty much every other example on this page traces back to Asimov and many directly allude to it.
- In Tim Powers' The Anubis Gates, the main character, expert in the study of a (fictional) Victorian poet, travels back in time and ends up being said poet in the past. This is the variant version mentioned in the description, as the poet in question didn't die and need replacing. He'd always been the time traveller, product of a Stable Time Loop with no discernible origin. Nobody ever composed his poems, either, which worries the protagonist more than the actual replacement does.
- Behold the Man by Michael Moorcock. You can probably figure out the subject in question from the title.
- In one of Poul Anderson's Time Patrol short stories, a time-traveler gets pressed into taking the place of an assassinated Persian royalty; history remembers him as Cyrus the Great.
- Another story in the same series, which has the magnificently awesome title "The Sorrow of Odin the Goth", has a time-travelling anthropologist trying to find the source of a particular legend involving the god Odin. He visits a dark-ages Goth community several times over the course of decades, and the locals, noting that he never seems to age (among other reasons), decide he is Odin. At the end he has to close the Stable Time Loop by doing what Odin is described as doing in the legend, even though it means killing two of his grandsons.
- The variety where the famous person never existed appears in at least two writings of Stanisław Lem.
- The protagonist of Manly Wade Wellman's Twice in Time travels back to Renaissance Florence to meet Leonardo da Vinci and to leave a mark on the back of the Mona Lisa to prove he made the trip. He eventually becomes Leonardo da Vinci and paints the Mona Lisa itself as proof of his trip. Of course, the time traveler's name was Leonard to begin with.
- In The Missing series by Margaret Peterson Haddix, this is combined with Time Travel Escape. A group of children who are adopted, but cannot find their birth parents. They find out they are long lost children of the past (such as Anastasia or Virginia Dare of the Roanoake Colony) that were taken by time travelers from the distant future. Unfortunately, the time machine went wrong and ended up at an airport in the 90s. In the second book, Sent, this trope is almost played straight when Chip and Alex are found to be missing medieval princes who are meant to be killed.
- In The Door into Summer by Robert A. Heinlein, a professor who's invented a faulty form of time travel talks about how one of his students took the risk and went back in time. His name? Leonard Vincent. While he never appears in the story, so we never find out if he really is da Vinci, the protagonist wonders if Leonard, trapped in the past, drew plans for flying machines and such because he was hopelessly trying to recreate things he'd seen in the 20th century. He also quietly mourns for the man, talking about how incredibly impressively difficult it would have been for him to travel across fifteenth century, pre-Columbian America and wrangle his way to Europe, and pitying him as a Fish out of Temporal Water either way.
- The protagonist himself fulfills the trope, first by revolutionizing robotics and then, when he's betrayed by his business partner and fiancee and forced into suspended animation, uses the professor's time travel apparatus to return to the past with knowledge of future designs, set up a rival company, and drive his former partners out of business.
- A Knyght Ther Was had Tom Mallory, a time thief. A particularly nasty rival sabotages his time machine, landing him in the 15th century — when Le Morte d'Arthur was written (or compiled) by Sir Thomas Malory.
- In Dirk Gently's Holistic Detective Agency, it turns out that Johann Sebastian Bach never actually existed; Prof. Chronotis stole some unearthly beautiful music from a Salaxian space ship and used his time machine to plant it in the Baroque era under the pseudonym of Bach.
- In Rokujyouma no Shinryakusha!?, Koutaro is cast in a play based on a legendary knight of Alien Princess Theiamillis' homeworld. Rehearsals include actual fencing lessons because Verisimilitude, bitch! On top of that, the only authentic costume was a full-body-interface Powered Armor used to control her ship. When an attack by one of the princess' rival ends up slinging them both a thousand years into the past to their homeworld, where Koutaro ends up actually becoming the legendary knight.
- A very compacted version happens in Harry Potter and the Prisoner of Azkaban. Harry is swarmed by dementors and sees a figure he believes to be his dead father sending out a patronus to save him. Shortly afterward, Harry and Hermione travel a few hours back in time. Harry makes sure to hide out in the bushes near where the figure appeared so that he can have a chance to actually meet his father. When his father fails to materialize, Harry realizes he must have seen his own time traveling self (who is nearly identical to his father), so he quickly steps out of the bushes and casts the patronus himself, just in time to be seen by his past self and set up (and close off) the Stable Time Loop.
- A key plot point in Babylon 5 involves Sinclair going back in time one thousand years to intervene in the previous war against the Shadows and become the Minbari cultural hero/religious figure Valen in the process.
- Doctor Who:
- "The Myth Makers": Vicki decides to leave the TARDIS when she falls in love with Troilus, becoming the Cressida of Greek mythology.
- "Battlefield": The Seventh Doctor discovers that he will, in his own future, become Merlin in the King Arthur legends.
- The teaser to "Before the Flood" has the Twelfth Doctor directly teach the audience about his trope, although he's specifically using it as an example to teach about the Bootstrap Paradox if Beethoven's work was copied out by a time traveller, who actually wrote the music? The Whoniverse being what it is, as the above examples show, he also has to clarify that it's hypothetical; Beethoven did exist, and the Doctor's met him. ("Nice chap. Very intense. Loved an arm wrestle.")
- "Rosa": A racist time-travelling villain sabotages events to prevent Rosa Parks' pivotal refusal to give up her seat on a segregated bus. Team TARDIS successfully get the bus and its driver back on course, but due to the saboteur, they need three more seats at the front of the bus filled by non-black passengers if Rosa is to be ordered to forfeit her place. With great reluctance, the Doctor, Graham and Yaz fill those seats, substituting for white passengers whom the saboteur had discouraged from boarding.
- Farscape: Aeryn tries this in "Different Destinations" to save the life of a bumbling cook who clearly had no place in a battle. He doesn't let her, though, and dies like he's "supposed" to. Still doesn't fix the timeline, though...
- In the final season episode "Mokey Then and Now" of Fraggle Rock, Mokey, Wembley, and Boober accidentally get sent back in time after triggering some mysterious magic. They're sent back to a time in the distant past that Mokey identified as being before the arrival of a figure called the Great and Wondrous Blunding. It turns out that the Great and Wondrous Blunding was none other than Mokey Fraggle, who teaches the ancient Fraggles the "Dance Your Cares Away" song, promotes having hair, and encourages freedom over following a leader.
- In Heroes, Hiro goes to 17th century Japan to find that his childhood idol, Takezo Kensei, doesn't even come close to meeting his expectations. While not actually doing (some of) the amazing things that Kensei would be credited for, Hiro definitely plays a part in the making of history. In fact, the writers actually try and fake out the audience to think this is what Hiro is going to do after Kensei dies. However it is revealed shortly afterward that he is a "Special" and his wounds heal.
- Legends of Tomorrow:
- In "Abominations", a Union messenger crucial to Ulysses Grant's victory in the Vicksburg campaign gets killed by zombies. So Jax has to take his place (and his name) to deliver a set of stolen battle plans to Grant.
- In "Camelot/3000" this trope occurs twice. First, the wizard Merlin turns out to be Stargirl. Then at the end of the episode, Queen Guinevere refers to Sara as "Sara Lance-a-lot", which sounds an awful lot like "Sir Lancelot".
- The Ministry of Time: Rogelio Buendía in episode 9. After accidentally getting El Cid killed in 1079 while he filmed him fighting, he takes over his life, spending twenty years without seeing his family and playing someone he is not, even dying when the historical Cid did. Doubles as Heroic Sacrifice.
- There is some Fridge Brilliance here in that Buendía is a Francoist-era soldier (in fact, he was filming El Cid as documentation for the semi-propagandistic 1961 film starring Charlton Heston) and the Cid he tries to live as is the legendary one that appears in the Medieval epics, rather than the purely historical one, because he knows no better. As a result, the legendary Cid ultimately arises from Buendía's own actions, rather than their supposed historical inspiration.
- In Red Dwarf, the crew go back in time and accidentally kill Lee Harvey Oswald, preventing the Kennedy assassination. After the usual time travel shenanigans, eventually they convince a JFK from later in the time line to take the place of the assassin, firing from the grassy knoll.
- Star Trek:
- In the Star Trek: Deep Space Nine two-parter "Past Tense", Sisko ends up in the 21st century as the result of a transporter accident, where he has to impersonate the soon-to-be martyr Gabriel Bell after accidentally causing his death in a food line. At the end of the episode Starfleet Command has some questions to ask about why the picture of Gabriel Bell in the history books resembles him so closely; it gets Lampshaded again in a later episode when Nog is looking at a historical database and comments that Gabriel Bell looks an awful lot like Sisko.
- In an early draft of the Star Trek: The Next Generation episode "Yesterday's Enterprise", Surak was accidentally killed by time-travelers, and Sarek had to take his place in order to bring logic to Vulcan. The actual episode is a borderline example. Tasha ends up going back in time with the Enterprise-C after she dies, but it's not to fool anyone into thinking she's anyone important — it's just that they need somebody to manage tactical station on the ship.
- Deep Space Nine also has a strange example with a short timeframe. In "Visionary", O'Brien is time-jumping uncontrollably, and he sees the station blow up in the future. To prevent this, he decides to force a time-jump, find out how the disaster happens, and come back. Unfortunately, the device that makes this possible emits deadly radiation, and O'Brien overestimates his endurance; when it's time to go back, he realizes he won't survive the return trip. Solution? He gives his future self the device and sends him back. The disaster is averted, and at the end of the day there's still just one O'Brien, but he can't help wondering if he's really the same man.
- A common element in Timeless. The premise is that a team of time travelers must prevent a rogue time traveler from rewriting history. Before they manage to foil the evil plan each episode, the bad guy has usually killed off an important historical figure or otherwise interfered with the historical event, so the team must undo the changes as best they can. When they return to the present, the new version of history incorporates their interventions.
- The Twilight Zone (1985):
- In "Profile in Silver", Professor Joseph Fitzgerald, a time traveler from 2172, travels back in time and ends up saving his Famous Ancestor John F. Kennedy from the assassin's bullet. As a result, this creates an Alternate Timeline where the extinction of the human race via nuclear war or other equally grim possibilities is inevitable. Kennedy is informed of this and offers to go back to be assassinated in order to restore the timeline, only for Fitzgerald to send him to the future instead while he takes Kennedy's place in the limo and dies. In 2172, Kennedy gives a lecture at Harvard praising the sacrifice of heroes like Fitzgerad.
- In "The Once and Future King", the Elvis Impersonator Gary Pitkin is sent back in time to Memphis, Tennessee on July 3, 1954 and meets the real Elvis Presley, two days before he is due to perform "That's All Right" for Sam Phillips at Sun Records. The next day, Gary learns that Elvis intends to play "I Love You Because" instead and tries to convince him that he will ruin his chances of a record deal if he does so. However, Elvis begins to suspect that Gary has been sent to tempt him with devil's music and attacks him. In the ensuing fight, Elvis is impaled on the neck of his guitar and dies. Gary then assumes his identity and performs "That's All Right" for Phillips as history records Elvis did. It turns out that it was Gary posing as Elvis rather than the real Elvis who was destined to become the King of Rock & Roll. However, Gary wonders if Elvis would have made a better King if he had lived.
- There's a TV-movie (read: Poorly Disguised Pilot) that involves a NY cop being hunted by time-travellers from the past, to prevent him from realising his destiny — to go back in time to become... wait for it... Nostradamus. Unlike most examples, the Stable Time Loop is averted, except for a woman with Ripple Effect-Proof Memory.
- The Thespians in Continuum have this as a big part of their schtick. The subject doesn't necessarily have to be dead, either, just unavailable for their historic moment.
- In Gamelet, a currently-in-development video game, you play a time traveler who ends up having to act out the plot of Hamlet, impersonating the title character.
- Jigsaw forces you to be the instigator of some of the twentieth century's worst disasters, starting with assassinating Archduke Franz Ferdinand. You end up doing as much good as harm, though.
- Subnormality: One strip is all about a time travelling paladin sent back in time to 'congratulate' his order's founding prophet on creating a successful religion, and then send a time capsule containing the autobiography of the prophet. He's too indoctrinated to realize how spreading the word about the coming prophet would make him the prophet until someone from the local time period asks for his autobiography.
- In Family Guy, Stewie discovers Leonardo da Vinci was his ancestor, and his archnemesis travels back in time to kill him, therefore eliminating Stewie's existence. In the end, Leo dies, so Stewie must continue living in the 16th Century as him until he can pass his progeny forward, after that, he built a cryogeny chamber and froze himself until the present day.
- In Futurama, Fry travels back in time and accidentally kills his own grandfather before his father could be conceived. When Fry doesn't cease to exist, he correctly assumes the man he thought was his grandfather wasn't really his grandfather. He then incorrectly assumes the woman he thought was his grandmother isn't either, and sleeps with her. Afterward, his friends have to explain to him that in doing so, he effectively became his own grandfather.