"The Destiny Trap: you can't change history if you're part of it."
— The Eleventh Doctor, Doctor Who, "The Time of the Doctor"
Also known as a predestination paradox.
Through Applied Phlebotinum, Functional Magic, or some other means, our heroes travel back to the past. In the past, they wind up being responsible for the very events that underpin their own "present." This creates a chicken-and-egg scenario, in which the looping sequence of events has no clear beginning. The result of breaking the zeroth law of Time Travel: do not cause the event you went back to prevent.
This is also the basic premise of how Time Travel would work, according to Albert Einstein. Simply put, even if it were possible to travel back in time, you would not be able to change any events in the past, because they've already happened. No matter what your intentions, everything that you did would only fulfill the past. The only thing that would change is your perception of the events. (Thus explaining Hitler's Time Travel Exemption Act.)
This is sometimes referred to as a "time loop" paradox, particularly when a character, object, or piece of information was never originally created, but exists solely because of its own existence. Also known as a "bootstrap paradox," from the classic Heinlein short story, By His Bootstraps. It's also called a "Temporal Paradox" or "ontological paradox". The classic hypothetical example is to jump into the future, steal some wondrous gadget, come back to the original time, grab the patent on that gadget and start mass-producing them immediately. Eventually, they become so ubiquitous or so common that you, ten, twenty years younger, show up and steal one. The simplest version is the one where the time machine itself is the product of the stable time loop — the character sees a version of himself pop into existence with a time machine, hand it to him, and press the button, only to be whisked into the past where he hands it to his past self and presses the button.
Tricked Out Time is when you "change" the past on purpose to resemble this. Compare You Already Changed The Past, which often results in this. A Wayback Trip usually implies this. If this occurs in a universe where you can Set Right What Once Went Wrong, you most likely have a Timey-Wimey Ball on your hands. See Retroactive Preparation for one way this can be exploited. For the Recursive Fiction variant of this, see Mutually Fictional.
Since many examples of this trope aren't revealed until late in the story, and the existence of a loop can itself be a spoiler, consider yourself spoiler-warned.
This trope is not to be confused with "Groundhog Day" Loop.
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Anime and Manga
In Simoun, Dominura and Limone travel back in time using the Emerald Ri Maajon, purportedly to stop Simulacrum from using the Simoun. To avoid a Temporal Paradox that would prevent them from meeting, however, they instead teach the very Emerald Ri Maajon that got them there to the local inhabitants and show them how to use the Simoun that they have lying around... thereby ensuring that history unfolds exactly as they remember.
In El-Hazard: The Magnificent World, the main character and company are sent to El Hazard by Ifurita. They meet her in El Hazard, but as an enemy who doesn't remember them. After a Heel-Face Turn, Ifurita rescues everyone from a time-space distortion weapon, and realizes that she must be caught in it in order to go back in time in order to start everything. The final scene shows that the loop also involves an older Makoto returning to Earth to reunite with Ifurita. Unfortunately, the sequels were so poorly-received that we never got to see how the loop is completed.
Takahashi's Fire Tripper one-shot story (in some ways a dry run for InuYasha), avoids the trope almost completely. One can trace the time lines of both characters, and they never "loop" themselves. There is one small loop though that leads to a Fridge Logic moment after the show is over. Where did the bell come from?
Mendo from Urusei Yatsura traveled to the past to try to prevent himself from acquiring his fear of darkness and cramped spaces, but he got so angry at his younger self that he ended up attacking his younger self and thereby causing his own phobias.
In Martian Successor Nadesico, Inez Fressange, whose first clear memory is being lost in a desert at age 8, discovers that she got there through time traveling from the future... which is now the present, as she's taken The Slow Path back. She meets her younger self just before the temporal disturbance that triggers the loop.
In Tenchi Muyo! in Love!, the criminal Kain attempts to go back in time to kill Tenchi's mother, Achika, so as to prevent Tenchi from ever having been born. Tenchi and company go back in time to stop him, and the climactic showdown forces Achika to utilize her power to the point that she shortens her own lifespan in order to protect her future son, thus causing her premature death that Tenchi had already experienced in the present/future.
In the 3rd OVA series, Tsunami, Washu and Tokimi agree on letting history play out normally and let Tenchi grow into his godhood normally. Thus, history is reset and events play out normally up until the point Ryoko goes to drag Mihoshi to breakfast the morning Tenchi's sister arrives. Mihoshi makes sure that her original message gets sent through, but Noike, wanting to be with Tenchi (and ensuring the events of Tenchi Muyo GXP happens), makes sure the altered note gets set instead and the Chobimaru is launched.
HOWEVER, the presence of the big bad, Z, is averted.
During the (rather long) Day 1 of the Mahora Fair sub-arc in Mahou Sensei Negima! we get to see a Time Loop following Negi's use of it. Negi redoes the same day four times to make sure he has enough time to spend with every student. At various points Negi will run into students he hasn't run into yet because he's not that far in the loop. Setsuna, Asuna, Konoka and Kotaro all go along with Negi at one time or another in this loop. Naturally when Time Travel isn't a neat parlor trick it stops being so stable... or loop like, and quite wibbly-wobbly.
In Sailor Moon, Chibi-Usa is able to exist because she "stole" the silver crystal from Usagi in the future, returned to the past, and saved Usagi's life in the battle with the Death Phantom.
In Tsubasa Reservoir Chronicle — avoiding spoilers and the five paragraphs of text that it would require to fully explain it — something the main characters do halfway through the story is directly responsible for the creation of the lead female's hometown as we first saw it.
Later combined with reincarnation, parallel universes, and cloning to induce an extreme My Own Grampa scenario.
Dragon Ball — Kami-Sama sends Kid Goku back in time to help his future instructor Roshi.
Freeza had the Saiyans wiped out due to his growing fear that they would overthrow him, with the legend of the "Super Saiyan" being a key part of said fear. Episode of Bardock shows that when Goku's father Bardock was hit by Freeza's Death Ball that destroyed Planet Vegeta, he was somehow thrown into the past. There he defeats Freeza's ancestor Chilled, going Super Saiyan in the process, thus creating the very legend that led to the genocide of the Saiyans and Bardock being sent to the past. Of course, Episode of Bardock's status as canon is up in the air and heavily contested.
In Natsu no Arashi!, Kaya's diary was lost sixty years ago. So, Arashi time-leaps back to 60 years ago, grabs the diary from before it was lost, and brings it to the present. Which, as Hajime immediately explains, is why it went missing in the first place.
When the heroes of Rave Master reach what was once the Kingdom of Symphonia they discover, along with the grave of Resha Valentine, a skeleton wearing a necklace identical to one Elie was wearing, complete with engraving, that she had purchased from a store. Many volumes later, characters go back in time. Elie lost her necklace while in the past. Also, Sieg Hart sent Haru and Elie back to the present but is forced to remain in the past himself. This is when Sieg realizes that he was the skeleton they found back then. That knowledge in mind, he takes first opportunity to snag the necklace back and puts himself into position to be found fifty years later.
In the Bamboo Rhapsody episode of Haruhi Suzumiya, Kyon travels back 3 years and ends up being the cause of Haruhi attending his highschool. When Kyon complains that this contradicts Mikuru's explanation of Time Travel, a sufficiently-advanced Yuki brushes it off with, "since there's no conclusion to the paradox theory, there's no way to prove there's no paradox." It gets tied in knots in The Disappearance of Suzumiya Haruhi, where we see that three copies of Kyon and Mikuru actually exist at the same time for a brief period on December 18 (and Kyon actually memorizes the words he heard from his future self, to later tell them to his past self). Mikuru is the embodiment of stable time loops anyway; an entire book is dedicated to her walking around with Kyon triggering key events for her future. This phenomenon pisses off the anti-Mikuru, "Sneering Bastard," to no end; he hates that You Can't Fight Fate.
When Kyon first meets Future Mikuru, she tries to prove her identity by showing him a star-shaped mole on her breast. When he freaks out and exclaims that he doesn't have any idea if his Mikuru has anything like that, the future version is confused. After all, he's the one who told her about it, and she didn't even know she had it before...oh.
In Mx0, Taiga fails to get into Senaigi because when he is asked "what would you do if magic were real?" and he answers (for reasons he doesn't understand) "Conquer the world." This causes a girl to laugh at him. After steaming over it all summer he decides to confront the girl at Senaigi, where he's mistaken for a student and ushered into the school. Once the faculty find this out, they decide to give him a chance at staying at the school to save their own face. They then send him back in time (possessing his own body rather than existing twice at one time) and tell him to read the invisible words on the final page of his interview book and he'll automatically pass. However, the book is lost and then found by his older sister who rushes it to him, but not before meeting her idol. She asks him for an autograph, but has no paper, so he signs the seemingly blank last page with the words "Conquer the world!"
During the Great War in Kyo Kara Maoh, Suzanna Julia doesn't fully accept that she's going to die and that her soul is to become the next Maoh. So, to convince her, what does Shinou do? SEND HER YUURI, OF COURSE. Yuuri's presence in the past makes Julia finally accept her fate, and in turn makes it possible for him to exist as Maoh in the future.
Yuki Saiko of Silent Mobius has a mysteriously great deal on renting her apartment and cafe (in Tokyo, no less). Then she gets sent back in time to 1999 before the Project Gaia catastrophe and meets a young man named Tohru and the two fall in love. It turns out that he grows up to be her landlord. The TV series also hints that he has something to do with the Tyke Bomb project that produced her.
Lupin III Elusiveness Of The Fog is Mamo Kyosuke's revenge against Lupin, for trying to kill him as he builds a time machine. He's from the far-flung future, bearing a grudge against the Lupin family. Originally, he just wanted to kill Lupin III, but when he was testing his time-machine, he saw a rock vanish before his eyes, proving that it had been erased sometime before the future. Because he had planned to chase after Lupin, he assumed that Lupin somehow managed to steal his time machine and made the rock vanish. So he sent Lupin III from the present, to the far past. Turns out, while he was trying to kill Lupin (in the past), he accidentally blew up the rock, making it vanish (in the future), and in the process, causing himself to freak out and go to the present...
When Geronimo goes through a trial to become a true Chojin, he enters a canyon where he and his sister got lost as children, but were saved by a mysterious stranger. While he's there, he finds another little boy and girl who've gotten lost, whom he saves. After saving them, he realizes that he was the mysterious stranger, sent back in time to save himself and his sister via STL.
This almost happened in Seikimatsu Occult Gakuin since it turns out Fumiaki accidentally meeting his younger self is what triggered the alien apocalypse in the first place. The one Fumiaki was sent back in time to avert. Fumiaki manages to Screw Destiny using his reawakened psychic powers to save the world, sacrificing himself in the process.
Doraemon is fond of this. Many time the titular character and Nobita time-travel to fix an event in the past only to find out that they are actually the culprit of what they are trying to fix.
In a heartwarming example, in an episode that Doraemon and Nobita goes back in time to help his father decides to continue pursuing his artist carrier which almost resulted in Nobita ceases to exist as his father not married Tamako but Kaneko instead. Fortunately, he refused to marry her and met Tamako which ensured Nobita's existance.
In Gall Force, the spacecraft used to evacuate the last surviving humans and yumans in New Era bears a striking resemblance to the one shown in historical records showing the original colonization of the solnoid homeworld in Stardust War, which suggests that the humans, yumans, MME, solnoids, and paranoids may all be each other's ancestors.
After being sent back in time in the third Fairy TailOVA, Lucy saves the life of herself as a child. Her past-self is inspired by Lucy's Fairy Tail tattoo to join Fairy Tail. Natsu gets disgusted by his past-self and beats him up, creating the scar on his neck. The magic book that brought them to the past is left behind, and the past-Makarov finds it and stores it in the archives, where the protagonists found it in the beginning.
Viewtiful Joe once stole his own cheeseburger through this method.
The sundial watch in Jinrui wa Suitai Shimashita seems to exist in one: "Watashi" gets it from her grandfather he says he got it from a pretty lady that wasn't her grandmother. Then Watashi gets sent back in time, where an annoying brat steals it from her...
Kamisama Kiss has Nanami traveling back five hundred years to Feudal Japan to save a Little Bit BeastlyKitsune, Tomoe, that she has fallen in love with from a curse. Turns out she is the one who saved a wounded Tomoe from the village militia, not Tomoe's first love Yukiji, and that she is directly responsible for Tomoe falling in love with "Yukiji" to begin with. Not to mention the catalyst that past!Tomoe used for the spell to turn him into human was actually the hair pin present!Tomoe gave Nanami and she had brought it along with her into the past. And this is the original event that sets all other parts of Nanami and Tomoe's story in motion.
On the side note, the reason Mikage gave Nanami his position as the Land God was because he had met future!Nanami and knew what he needed to do from her, which lead to him leaving the shrine for decades.
Actually invoked in The World God Only Knows. Dokuro Skull knew that there were so many powerful enemies trying to destroy New Hell (and by extension, Earth and Heaven) that their chances of survival were astronomically small. So she constructed a beacon device that could be used to communicate with the future. Once the future version of the device determined that they had survived the catastrophe, it would send someone back in time, where he could ensure that this good future came to pass.
In Date A Live Origami killed her own parents when she travel back in time tried to stop Phantom killing her parents(which it didn't)
Maybe the best example is given by Universal War One: the whole plot is based on not one, not two but three nested stable loops, without any Plot Hole.
Subverted in Calvin and Hobbes. It's 6:30 and Calvin doesn't want to do his homework, so he decides to Time Travel forward to 8:30. Then he can pick up the now-finished homework, bring it back to 6:30, and goof off the rest of the evening. But it doesn't work. There's no homework to pick up at 8:30 because Calvin never actually did the homework — he went time traveling instead.
The best part came, of course, when they BOTH decided to go after 7:30 Calvin, because he was the one who was supposed to be doing it. That didn't work either.
In The Invisibles, Gideon is introduced to The Invisible College by an elderly Edith Manning, who recognises him as a time traveller from her youth. After entering the college, he is taught to Time Travel, which results in him going back and meeting her as a young woman...
The elves in ElfQuest are only on the planet because their alien ancestors ("the coneheads," later termed "the High Ones") were attracted by the human tales of elven beings. The coneheads shapeshifted into elven beings and turned their spacecraft into a palace, then, as they were landing, were flung back to the caveman days, where all their powers stopped working and they were nearly killed. The few survivors founded some cultures that became the elves that begat the stories that prompted the coneheads to attempt to land in the first place.
Later on, the magic-user Rayek attempts to stop the event that flung the High Ones into the past. It's pointed out that those who were born as a result of this event would cease to exist should he succeed, but he doesn't care (except, it seems, for the few he knows personally). He's talked out of it by the three people most dear to him, who choose to suffer the same fate as the planet; as Rayek can't bring himself to erase them, he stands aside and lets the event happen as it already has.
His plan, more specifically, was to merge the two magical spaceships (the actual one and the one that took The Slow Path for 10000 years) and prevent the time loop by making the spaceship stable through the power of applied Object Paradox.
In the Elseworlds book Superman: Red Son, it's revealed that Superman was sent back in time as a baby, because Lex Luthor was the ancestor of Jor-L, and therefore Krypton is actually Earth in the future. That might explain why the Red Son-verse doesn't have Kryptonite.
Ironic in that Jor-L sends his son to the past, as opposed to another planet, because he dislikes how placid humanity has become. Humans think they've learned all there is to learn and now just "have nothing left to do but wait and die". Jor-L hopes that sending his son to the past will change that. However, the antagonism between Superman and Lex Luthor is what inspires Luthorto engineer the Golden Age Jor-L hopes to avert.
In one story, Superman is shown a vision of the future, and sees a superhero codenamed Sirocco (which means The Desert Wind in Persian). Later, when Superman visits Iran and befriends Sirocco's present self, he accidentally calls him by that name. The man says the name is cool and asks Supes if he can use it for his codename.
The original Legion of Super-Heroes seems to be an example of this—they were inspired by Superboy, and they make him a member and have him fight alongside them, arguably shaping him into the hero who inspired them.
The final pages of Ultimate Fantastic Four #53 show that Reed sends his Cosmic Cube back in time 30,000 years to the planet Acheron, where Thanos finds it, which precipitated his rise; when he lost it, he influenced Reed to create it.
In Tales From The Bully Pulpit, Teddy Roosevelt gets help from the "Teddy of thirty minutes from now" (a reference to the Bill & Ted example below). At the end of the story, the main characters remember to go back and fulfill the time loop before going off on their adventures.
In Amazing Spider-Man Annual #20, Arno Stark, the Iron Man of 2020, has developed a time machine that received military backing by an atomic bomb project that he is also developing. An anti-war terrorist locks up Iron Man's wife and son in the laboratory which contains the bomb, but is killed by Arno soon afterward. To defuse the bomb, Arno uses his time machine to go back to the 1980s to get the terrorist's retina patterns. In doing so, though, Iron Man becomes involved in a fight with Spider-Man which results in the child becoming scarred — giving him the motivation against Iron Man in the first place. It gets worse... Not only did Arno not get the retina scan he needed (the scanner was destroyed in the fight), he is suddenly returned to the future, only to discover that the bomb had detonated prematurely and killed his family.
Alan Moore's Supreme has two stable time loops, one forming the main plot of the initial plot arc, and a second in a single issue as a comic parody of the trope. It's strongly implied that the mysterious "Supremium" substance that both originally gave Supreme his powers and acts as his "Kryptonite" is what all time-looped matter eventually becomes.
52 has two of them in the Booster Gold plot line. One of them has Booster fake his death and then travel back in time a few weeks so he can become Supernova and drive Booster to the actions which lead him into the Loop. The other has Booster send Mister Mind back through time after forcing him back into his larval form, to the point where he was discovered by Doctor Sivana who imprisoned him until he was forced to infect Skeets, starting the loop over. Both were created due to the actions of Rip Hunter.
Rip Hunter himself is also a stable time loop: he reveals that he's Booster Gold's son, who only will come into being because Rip Hunter drafts Booster Gold into his current job as secret protector of the timeline.
Best one ever: The whole reason for Imperiex's existence during Our Worlds At War is that the multiverse is flawed, so he seeks to destroy everything to re-create it. As a force of nature, he can't be destroyed: to wit, when he seems defeated, his energy was merely absorbed by Brainiac, who then starts a plan to assimilate the universe with that power. Superman has a huge problem: If he destroys Brainiac, Imperiex gets free and can "hollow" the multiverse. But if he leaves Brainiac be, the multiverse will be assimilated. What does Superman do? He arranges for a Time portal to be opened and pushes Brainiac/Imperiex (who are the size of a PLANET) into it, taking them to... a milisecond after the Big Bang. Their essences get in the way of nature, forming our flawed multiverse instead of the "perfect" one that should have been, but making sure that neither is a problem from there on out in the present. Imperiex thus gets to realize the irony of its entire existence the instant before his "death".
Flash: Rebirth has used this to retcon the origin of the Flash's powers. That lightning bolt that struck Barry in the first place? Caused by his future self and successor, stopping a psychopath speedster from killing Barry's Love Interest in the past.
One Silver Age Superman story featured Kristen Wells, a researcher from the future who traveled back in time to find out who the mysterious superhero "Superwoman" was. Unable to find her anywhere, she eventually realizes it was she herself, so she puts on the Superwoman costume and uses future technology to do all the superheroic feats that future history books claim Superwoman did.
In The New Universe, it is revealed that the Old Man is an older Ken Connell, who was thrown back in time and, thanks to the power of the Star Brand, lived for centuries before accidentally initiating the White Event and giving his younger self the Brand.
One Radioactive Man comic from the 1960s features a villain being sent back to the 1860s via a Trans-spatial Stair Climber. When a damaged robot appears out of thin air, he repairs it and programs it to kill Radioactive Man before placing it in a time capsule due to be opened in 100 years time. At the end of the comic, the robot is damaged by Radioactive Man before being hit by Dr. Broom's Time Machine Gun — and sent back to 1863. When Fallout Boy wonders about who built the robot in the first place, Radioactive Man reminds him that "we were dealing with two renegade scientists tampering with time travel, and that's a pair o' docs better left alone."
The Uncle Scrooge story, "Of Ducks, Dimes, and Destinies," features Scrooge's nemesis Magica DeSpell travelling back in time to steal Scrooge's legendary number one dime. The man who was supposed to pay Scrooge the dime for a shoeshine decides to go out for a drink after Scrooge passes out shining his ridiculously muddy shoes. Magica intercepts the man and steals the dime, only to realize that since she stole it before it was given to Scrooge, it is no longer the first coin earned by the world's richest man (the last component she needs for a spell to create an amulet that can turn things into gold). Magica winds up giving the dime to an unconscious Scrooge, completing the loop.
She-Hulk once dealt with a rather complicated one for her law firm. The case: A billionaire named Charles Czarkowski shot an unarmed man (dubbed "John Doe"), in the back, in broad daylight, in front of a dozen eye-witnesses, and it was caught on film. Czarkowski claimed that before the shooting he received a message from the future warning that John Doe was destined to shoot him, and Czarkowski shot him in self-defense. Fearing for his life when a time-robot attacked the courtroom, Czarkowski traveled through time, used a DNA scrambler to alter his appearance, and tried to send a message back in time to warn his past self. But when he saw his altered face in the mirror he realized that he was John Doe all along. The message he sent to warn himself accidentally implicated his future self in the murder of his past self. Then the Time Variance Authority showed up and forced Czarkowski to go back in time again and get shot to maintain the time loop. On the plus side, the TVA had to drop the attempted murder charge against him.
Robo finds himself in one of these in Atomic Robo and the Shadow from Beyond Time, where three future versions of Robo instruct him to learn the hell out of hyperdimensional mathematics so he can return to that point in time-space to defeat the Eldritch Abomination they're fighting. It's not a true Stable Time Loop, of course, because Robo is very insistent that there's no such thing as time travel.
When Sonic the Comic did an adaptation of Sonic the Hedgehog CD (a game where time travel is one of the main mechanics), it pulled off a loop so neat that, in the last part of the story, they could reprint an unedited page from an earlier issue and have it make perfect sense and not seem like laziness on the part of the writer or artist. (The first time the page appeared, the audience perspective is that of present Sonic; the second time, we're following future Sonic, who's been shrunk.)
In H-E-R-O, this is the fate of the HERO dial. At the end of the series, it gets thrown back in time, where it's found by its very first user, who featured in a Whole Episode Flashback earlier in the series.
Thor's grandfather, Bor, was defeated in battle against Frost Giants. He did not expect them to use magic, and therefore wasn't protected when a sorcerer cursed him and turned him into living snow. He told his son, Odin, to find a stronger sorcerer and undo the curse, but Odin stalled for years. When Thor was born, Odin noticed he had Bor's eyes, and was ridden with guilt when Bor's spirit came to him and told him he'd be forgiven if he adopts a child whose father he'd kill in his next war. As it happens, Odin's next war was against Frost Giants as well, and the child whose father he killed was Loki. Thus was Loki adopted as an Asgardian. The truth is Loki was the sorcerer who turned Bor into living snow. He returned back in time to do that, and then he appeared to Odin as Bor's spirit and told him to adopt the child. Then he went to his younger self and instructed him exactly what to do and say so to incite war between the Frost Giants and the Asgardians, so he'd be adopted as an Asgardian and become the man he's today.
Journey into Mystery brings us a whole new one, once again involving Loki. The reincarnated Kid Loki meets Leah as Hela's handmaiden. He proceeds to write a character based on her into the past of the Serpent. Later, Hela's hand is healed, Leah (having been Hela's literal handmaiden) disappears, and Hela makes a cryptic comment to Loki about how everyone believes he is her father. When Surtur tries to burn the Nine Realms he recruits the girl Loki wrote into the Serpent's past, as she resents Loki for not giving her any chance to grow. Loki rewrites the girl's story so that she becomes the Leah that he knew. Then things happen in such a way that he ends up asking Hela to send the new Leah to a place as far away from him as possible. Hela sends Leah to the distant past, and reveals to the readers that she is Leah, all grown up.
In a Thunderbolts storyline, the team was sent back in time, encountering the original group, back when they were still villains posing as heroes. Fixer's past self learns of his future, decides he's a total loser, and tries to change things. Fixer tries to stop him, inadvertently killing him. This, along with the present T-Bolt's base being in the past too long, results in the unraveling of time. In order to fix things, Fixer has his appearance and DNA altered so he looks just like his young self, and stays in the past. The past Thunderbolts' memories are erased (including Fixer's), and the present Thunderbolts return home. Songbird points out at one point that Fixer is now fated to go round and round in time, forever more.
The climax of the Doctor Who Magazine comic strip "The Burning Stone" strongly implies that the imprinting of the TARDIS on the human psyche influenced the design of the London Metropolitan Police Box.
In X-Factor it is revealed that the origins of Longshot and Shatterstar, two characters from different centuries in the Mojoverse, work this way. During a battle, the demon lord Mephisto blasted Shatterstar into the Mojoverse's past. There he was studied by the scientist Arize, who used his genes to create Longshot. Many years later, Longshot would marry Dazzler, a human mutant and father a child with her — Shatterstar himself. The time-traveling Shatterstar took his infant self, and erased Dazzler and Longshot's memories of his birth. He and his partner Rictor then took the infant a century into the future to be raised as a gladiator and play out Shatterstar's life as he remembered it.
It is notable that this is not the first instance of this occurring in the Mojoverse, as a human stuntwoman from Earth, "Ricochet" Rita Wayword, is turned into the warrior-sorceressSpiral in the Mojoverse's future and then sent back into the past to serve an earlier version of Mojo and ultimately facilitate her own transformation into Spiral. Unlike many other dimensions in the Marvel Universe, the Mojoverse does not spawn alternate timelines easily (because it's a "pocket dimension" that's directly tied to the main Marvel Universe; most alternative timelines have their own attached Mojoverse), making such stable time loops possible there.
My Little Pony: Friendship Is Magic has ''Que Sera, Sera''. Celestia's ability to know the future is finally explained after she summons Twilight Sparkle and her friends to defeat a great foe — an ancient dragon who has awoken and gone on a rampage, but Celestia knows that it is all according to plan — and indeed, the rampage was a collaboration between the dragon and Princess Celestia, without even Princess Luna's knowledge. The reason is that the dragon is Spike, several thousand years older, and he uses his firey breath to send himself and the Mane Six back over two thousand years into the past. Twilight at first worries about changing the future, but eventually realizes that they are permanently stuck in the past and relaxes. Eventually she has two children, naming one of them after Celestia, and the other after Trixie, though her sister mispronounces Lulumoon as "Luna-moon". When Discord shows up, she and the rest of the mane six expect the princesses to show up... but they don't, because they're still foals. Namely, Twilight's. And the Elements of Harmony don't even exist yet, the only weapon that can beat Discord. Or at least, they don't exist in the form of the elements... In the end, Twilight and her friends have to sacrifice themselves and BECOME the Elements of Harmony, entrusting Spike to help Luna and Celestia, and then eventually become the monster that sends them into the past in the first place, several thousand years down the line. The story ends with Spike having reverted to his child-like form and finally reuniting with Celestia, who has just had to send her own mother to her death.
Harry Potter and the Methods of Rationality has four of these to date, the most notable one being when Harry pulled a prank on himself using a Time Turner, an Invisibility Cloak, two pies, and several sheets of parchment.
His attempt to use Time Loop Logic (see Real Life below) as a manually-performed perfect algorithm was... less than successful. The output: DO NOT MESS WITH TIME
Kyon Big Damn Hero has these every few chapters, and so many that any unresolved ones are offering Kyon protection from the IDSE. As soon as he resolves the last one...
Yabba Dabba Joes — Destro went through almost three dozen agents trying to kill members of the Joe team in their cribs before finally accepting that time travel in the Joe-verse doesn't allow changing the past.
Paradox has a stable time loop despite the name. Shampoo strands Ukyou and Ryouga in the past, where they become the real parents of Ranma who is stolen at birth by Genma.
One Harry Potter fanfic had a four year old Harry being sent back in time to when his parents were newly married. In the end Harry gets sent back to the present, completely forgetting everything that happened. Meanwhile in the past, Sirius convinces James to make Peter his and Lily's secret keeper so they won't be killed and the future Harry came from will never be. ...yeah.
In another Harry Potter comedy (Harry Potter and the Sword of Gryffindor by cloneserpents), Hermione steals a time turner for the purposes of "kinky sex" that will also hurt Death Eaters. This is explained by Hermione at the time saying that she sort-of got it through a time paradox, but not to worry about it. Later, Harry is sent to put it back in the Department of Mysteries at the same time as stealing it in the first place. On the way, he runs into Mad-Eye Moody, who says that the DoM is being guarded after the events of Harry Potter and the Order of the Phoenix and that he should probably not venture in there. Upon exiting in failure, Hermione suggests that he just give her the one that he had to put back. This leads to Harry having a Logic Bomb moment along the lines of "But you gave this to me after traveling through time... and I just gave it to you... where did it come from?!"
The Marvel-verse fanfic Dreams of the Waking Manis all about one giant stable time-loop. In the far future, Deadpool helps Cable and Hope to return to the present, which causes a chain of events that influences the entire Marvel universe and ensures Deadpool will always be in the Future to help Cable and Hope to get back to the present.
The Evangelion fanfic Matters of Faith Sets one up with the Angel Lelial, sending Shinji and Unit-01 back in time to the Big Bang, and reveals that ADAM is actually Shinji and Unit-01 in the Berserker Mode.
The Buzz Lightyear of Star Command fic One Hundred Dayshappens because one long time-loop. Warp's canonical death-stunt sets up Buzz and Mira to work together as teammates, thus giving them the opportunity to know each other very well. Then, Warp's revelation of his parenthood drives the pair to marry and avoid a scandal, thus allowing him to be born in the first place. At some undefined point in the future, Buzz and Mira send a baby Warp back through time (the how remains unexplained) and close the loop, as remembered by Warp in the climax.
The entire premise of the Facing The Future Series is dependent on one of these. When Future Danny and Sam travel back in time to fight Dark Danny, present day Sam is driven by the revelation that her future self is half ghost to gain ghost powers of her own, thus becoming Danny's new partner.
The Pony POV Series has a rather complex one show up in the sub-arc following the conclusion of Dark World: When Twilight/Amicitia ascends, Cadence warns her that her greatest enemy awaits at the dawn of time. So she goes back then, where Mortis warns her that they're destined to one day fight each other as well, before helping her evade a sneak attack from a younger Cadence, who's convinced that magic is inherently evil and wants to kill Amicitia to prevent its existence. After Amicitia barely defeats her, she then hops back in time a bit and tells Mortis to warn her, before going on to traverse her own timeline to be the Benevolent Interloper and shield her mortal self from Nightmare Eclipse/Paradox's influence, thus insuring her own existence. And then she makes sure Razzaroo's Apocalyptic Log survives G3's Cosmic Retcon and sends it to the spirit world, where Razzaroo would then use it to nearly become The Magician Alicorn and challenge Dark World Twilight for the spot in the first place. Notably, Mortis at one point warns her not to do this too much, as it becomes complicated.
Also, there's implication that Amicitia had to complete this because she and Paradox were two alternate futures Twilight could have become, and by closing the loop, she locked Paradox's defeat in stone.
Suggested in the Empath: The Luckiest Smurf story "Days Of Future Smurfed" that Empath is supposed to create the memory artifact that will fall into the hands of Peyo, leading to his creation ofThe Smurfs, while Empath marries Smurfette, has a child through her as well as a grandchild and great-grandchild, the last of whom will become Traveler Smurf, who will travel back into the past to give Empath visions of the future that will lead to the creation of the memory artifact.
Deconstructed in the Ranma/Sailor Moon crossover No Chance For Fate in the first chapter until a random factor breaks the loop, setting up the rest of the story with Sailor Pluto hell bent on preventing the situation that caused it in the first place.
Jewel Of Darkness has a small one in the Rivalry Arc. Midnight goes to steal the Clock of Eternity, only to find it already gone. After the ensuing confrontation with Warp and trip to the canon universe, she ends up back in the museum five minutes before her first arrival, allowing her to steal the Clock before she even shows up.
Triangle has a very convoluted one. Jess comes to the harbor looking dazed and eventually ended up being on a mysterious boat and threw a masked killer overboard. She realizes she's in a Groundhog Day Loop by seeing herself boarding the mysterious boat and tries to break the chain by killing herself becoming the masked killer and getting thrown overboard. She drifted back to the shore where she was able to hitchhike back home seeing herself with her son. She killed her other self and wanted to dispose of the body which resulted in a car accident killing her son. She gets on a taxi to go to the harbor and the trauma seems to have caused amnesia. She comes to the harbor looking dazed and eventually ended up being on the mysterious boat, etc. etc. etc.
Bill & Ted: Bill and Ted demonstrate remarkable Genre Savvy by using Stable Time Loops to their advantage. For example, in the first film Ted's father has lost his keys; when Bill hits upon the idea of setting things up using time travel, he suggests they could go back, take the keys, and hide them somewhere; they immediately check the location and the keys are there. They're also careful to remind themselves that they need to set things up when they're done with the history report, otherwise it won't happen.
Also, they hear their future selves call Rufus "Rufus", which is why they use that name for him later when they become the future selves. He never actually tells them his name.
The climax of the second film revolves around this, as both Bill and Ted and Big Bad Denomolos try to use the same plan against each other; the boys disarm Denomolos with a sandbag and trap him in a cage, but he produces a key and a new gun. When the gun turns out to be a BANG Flag Gun (that says "Wyld Stallyns Rule!"), the boys point out that only the winners can play that game, and they set up the key and gun to fool him.
In The Final Countdown, the USS Nimitzgoes back in time from the early 1980s to just before Pearl Harbor. During their trip, one of their crew is left on an island and ends up staying there. Forty years later, he's running a defense company that helped design the carrier in the first place...and was the man who had sent Martin Sheen's character, an employee of his company, to be onboard the Nimitz at that time. This not only meant that person was present for the events but sending him to the Nimitz delayed her departure, which could have been what put her in the right place at the right time to be sent back in time.
Donnie Darko: The entire movie takes place in an unstable time loop, and the whole plot centers on trying to close it. When Donnie transports himself and the jet engine that killed him back in time, it closes the loop and negates everything that happens in the movie. However, this is never explicitly stated, resulting in a certain amount of Mind Screw.
In Grizzy Mountain, two kids go back in time to 1871. They're the ones who are responsible for keeping Grizzly Mountain from being blown up, and allowing the Natives to keep their land.
In The Terminator, the world-ruling SkyNet computer attempts to defeat the human resistance by sending a Terminator android back in time to kill the mother of resistance leader John Connor before he was born; not only does the Terminator fail, it turns out that if SkyNet had not made the attempt, Sarah Connor would not have met John's father and John would not have existed. There are theories he may very well not be the first John Conner and that John Conner was always supposed to exist son of Kyle Reese or not.
Terminator 2: Judgment Day (and a deleted scene from the first film) reveals that the technology used to create SkyNet was developed by researchers studying the remains of the Terminator android. Thus, the SkyNet technology was never invented by anyone, but came into existence within the time loop. The Third film points out that the events of the second only delayed Judgment day that Skynet was inevitable leading to the possibility that the events of the first movie accelerated them in the first place.
In theoretical physics, the above is known as a 'Picasso Paradox': if Picasso somehow went back in time and gave his younger self reproductions of his paintings, are Picasso's paintings then the result of the reproductions, or are the reproductions the result of the original paintings?
Then in Rise of the Machines, the Terminatrix reprograms SkyNet tech to awaken it, thus resulting in the Machine Rebellion, which ultimately leads to that same SkyNet sending back the Terminatrix to awaken itself...
Also, in the first film Kyle tells Sarah a message John gave him to memorize. In the second film we see that Sarah has given the message to John, so he can give it to Reese. So who wrote the thing?
A very, very detailed analysis of the time loops in the Terminator series is available here. That site makes the interesting argument that what we see probably is not the first version of the loop; information such as Kyle's message was initially generated in an earlier cycle, and mutated with iteration until the versions converged, and we're seeing the final 'stable' cycle.
The first one starts when the protagonist witnesses a murder as a child and the image of a young lady screaming in horror is burned into his memory. This memory is what allows him to travel back in time from the post-apocalyptic future, and what causes him to try to escape his superiors and start a new life in the past. He is shot by his masters while in the past, with his younger self watching, completing the loop.
The second loop occurs when the man travels from the ruins of post-WWIII Paris into a future where civilization has returned to its peak, gathers supplies, and goes back to his own time so the supplies can be used to rebuild society and allow that utopian future to occur.
The premise of Twelve Monkeys (inspired by La Jetee) is that Time Travel cannot alter history in any way — whatever you go back and do in the past, you've always gone back and done in the past. Cole remembers that as a kid, he saw his own death, which later happens just as he recalled it. The researcher (and the other time travelers) went back from 2035 to 1996 for one reason only — to gather information about the original virus (which had greatly mutated by their own time) of The Plague that had decimated humanity in 1996, so that a cure could be developed in 2035. The near-destruction of humanity in 1996 will always happen; the 'happy ending' is that humanity gains the chance to recover four decades later.
McCoy: You know, if we give him the formula, we'll be altering the future. Scotty: Why? how do you know he didn't invent the thing!
In the Novelization of IV, Scotty says that he did invent transparent aluminum, and that it was necessary to show him how.
The same thing also happens when Kirk sells the glasses he got from McCoy for some needed money. He even lampshades it.
Spock: Admiral, weren't those a gift from Dr. McCoy? Kirk: And they will be again. That's the beauty of it.
This isn't a proven time loop: logically, the glasses Kirk received as a gift in the future are simply the original pair, while Kirk selling the glasses in the past creates an older 'copy' of the glasses, the fate of which is unknown.
In any event, due to repeated loops, the glasses would eventually be millions of years old and fall apart. Either Kirk didn't think it through or he's simply being facetious.
In Somewhere In Time, there is a watch that an old lady gives to Richard Collier. Later on, Richard Collier goes into the past and gives the pocket watch to the much younger lady, who keeps it until the present. Also, Richard Collier's signature from the past in the book in the present — indicating that his trip into the past will be successful.
In Timerider The Adventure Of Lyle Swann, the protagonist from the present unwittingly goes back to the wild west and meets an attractive young woman. After getting to know her (at her insistence), she asks about a necklace, which he claims his grandmother gave him. Through the course of the film, he gradually realizes that no, these aren't a bunch of really intense historical re-enactors, while she comes to understand that he really is from the future. Just before he returns to the present, she snatches the necklace and holds it up, wordlessly and clearly explaining why she did it and who she will become.
In Split Infinity, A.J. goes back in time (via Mental Time Travel) to 1929. It turns out that she was responsible for saving the house and the barn from the stock market crash.
The original Planet of the Apes 5-film series. You can start at any of the films, and follow them around in numerical order to form the time loop (each film follows the previous one, the first film follows the fifth).
This can be placed under either Literature or Film, but both Michael Chrichton's Timeline and The Film of the Book include this trope. In the beginning of the story, the archeologists discover a sarcophagus of a one-eared man buried with his wife, seeming, for all intents and purposes, to be a knight. When the characters go back in time, one of them ends up falling in love, getting an ear cut off, and winds up staying in the past, thereby becoming the man in the sarcophagus.
The same could be said of the glasses found during the excavation. The glasses weren't left behind in the past, they were left in an alternate universe (and if they had the "foresight" to leave the glasses in place in the alternate universe so they could find them in the future of the normal universe just because they knew to leave them in place in the alternate universe past...).
Note that the novel states that they're not really in the past but in an alternate reality that's time-shifted from ours. Anything they do there won't affect their own reality.
Timecrimes involves a triple loop of sorts.. A man named Hector sees a girl stripping in the woods and is then chased into a laboratory by a man with a bandaged face and scissors. Hector is told by the lone scientist in the lab to hide in a machine, which sends Hector back in time an hour, causing him to become "Hector 2" while "Hector 1" is still watching the girl strip and being chased. At first the scientist and Hector think it's best for Hector 2 to lay low until Hector 1 is through the machine, but Hector 2 begins to realize that his actions are causing results that he saw as Hector 1. After he cuts his face and bandages it, then finds the girl and the scissors, he makes her strip and chases Hector 1 into the machine. Unfortunately during this Hector 2 witnessed his wife's death, so he returns in time again, becoming Hector 3, working to save his wife while Hector 1 watches the girl strip and runs, and Hector 2 makes the girl strip and chases Hector 1. Hector 1 and Hector 2 eventually vanish because they become Hector 3, closing the loop.
The Time Shifters avoids this trope for the most part, as time is shown to be subject to change. At the end, however, a dying man from the future recognizes one of the Feds, who likes to invent gadgets, as the future inventor of a temporal displacement device, which will open the door for time tourism. The Fed then notices an interesting device near the now-dead man and decides to hold on to it, not knowing it is a time machine.
Back to the Future has one moment that looks like an example: the scene where Marty is in the past and he plays Johnny B. Goode, by Chuck Berry. Chuck's cousin hears it and calls him to hear it on the phone, implying that's where he got the idea for the song. However, given that Marty has clearly not already changed the past when the movie starts, and Chuck could not have heard enough of the song and Marvin had no opportunity to write down or memorise the lyrics, it should be obvious that this was an example of Alternate Timeline.
Brazilian film O Homem do Futuro (The Man from the Future) ends up in one of those. Protagonist Zero ends up going back 20 years to the day of his prom, where he prevents his date from humiliating him, which ruins his life. This changes the future... but not for the best, specially as said date hates his guts. So Zero goes back to the prom again, stops his other time travelling self and instructs his date to humiliate him and not contact him for 20 years (which she does once Zero returns). During the prom, Zero also ends up creating the fortune that financed the time travelling process, by instructing a classmate that became a contractor to buy stock from Google and sell it before the 2008 crash.
Defied in Looper. The movie features the main character's future self going to the past to kill a boy who would grow up to become a crime boss. The movie ends with his present self realizing that his future self killing the boy's mother and ruining his life is what caused him to become a crime boss in the first place, so he ends it all by killing himself, making his future self disappear, presumably making a better outcome for the boy.
Except it doesn't happen during the previous iteration of the loop. Someone else kills the boy's mother and shoots him in the jaw, as Old Joe killed his future self.
Evil Dead 2 has a simple one that is briefly touched upon. The Necronomicon contains a prophecy with an illustration of a man with a chainsaw appearing in the Middle Ages, and at the end of the movie Ash ends up being sucked through time to the Middle Ages and serving as the basis of that picture.
Shock Labyrinth... maybe. The kids are scared in the past by themselves in the future. The future Motoki grabbed his younger self briefly and the future Ken pulled Yuki's body away as Miyu watched. Then again, Yuki might just be messing with them.
In Free Birds, Jake reveals that, when he was little, the Great Turkey appeared to him in the sky and told him to find Reggie and use the secret government time machine to travel back to the first Thanksgiving and prevent it. Near the end, Reggie finds out that he's supposed to go back to Jake's younger days and pretend to be the Great Turkey with S.T.E.V.E. the Time Machine throwing his voice.
Subverted in Altitude. In the opening a mysterious plane that appears out of nowhere crashes into Sara and Bruce's plane when they are kids and kills both their parents. In the present day it's revealed that the plane was in fact the one Sara and Bruce are currently piloting. In the conclusion of the film they enter a temporal vortex but manage to avert another crash while killing themselves, allowing their child selves to live with their parents still alive.
In Godzilla vs. King Ghidorah, time-travelers try to remove Godzilla from history by going to an island it was living on as a dinosaur before mutation during WW2. They teleport the dinosaur they find into the Bering Sea, away from getting hit by nuclear tests. However, nuclear waste and Russian submarines disappearing during the 1970s end up turning the dinosaur into the Godzilla seen in the first Heisei series entry The Return Of Godzilla. However, this information is discovered too late as a Japanese nuclear submarine seeking out the dinosaur to try and mutate is destroyed by Godzilla and only making him bigger.
In Alterien, Oberon learns he's responsible for the creation of one of his greatest benefactors, Sol 3 United, from nearly 400 years before he was born.
In Black Maria the protagonist and her mother go back in time while turned into cats to watch events unfold, only to become responsible for the events in the first place.
In The Merlin Conspiracy, there is a doozy: Nick's part of the story begins with him sidestepping into other universes willy-nilly. A man named Romanov shows up to kill him. After he spares Nick's life, Nick later follows him to his personal island/mini-verse, where he is deathly ill. While taking care of Romanov, a Knight Templar and his two wards (Joel and Japeth) show up to finish Romanov off while he's down. They are dispatched, and one of the boys treads on an egg. Nick laughs. Several universe hops later and Nick winds up in Blest, where there is a ten year difference between Romanov's world, and the two boys are now the Big BadChessmasters who kicked off the whole plot to begin with, and are the ones who not only sent Romanov to kill Nick, but also gave Nick a special virus to kill Romanov, which was what made him sick earlier. Which Nick himself accidentally gave them the idea to do. He accused them on Romanov's island -while they were still young- of paying Romanov to kill him. Plus several other, minor time-related things, such as answering the phone while Romanov was ill, causing wife to leave him. She winds up being Joel and Japeth's sidekick.
There was a short sci-fi story where a king, who is always coming up with crazy and unhelpful schemes to improve his small country discovers that a time traveler is helping his advisers to offset the impact of his schemes. He captures the time traveler and forces him to take them both into the future so he can see how things will turn out. They arrive in ten years in the future and that the country is prosperous beyond his wildest dreams, so he asks a passerby "What was the big change that brought about this golden age?". The passerby answers "It all turned around when the crazy king disappeared ten years ago and the advisers started ruling the nation". As the king wonders why he disappeared a decade ago, the time traveler shuts the door to his time machine, leaving the king in the future.
In Douglas Adams' Life, the Universe and Everything, the poet Lallafa was known for writing beautiful poetry on habra leaves in the middle of a rainforest... So some time travelers picked him up from the rainforest and put him on the talk show circuit in the future. Of course, he had to write the poems at some point, so they just sent him back to the forest with a book of his poetry and a bunch of habra leaves...
Far from the only one in the series. Arthur, of course, met with Agrajag before one of the many deaths of his previous forms had ever occurred, and so he knows that he's going to be able to escape when Agrajag tries to kill him anyway. Also, the entire arc with the Golgafrinchams.
As explained by Ford Prefect, every form of Time Travel in that universe is a Stable Time Loop.
Zaphod Beeblebrox is his own ancestor and descendant.
That series of books is definitely Timey-Wimey Ball. People are trying to build an ion factory. They don't finish it in time so they keep pushing the construction start date back farther into the past, until the cathedral that was originally in the spot was never built in the first place. It then states that photographs of the cathedral suddenly became immensely valuable. Huh? Time travel, like everything else in those books, runs on Rule of Funny.
What's more, in the first book, it's suggested that the origin of life was caused by the Infinite Improbability Drive — which was, of course, later built by living creatures.
In the story The Red Queen's Race by Isaac Asimov, an attempt to change history by sending modern scientific knowledge back to the ancient Greeks is subverted when the person translating the information finds out about the plan. The translator creates one by censoring the translation to include only odd bits of surprisingly advanced knowledge that actually turned up in the ancient world (according to him, it wouldn't have mattered that much in any case - ancient Greek mentality has little use for applied sciences). Also, it's decided that doing this was necessary for history to happen as it already did.
Also implied in "The Last Question" ("Can entropy be reversed?") when the Cosmic AC has finally compiled enough data to come up with an answer (despite the end of the Universe) and says LET THERE BE LIGHT!
Not to mention they go back and close down each time loop so that they never actually happened, leaving the protagonist deeply confused as to how he/she still exists. The person she's with tells her basically to shut up and deal with it.
The entire plot of Artemis Fowl: The Time Paradox. A picture of Artemis chasing himself through the timestream is on the cover. In going back to the past to rescue the lemur, Artemis managed to draw the attention of the younger Opal Koboi. She then followed them to the future, but arrived a few days early, in order to set off the events that would cause them to time-travel in the first place.
Plus, Artemis' adventures in the past are implied to inspire his younger self to research the faeries and begin exploiting them in his schemes.
Lester Del Rey's 1951 short story "...And It Comes Out Here" features a time machine that's created by a time loop.
In the Thursday Next Novel The Eyre Affair, Thursday meets herself, and receives the news that the Big Bad is alive, and is told to travel to Swindon. As a result of the travel, she ends up caught in a patch of Bad Time, and arrives to deliver the message.
Later in the series, it's revealed that the various methods of Time Travel work on the assumption that someone will invent Time Travel, and deliver that technology to their current time. This starts causing trouble when people find that Time Travelwon't be invented.
Also, Thursday's father gives her his chronometer. He got it years ago from her, after she got it from him.
A debate runs throughout the book about who really wrote William Shakespeare's plays. At the end of the book, Thursday's dad, a time traveler, reveals that no-one ever wrote the plays; when he went back in time to the corresponding period, the plays weren't around. So, he gave them to William Shakespeare to produce. Thursday's dad tells her not to worry about where the plays actually came from, as these things happen often.
In Something Rotten, Thursday meets her father when he turns up to thwart and investigate an assassination attempt on her. He's there because of a conversation they had "three hours ago", and refuses to answer Thursday's questions because he's already explained all that and can't be bothered to go over it again. It turns out that through a minor confusion (the aforementioned chronometer is broken, so Thursday gives him "hers"), the previous meeting is in fact three hours in the future from Thursday's point of view. Three hours later, Thursday happens to be passing her father's office and decides to go in to find out what he'd been talking about earlier. At the end of the conversation (which is equally as confusing for her father as the earlier chat had been for Thursday) she mentions that she was only there because of their talk during the assassination attempt, and her father agrees that perhaps he should go and investigate...
The Robert L. Forward novel Timemaster demonstrates the use of a Stable Time Loop generated by a wormhole (technically, a "closed timelike curve") as an offensive weapon.
The protagonist of The Stainless Steel Rat gets dumped into Stable Time Loops so often that he treats it as a normal occurrence. Usually they're fairly brief, but The Stainless Steel Rat Saves The World is a novel-length stable time loop. Or more accurately, it's one stable time loop after another for the whole book, with one unstable time loop for variety.
The Technicolor Time Machine hinges on several Stable Time Loops. The premise is that a movie studio is about to go bankrupt, and so in desperation they try funding a seemingly crackpot physicist who's working on a time machine in exchange for the use of the completed model. It works, of course, so they take a camera crew back in time to film a historical about how the Vikings discovered America — they don't have to pay for sets or actors this way, and they can get the whole film done in a couple of days so they'll be able to show the bank that they have an asset they can monetize when the next loan payment becomes due. When they find the Viking that history says is the discoverer, however, he seems completely uninterested in attempting the journey... until they nudge him with a little bribery and technical assistance. A few other Self-Fulfilling Prophecies occur later on, including a note that nobody wrote and a vicious practical joke one of the characters plays on himself in revenge for that same vicious practical joke he played on himself 'earlier.'
Actually, they don't know that this Viking is the discoverer. He's simply the first one they encountered, so they decide to go with him, especially since he's willing to work for crates of Jack Daniels. Another time loop happens when a ship arrives for him, which the seller claims that he bought. This clues the time travelers that they need to go back and buy the ship. They have the Viking sail for Vinland (the New World) and then time travel to Vinland to film the ship arriving. After the filming is done, they start wondering if they'd just changed the past by having someone else other than Thorfinn Karlsefni lead the expedition. The Viking reveals that this is his real name. The time travelers realize what they have done by accident. Also, the director is told later that the person who supplied Thorfinn with the ship was Bjarni Herjólfsson, which sounds like a bastardized name of the director.
"The Secret of Stonehenge" is a short story which features a group of scientists setting a camera on a time machine in the middle of Stonehenge and sending it back to the estimated time of creation and then sending it on a series of short jaunts forward in time to capture what had been going on. After the machine disappears, they notice that sending it that far back in time left a ghostly image for a moment. Moments later, they realize the reason Stonehenge was built... in tribute to the ghostly thing that kept appearing in that location over the years...
The Robert A. Heinlein short story —All You Zombies— uses the same device. The protagonist tells a bartender a story in which he introduces his mother, actually himself before a sex change, to his father, actually himself after the sex change. He is also the bartender, sent back in time to recruit himself into the time-travel police.
In The Door into Summer, the protagonist travels into the future and sees machines he's almost sure he invented. So on that hunch, he finds a time-machine that can send him back. He makes some arrangements, returns to the future by cold sleep and lives happily ever after knowing the people who tried to ruin his life got their just deserts.
James Hogan uses a Stable Time Loop approximately 50,000 years long in the third book in the Giants series.
Time Travel in the Dragonriders of Pern books by Anne McCaffrey operates on this principle. Much of the Time Travel is undertaken knowing in advance that it will work ("since I've already done it, I might as well go do it..."). What isn't, is of the form "I think I'm the one who did it, so I'd better go do it..."
Behold the Man by Michael Moorcock: Karl Glogauer tracks down the real Jesus, son of Mary, and finds that he's an idiot; so he...
The Time Traveler's Wife by Audrey Niffenegger is full of Stable Time Loops. For example, on one of Henry's visits to his wife-to-be Clare in the past, he dictates to her a list of dates in her childhood when they're going to meet. They meet on those dates only because she knows he's going to appear — there are some other times when he appears, but since those dates aren't on the list, she doesn't know he's there. When they meet as adults in real time, she gives the list back to him so he can memorise it. Where did it come from in the first place? Seemingly nowhere. Henry also taught his younger self a number of skills he knew he would need, such as how to pick locks. His theory is that to prevent Temporal Paradox, he has free will while he's living in normal time but not while he's time traveling.
One time loop is Henry and Clare's marriage. From Clare's perspective, she meets Henry when he travels back in time to her childhood, lands in her backyard, and introduces himself as her future husband. From Henry's perspective, he meets Clare when he runs into her in a college library and she tells him that she's known future-him for most of her life and that they're going to get married. So when did they meet for the first time? The answer is "Both": He first met her at the college library, and she first met him in the Meadow. Because of Time Travel, they both met a version of the other who was ignorant of their future relationship/marriage.
In H. Beam Piper's short story Flight from Tomorrow, a tyrant in the very far future forces a scientist to create a time machine for him as the ultimate escape route, and he uses it to flee into the past from a rebellion at the beginning of the story. He is not expecting a Stable Time Loop — quite the contrary — but the scientist not only left out some important information but sabotaged the machine, so that he went back not to the time he had researched, but to the mid-twentieth century. The tyrant is hunted down and killed as a plague-carrier. The scientist in his own time explains to the rebels that they cannot pursue the tyrant into the past, or they will meet the same fate; the scientist's audience realizes that a mysterious artifact from the distant past must be where the tyrant's body was covered over with concrete to prevent further contamination.
In The Anubis Gates by Tim Powers, the protagonist, Brendan Doyle, becomes the victim of Grand Theft Me in the 1800s and realizes that he is destined to be the poet, William Ashbless, whom he was researching in the present day. Partway through the book, he panics on realizing nobody ever wrote Ashbless's poetry — he copied it from memory earlier — but then shrugs it off, deciding that as long as it was there, nobody would be bothered.
The Discworld novel The Last Continent is essentially a single, but quite complex, one, in which the problem Rincewind has to solve is caused by the wizards accidentally going back in time while looking for him. It also includes Ridcully dismissing Ponder Stibbons' worries about the Butterfly of Doom (or Ant Of Doom in Ponder's example) by concluding that history depends on you treading on the ants you've already trodden on.
Specifically, Ridcully's argument relies on the old "you can't step on an ant if you don't exist." His logic is that if they're in the past NOW, then they've already been there thousands of years ago, when it was now. Therefore, anything they do, they've already done (because it's the past and the past has already happened), and it's vitally important that they do whatever they do, because if they didn't, they wouldn't have done it and they'd have done the different thing instead.
Night Watch subverts a Stable Time Loop: there was a real Sergeant Keel the first time around, but Vimes' and Carcer's arrival from the future gets him killed ahead of schedule. Vimes must assume Keel's role to force stability on the Loop, and while the general outcome is the same, several of the specific events are different.
On a smaller scale, minor recurring character Mrs. Cake is a psychic who is known to answer peoples' questions before they ask them; she then insists they ask, to stabilize the time loop, or she'll get a migraine.
In Interesting Times, Hex answers a problem before it is asked. The wizard in charge eventually enters the problem to appease causality, but not before hiding in the privy for an hour and a half.
In Eric, Rincewind travels back in time to before life existed on the Discworld, and drops a partially eaten sandwich in a tidepool. The microorganisms in the tidepool become the ancestors of all life on the Discworld, including Rincewind (but not including the sandwich ingredients, because the sandwich didn't originate from Discworld; it was given to Rincewind by the creator of the universe).
Played with extensively in Pyramids, particularly in the construction-crew's "doppelgangs" and Dios's fate. The paradoxes entailed are lampshaded when the engineers discuss the option of paying their loop-duplicated workers with loop-duplicated money.
In Soul Music, Susan travels to the past and sees her father fight Death at the conclusion of Mort. Death spots her watching and recognizes her as the child of Mort and Ysabell, which convinces The Grim Reaper to stabilize the loop and spare his apprentice so the girl he's just spotted can be born.
Also the first paragraph of the book takes place later in the story, despite being chronologically first.
In I Shall Wear Midnight, elderly Tiffany insists this trope is not in effect, as each iteration of this time-traveller's encounter with young Tiffany will actually result in a different conversation. The fact of their encounter is stable, but the details aren't set in stone.
Harry Potter and the Prisoner of Azkaban. Harry is saved from dementors by a Patronus Charm cast by a mysterious figure who he thinks is his father. After he travels back, he eventually finds himself in the same place and waits for his father to show up... and then realizes HE was the mysterious figure, and saves himself. In fact, he only gains the ability to cast a true Patronus for the first time because he realized that he had already done it. Also, as Harry, Ron, and Hermione first head out to adventure, they hear noises that turn out to be Harry and Hermione as they complete adventure!part I.
This is often used as a justification for being unable to change history in the Potterverse, but it seems to contradict what Hermione tells Harry in Prisoner of Azkaban about wizards and witches having to be careful to avoid killing their past and future selves. One can explain this in various ways, but the end result is that canon is not entirely clear.
Possibly subverted in the Star Trek: Deep Space NineExpanded Universe trilogy Millennium, which involves a convoluted Quasi-Stable Time Loop in which the actions of a future Picard, Vash, and Nog help cause the creation of their alternate future, followed by the retroactive destruction of that same future. During the story both Dax and Miles O'Brien continually insist on maintaining one, but by the end it seems their actions can only succeed because of three people who shouldn't exist.
In the Warhammer 40,000 novel Desert Raiders, a Tallarn regiment is dispatched to an uninhabited planet to investigate a mysterious psychic distress call. After landing on the planet, the regiment encounters a Tyranid splinter group and is forced into a desperate last stand. One of the psykers traveling with the regiment dispatches a warning signal in their final moments — the same signal the regiment had been sent to investigate in the first place. The implication is that, in traveling through the Warp, they had gone back in time before reaching their destination; indeed, the Warp in the 40K 'verse is known to do some strange things to the flow of time...
In Animorphs, In the Time of Dinosaurs, the Animorphs go back in time to the Cretaceous, fight the antlike alien Nesk for a nuke to explode (so that they can undo the time travel) and the Nesk divert a comet to the only home of the Mercora (the friendly aliens). The Mercora wanted the nuke so that they can explode and stop the comet from hitting, but Tobias and Ax rig the nuke not to explode, as the comet was the one that ended the dinosaurs (opening the way for humans to evolve). The force of the comet ends up sending the Animorphs back home.
In #13, The Change, the Ellimist sends Tobias back to the night before the infamous construction site incident that started the whole series. Tobias thus convinces his past self to team up the next evening with Jake and Marco and then to take that shortcut across the shady construction site.
Also, the whole Elfangor's Secret book.
Dragonlance Legends reveals that humans, elves, and ogres can time-travel only to observe. This is how it's supposed to work. Throw in the unnatural races, which were not created at the beginning of time, like dwarves, gnomes, and kender, and you have problems. So, Raistlin during the Twins Trilogy would be caught in a stable time loop which essentially just causes him to kill himself over and over again every 400-odd years... if it weren't for Tasselhoff's (a kender) jumping into the spell at the last minute and mixing everything up.
Played with in Kurt Vonnegut's Slaughterhouse-Five where the character lives in a personal unending non-chronological time loop where he lives out every moment of his life repeatedly, with all of his own memories, after becoming Unstuck in Time. In the novel he is suggested to have lived out all these moments more than once and always does the same things every time making it a stable time loop of sorts...
One book continuity of Red Dwarf or the other puts Lister as the creator of the universe, having gone back to that point in time to see what happened.
The William Tenn short story "The Discovery of Morniel Mathaway" is built around a stable time loop that involves an art historian meeting the object of his research.
The short story entitled The Sky Looked Strange Today involves a man driving on the freeway when he is distracted by a peculiar aurora on the horizon. When he looks back at the road, he crashes into a taxi cab that has started a pile-up, but time slows down for everything but the man. He gets out of his car into a motionless world when suddenly, his "guardian angel" appears and tells him that his next door neighbor caused the crash. He takes the man back in time, one hour earlier, and leaves him to figure out how to stop the pile up. In an impulse effort, the man slashes his neighbor's tires and, feeling he has succeeded, takes a cab to work before his past self sees him. As he rides in the cab, he notices the aurora again. Unfortunately, so does the driver. The man forgot that his neighbor works for the cab service. So, the neighbor rear-ends a car, causes the pile up, and just before the man is killed by his past self (still distracted), he says his odd last words: "The sky looked strange today..."
To Say Nothing of the Dog is built entirely around this trope. The main characters spend virtually the entire length of the novel time traveling back and forth to the Victorian era, trying to correct the actions of one of them that threatens to change the entire course of history.
Used quite effectively in Simon R. Green's Deathstalker series. Simon Deathstalker and his companions receive superpowers by passing through the Madness Maze, an alien artifact built to combat a terrible menace that the aliens knew about. After the protagonist dies his true love, Hazel D'Ark, is driven insane by grief and resolves to go back in time and become so powerful that she can prevent it from happening. It turns out that she is the horrible unknowable menace the Madness Maze was originally designed to fight.
In Andrey Livadny's Ark, all the worlds encountered by the main character turn out to be biospheres built into the titular Ark for the various alien species on-board, an enormous Generation Ship literally built out of the Moon by humans thousands of years before in order to basically follow the Star Trek mantra. Most of the logs are lost, and the ship's AI has no idea where they are or even what year it is. Without the crew to aid in maintenance, the Ark is in a dire state of disrepair. They manage to find a yellow dwarf star nearby with a habitable planet. Since the spherical craft was never meant to land (imagine the tidal forces from a Moon-sized object), they are forced to drop it in water in hopes of cushioning the impact. They do as much as they can to brake before hitting the atmosphere. The main character, who is now an electronic consciousness in the ship's computer, separates the command module from the rest of the ship and lets it fly away from the planet with himself and the ship's AI still in it. The Ark somehow manages not to break apart on impact, although it creates massive tsunamis and empties out the sea they hit. Most of those on-board survive (probably due to some sort of Inertial Dampening). One of the first people to get out is an old shepherd who introduces himself as Noah. The novel ends with the protagonist returning to the planet after several thousand years and teaching the inhabitants several important values, including "Thou shalt not kill."
Time travel in Poul Anderson's novel There Will Be Time seems to require these.
In "Explain the Internet to a 19th Century Street Urchin", from the book ''Everything Explained Through Flowcharts", these are some of the more favorable outcomes. The non-temporal outcomes usually result in your death.
The short story collection Short Trips: Time Signature follows a single piece of Vortex-threatening music through the Doctor's life. Since the book is in extreme Anachronic Order, following neither the music nor the Doctor linearly, it takes a bit of working out, but essentially the music was sent to the planet where the Doctor first heard it by someone who'd heard it from the Doctor. ( But then the same person helps the Doctor disrupt a key point in the chain, so none of it happens after all. Wibbly-wobbly timey-wimey.)
The events of the novel The Stone Rose begin because Mickey sees a statue of Rose in the British Museum. By the end of the story the statue still hasn't been made, so the Doctor carves it himself. In the same book, a vial of mysterious liquid turns out to have been created by the Doctor, by running the dregs of the vial through the TARDIS's Matter Replicator, and taking the result back in time.
The Fourth Doctor short story "Breadcrumbs" has the Doctor going to a lot of trouble to collect various three-dimensional data fragments and run them through a reversed Matter Disperser in order to find out what they are. The last fragment is very close to a wormhole, and he just has time to register that the "message" is another Fourth Doctor, before he gets sucked into the Vortex, and ends up on a deserted island on an unknown planet. His only hope is to rewire the Matter Disperser correctly, and transmit himself as a series of three-dimensional data fragments...
There and Back Again by Pat Murphy has a mysterious note in the protagonist's handwriting that appears at the beginning of the book, and a mysterious message asking for help that gets a number of secondary characters to arrive at the climax of the book in time. Both turn out to have been sent by the protagonist himself at the very end of the book, after he goes back in time.
A common theme in the Xeelee Sequence books by Stephen Baxter. The Xeelee, who first evolved who-knows-when-and-where, reach back in time to refound their civilization at the very beginning of the universe. This gives them a multi-billion-year technological jump, which they'll need to fight a war which would have destroyed them long before they could reach back in time. It's actually to escape the universe— the war was already lost and was always unwinnable.
In The Dandelion Girl, a man whose wife is away encounters a girl in her 20s coming out of the woods who looks somewhat familiar and wearing a strange-looking dress. She talks to him a little and then goes back to the woods. She proceeds to return several times and, eventually, tells him that she is from the future. Time travel is a possibility where she's from, but the government has banned it for fear of changing the past. Her father secretly built his own time machine before his death, as he believed that time is immutable and everything has already happened. In the meantime, the man's wife starts to act a little strange towards him, as if she suspects he is spending time with another woman. The girl is missing for several days, and then comes back saying that this is her last visit, as the time machine is about to break down due to lack of maintenance. There may be enough left in it for one more trip. As she disappears into the woods, he follows her but sees only a bright flash of light. He returns to the house and looks in the attic for something, only to find his wife's old things, which also include the same strange dress the girl wore, the same dress his wife wore on the day they met years ago. Everything suddenly clicks in his head, and he realizes he had been married to her all along.
Warrior Cats also features one. In Starlight, the cats find a perfect (and uninhabited by other cats) spot to live. If there had been other cats, they wouldn't have been able to stay there. Later, in Long Shadows, Jayfeather travels into the past and convinces the cats living there to leave for the mountains, which he could not have done had he not lived there. Then, Rock appears and tells Jayfeather that he remembers that Jay's Wing (the cat everyone mistook Jayfeather for) disappeared after the cats left for the mountains. Because of this, he takes Jayfeather back to his own time, causing his memories of Jay's Wing's disappearance. Also, in Outcast, Jayfeather met the Tribe Of Rushing Water, and learned their customs. Then, in Sign Of The Moon, he travels back to the Ancient Cats and teaches them the Tribe's customs, allowing them to become the Tribe.
The entire plot of When You Reach Me is Miranda slowly discovering that she is in the middle of one of these.
Sergey Lukyanenko and Yuliy Burkin's novel Today, Mom! has two brothers being taught Ancient Egyptian by their archaeologist mom. They end up discovering a time machine inside an ancient artifact and traveling to the future and then the past. After saving a young girl from being married to a dying pharaoh (she would be buried alive with him), they take her to the 20th century and leave her there to start a new life. When they get back to their own time (1993), they are attacked by the mummy of said pharaoh who has come back to life. Suddenly, their mom bursts into the room and destroys the mummy with a weapon from the future. The boys realize that the girl they saved is their mom who knew what she was doing by teaching them Ancient Egyptian.
A millennia-long time loop is central to the plot of Aleksandr Zarevin's Lonely Gods of the Universe, although it's not revealed until the second half of the book. Of course, the characters realize that the time loop is far from stable and will inevitably collapse after 5 or 6 cycles (what that means is anybody's guess), destroying everyone and everything in it. They spend the rest of the novel trying to break out of the time loop, namely by preventing their births, while making sure that their present selves stay alive. Let's just say the temporal mechanics get very confusing by the end.
A smaller time loop occurs in the middle of the novel. The main character is asleep in his apartment, when he hears a loud thud in the next room. He finds a strange object that appears to have been neatly sliced diagonally. Not sure what to make of it, he throws it in the back of his closet and forgets about it. A year later, him and his friend are experimenting with a strange machine they built, which appears to be a mix of a teleporter/portal. One of the tests is a long object specifically made for this. In the middle of the test, power cuts out, resulting in a Portal Cut. However, the part of the object that went through is nowhere to be seen. The main character quickly runs out and brings back the other part from his closet, explaining what must have happened. Eventually, they get additional funding and turn it into a Time Machine.
Additionally, by preventing their own births, the Human Aliens are also saving their own civilization from a nuclear war, which resulted from one of them creating a teleporter (which they used to get to Earth).
Comes up in Dinoverse. Bones from a large dinosaur closely related to Tyrannosaurus rex were found at a site called the Standing Stones, a series of, well, standing stones. Bertram puts a shard of one of those bones in his science fair project, which accidentally turns out to be a time machine that sends his mind, and those of some people around him, into the past and into the bodies of dinosaurs and a large pterosaur. They get a message from the distant future, sixty years after the time machine came on, telling them that their bodies had been in comas for sixty years but someone had found a way to fix things. If they could just get to the site of the Standing Stones, they could go back. On the way there is discussion as to whether they'd already failed, and when they got to the place there were no stones, plus they got attacked by a large Tyrannosaur and barely managed to kill it. Turns out it was the same dinosaur, and they had to set up the stones themselves before they could go back.
Count and Countess makes use of this frequently. The two main characters, Vlad Dracula and Elizabeth Bathory, have been writing letters to each other across time since they were young children, and often what one character writes to the other will have a large impact on the recipient's timeline, depending on how he/she acts on it.
In Barrington J Bayley's novel "The Fall of Chronopolis", a gay man called Narcis travels back five years to seduce his younger self away from the latter's boyfriend. Five years later, they realise someone will soon arrive to destroy their relationship. The book doesn't explain how the traveller didn't remember this had already happened.
Toward the end of The Secrets of the Immortal Nicholas Flamel series, the conflict becomes less about preventing bad things from happening and more about traveling back in time to ensure things happened the way they did.
In the Elephant & Piggie book "We Are In A Book!", Gerald panics near the end because he doesn't want the reader to finish. Piggie solves the problem by asking the reader to read the book again... which begins with Gerald whispering to Piggie, "I think your plan worked."
In the adolescent novel The Eyewitness by Caroline MacDonald, an eleven year-old boy inadvertently travels forward in time and befriends a teenager whose grandfather committed violent suicide several years earlier. At some point in his life, the time traveler realises that he was that man, and when the time comes around, he kills himself because it is his fate to do so.
The short story The Janus Equation has a bizarre version: A man is seduced by and has sex with a mysterious woman who disappears after becoming pregnant. It turns out that the woman was himself travelling back in time after a sex change. First there's the obvious loop of him getting the sex change and travelling back to do that in the first place, but then Fridge Logic kicks in and you realize that since his/her/their child was made from one person's genetic material, will that child actually become him/her/them? Not necessarily — twins aren't clones — but you never know with time travel.
In Noob, the Galamadriabuyak tower transports players in random places in the past to have a Boss Fight. All these fights are stated to be be this trope, as the game world's history will not change as long as the boss is killed.
In Theirs Not To Reason Why The Immortal was born two centuries in the protagonist's future, then cast back in time 15,000 years by the Feyori. She rescued a group of humans from tectonic upheavals on Earth and transported them to a distant planet, which eventually became the V'Dan Empire, and founded a religion there predicting Ia's coming as the Prophet of a Thousand Years. This also allows Ia to steal designs for future technology from the Immortal's records.
Live Action TV
In Smallville, "Apocalypse", Clark goes back in time back to Krypton to protect his baby self from Brainiac.
One of Jim's Office pranks involves sending Dwight faxed warnings from "Future Dwight".
In one episode of The Red Green Show, one of Ranger Gord's educational shorts had him teaming up with his future self and going back in time to prevent a forest fire. After the two meet and team up with Past Gord, Future Gord explains his information shows the fire will be caused by lightning, which strike Red and Harold. The three Gords violently put out the fire and after looking like the usual Everybody Laughs Ending, the three Gords decide to go to the future and celebrate. However, sparks from the time machine taking off end up causing the fire in the first place.0
Babylon 5 has two of these, related to the same incident. The two-part episode "War Without End" in the third season has the protagonists cause the mysterious time incident on Babylon 4 that happened in the first season episode "Babylon Squared"... at the conclusion of which, an important character travels back even farther in time to become the cause of one of the show's central prophecies.
Not to mention becoming the ancestor of Delenn, one of the show's main characters, whose own decision at the start of the war, started the chain of events that led to Sinclair's Time Travel.
In this case, the Time Loop may be neither stable nor pardoxical: the Vorlons deliberately set out to create the Time Loop and what we see on screen may be neither the first nor the ultimate form of the loop.
There's also the part where Sinclair's survival is directly dependent on him eventually going back in time and becoming Valen, the ancient leader of the Minbari. Using an artifact Valen gave them, the Grey Council determines that Sinclair has Valen's soul, figuring that Valen reincarnated, when it was, in fact, the same soul. Thus, humanity, and Sinclair, were spared, allowing Sinclair to go back in time...
In the Third Doctor serial Day of the Daleks, humans from the future attempt to blow up UNIT headquarters to prevent someone from bombing a ministerial-level conference to be held there, starting World War III and allowing the Daleks to invade. As it turns out, it is their bomb that they are trying to prevent.
There's also City of Death, in which an alien whose mind was split several ways across time after his space-ship landed on Earth and exploded. His past selves hid various treasures to be found by his future selves (including multiple copies of The Mona Lisa!), which were to be sold off and used to get the materials to create a time machine so he could go back and prevent the explosion — something The Doctor might have helped with had he not discovered that the same explosion was the "lightning bolt" that stirred up the primordial soup to begin creating life on Earth...
The Fifth Doctor story Earthshock also is an example. A human ship is sent back in time and causes the extinction of the dinosaurs, the dominance of Homo sapiens and the creation of the ship. It also kills Adric.. So, really a win-win situation.
The Curse of Fenric reveals that Ace only exists as the result of a stable time loop: she befriends her grandmother as a young woman, and when disaster strikes sends her to a specific address in London with Ace's infant mother.
In the first season of the new series, The Doctor and Rose are followed everywhere by the words "Bad Wolf" — in the final episode, Rose saves The Doctor's life and uses the time-bending power of the TARDIS to deposit the words in the past, in order to inspire her to go forward into the future and save The Doctor's life, which ends in her putting the words into the past, etc., etc. This also crops up a few times in the second and third seasons (since the words were placed all over time and space, there's no reason for them to stop showing up just because they're not needed anymore), and more times than you can shake a TARDIS key at in the Ten/Rose Expanded Universe novel The Stone Rose. The phrase also turns at the cliffhanger of the fourth season episode Turn Left (with all written words, from the Doctor's point of view being replaced with "Bad Wolf" — even the TARDIS' signage), in which it heralds Rose crossing over back into the main universe.
The Shakespeare Code is a minor example — the Doctor quotes lines from Shakespeare's works to the man himself. Some of them he recognises, but some of them he hasn't got around to writing yet.
The episode Blink also repeatedly uses it. At one point, the Doctor pre-records his half of a conversation with another character; when the other character has the conversation, it's written down, and the Doctor works off it to record his half. Also, his half is recorded as an easter egg on 17 specific DVDs; when the Doctor tells a video executive which discs to put the recording on, he's working from a list someone in the future made of DVDs that have the video on them.
Sally: "You're reading from the transcript of a conversation you're still having?"
Also used "for cheap tricks" (his words) in Smith and Jones; when Martha first meets the Doctor, he stops in front of her on the street, takes off his tie, and walks off. When they meet at the hospital again, the Doctor can't ever recall meeting her. At the end of the episode, he goes back in time and takes his tie off in front of Martha in order to prove that the TARDIS is a time machine.
Used in the canonical special Time Crash, where the Fifth Doctor is brought forward in time and meets the Tenth. A problem develops which the Tenth Doctor instantly solves, working from his memory of when he was the Fifth Doctor in this very situation, watching his future self solve it. In fairness, this was playing for laughs, and (unlike the Pandorica example) the problem could have been easily solved some other way if the writer hadn't chosen to be cute.
Fifth Doctor: "You only knew what to do because you remembered being me watching you doing it."
Tenth Doctor: "Wibbly-wobbly"
Fifth & Tenth Doctor: "Timey-Wimey"
Is abused in The Big Bang, in which the Doctor is rescued from the Pandorica by Rory wielding the Doctor's own sonic screwdriver, given to him by the Doctor in the future after Rory rescues him. The Doctor then goes on to plant hints for Amelia to follow to resurrect her future self.
This episode also features possibly the most pointless stable time loop ever conceived. Young Amelia is thirsty, so the Doctor jumps back in time several hours and steals a drink. He then returns to the present and gives the drink to her. The reason she's thirsty in the first place is that a few hours ago someone stole her drink.
Given that Steven Moffat frequently writes in lines that poke fun at Dr Who tropes (Curse of Fatal Death is a long string of these!) this drink-loop is probably employed as an in-joke at how much the trope is being abused in this episode. In fairness though, they do acknowledge it on screen in this episode (and again in The Impossible Astronaut) that they're only able to do all this time-looping because the universe is collapsing.
In Time, the second part of the 2011 Red Nose Day comedy special, we get three of these in as many minutes, two of which play this trope straight (Amy doesn't understand what her future self said, but still says it herself, even though the Doctor doesn't even explain it to her, and the Doctor waits for his future self to tell him which lever to use despite having no idea despite the time loop being a few seconds long) and the third of which justifies it:
Present Rory: Do I have to remember all of that? Future Rory: It just sort of happens. Present Amy, flirtatiously: Hi. Future Amy, flirtatiously: Hi.
As of A Good Man Goes To War, the Doctor's name turns out to be one of these. The meaning of the word was apparently already established when he chose it, but due to centuries of crosstime adventuring, it turns out 'doctor' means healer because of him. However, in some places, it means 'mighty warrior' because of him.
River Song's whole existence is a series of these. She is named after herself (twice!), she is directly responsible for her parents hooking up, she's indirectly responsible for her being conceived in the TARDIS, etc. In Forest of the Dead the Doctor manages to save her imprinted memory, because he figured his future-self wouldn't leave her to die, and his future-self, knowing that he didn't, thus created a way to save her...
In Let's Kill Hitler, Amy and Rory make a crop circle as a dramatic gesture to leave a message in time to get the Doctor's attention. They were most likely inspired by River Song's various messages to the Doctor previously in the series. However, it turns out that their best friend Mels is River, and this is her first time meeting him as an adult. So this incident is probably where she got the idea for leaving unusual messages like this.
Heck, River's whole life is a giant time-loop! She only starting using her signature catch-phrase of "Spoilers!" after the Doctor used it on her the first time, having heard her use it a half dozen (or more) times before.
It was revealed that Clara's life is consumed by this. She enters the Doctor's time-stream in order to save him, making her show up numerous times in his past. After him meeting her in Asylum of the Daleks and The Snowmen, he becomes curious about what is going on and finds her in The Bells of Saint John, which leads to her travelling with the Doctor, and eventually ending up on Trenzalore with him with the opportunity to save him by jumping into his time stream. She says that she's not afraid to do it even though she knows she'll die because she's already done it—he already met her at the Dalek asylum and in Victorian London. This is despite the fact that the stars are going out and Strax is turning homicidal again, making this possibly the single most confusing exampleof time travel in the entire series.
The 12th Doctor helps save Gallifrey in The Day of the Doctor, and he was only able to exist due to the Time Lords changing history by giving the 11th Doctor a new regeneration cycle.
The Time of the Doctor reveals that most of the Eleventh Doctor's run was one of these. The Church of the Silence (among other powers) besieges the Doctor on Trenzalore in order to stop him from using a crack in reality to bring back the Time Lords. After a few centuries of this, Madame Kovarian's branch of the Silence breaks away and goes back in time to try and kill the Doctor before he ever reaches Trenzalore, setting the events of Series 5 and 6 into motion. But, their attempt to blow up the TARDIS just creates the cracks that pose such a threat, and their creation of River Song to assassinate the Doctor just results in her saving his life multiple times, which means he lives long enough to get to Trenzalore to begin with. The irony is lampshaded by the Doctor when he pieces it all together.
In Time Heist, it turns out the Doctor was hired by the future version of Madame Karabraxos to carry out the robbery she herself witnessed and free the Teller.
Steven Moffat's general love of the trope has led to the Series 8 cast in particular referring it to as "the Moffat Loop".
In the Time Travel episode of Ghostwriter, the kids in 1928 solve their case by sending Ghostwriter to 1993 to find out how the case was solved, then bring the info back and use it to solve the case. As the kids in 1993 are reading old 1928 newspapers about the case, the pages start to turn blank — if they don't send the info back, the case will never be solved and thus the newspaper will never have it.
The Sarah Connor Chronicles — Fischer only survived Judgement Day and taught the machines the things he did because he was in prison — thrown there due to his future self planting a backdoor into military computer systems, having logged in, of course, with his own retinal scan.
On the other hand, this is explicitly part of an aversion — Derek is from a future where Fischer didn't do these things, while his girlfriend Jesse is from the future Fischer contributes to (or at least a future where... oh, no, I've gone cross-eyed).
There's also the fact that Derek's primary reason for traveling to the past is to kill Andy Goode, who he thinks will contribute to the creation of SkyNet. He succeeds, but the future doesn't change, probably because Andy's computer is used to create someone to fight SkyNet.
Near-miss at the end of the second season of Heroes when Peter Petrelli almost becomes responsible for the end-of-the-world timeline he visited earlier, through his efforts to prevent it...but drops the Idiot Ball after holding tight all season, and destroys the virus.
Referenced several times in Star Trek: Deep Space Nine episode "Trials and Tribble-ations". The Temporal Investigations agents specifically loathe Stable Time Loops. Also, Bashir is hit upon by a woman who has the same name as his great-grandmother. After commenting on the fact that nobody knew his great-grandfather, he attempts to argue to O'Brien that he has to go sleep with her in order to ensure his own existence. O'Brien dismisses the notion, causing Bashir to declare that he can't wait to see the look on O'Brien's face when he finds out Bashir never existed.
Also happens in "Past Tense" where Sisko, Bashir and Dax are sent back into Earth's past and Sisko has to stand in for a civil rights leader (who died for the cause) in order to allow the Federation to exist. It is later noted how similar Sisko looks to the historical figure.
The Prophets form a part of one. Sisko meets them in 2369, informing them that they are the gods of the Bajorans. That they sent the Bajorans "Orbs". Thing is, the Prophets live in a wormhole, and exist outside of time. From their wormhole, they can simultaneously access any era of history (Shown when they bring an ancient Bajoran to the present, then take him back to his time). So the Prophets, upon being told that this is what they do... do it. They send the orbs back in time, and begin acting as gods to the ancient Bajorans, causing the culture that Sisko gets to know... and then tells them about on his first meeting.
Sisko's own existence. Sisko is the Emissary of the Prophet, and discovered the wormhole. This caused the prophets to possess Sisko's mom, so she'd marry Sisko's dad, ensuring Sisko's birth. The only reason the Prophets did this, is because they met Sisko in the future (and being outside linear time, realized the role they played in his life, and thus took it upon themselves to make it happen).
And referenced almost explicitly in the Star Trek: The Next Generation two-parter "Time's Arrow", which deals with a similar subject. It's put in as something of a Shout-Out to sci-fi fans: Samuel Clemens (aka Mark Twain) receives his own watch from the Enterprise who have time-travelled back to his period in history after recovering the watch from a cave in the future (and no, it was not made from a BOX OF SCRAPS!). The end of the two-parter concludes with Clemens in the same cave in that time period, looking at the same watch ... and, with a chuckle of amusement, putting the watch down again so the Enterprise crew will find it in the future, thereby sentencing the watch to an eternity inside one, as the watch was put there by Clemens to trigger off the loop to begin with.
Star Trek: Voyager. In "Time and Again" Voyager witnesses the destruction of a civilization. When Janeway and Paris are accidentally sent back in time a few days before the incident, it turns out that the crew's attempt to rescue them is what triggers the disaster. Fortunately Janeway stops the attempt and the timeline returns to normal.
Features prominently in the three-part episode "Future's End". Captain Braxton, from the 29th century, goes back to the 24th century in a single-passenger timeship to destroy Voyager to prevent a 29th century disaster. Voyager fights back, causing the timeship's systems to malfunction and transport both ships to Earth in the late 20th century, with Voyager arriving later. The timeship itself crashed and was scavenged by an opportunistic businessman who used its technology to jump-start the Information Age, which allowed the 29th century technology to exist so it could be scavenged...
Additionally, the businessman's attempts to travel to the 29th century to pick up more future tech would result in the catastrophe that would cause Braxton to travel back in time.
Implied during the Year of Hell arc. The captain of the ship behind the constant fluctuations in the timeline created his ship to prevent an enemy from having conquered his. While he succeeded, a plague caused by their absence wiped out his family. He continued tinkering with the timeline in an attempt to restore his family. Ultimately the timeship was destroyed, reverting the timeline to its original course... where the captain is studying to build a timeship to keep his people from being conquered.
Implied to be a broken cycle, as he puts down his notes and walks away at the end. Given that the timeship misfired and erased itself from history, odds are that the loop was broken and the ship was never built in this new timeline.
Debatable. It's one thing for the ship to erase other civilisations from history while remaining immune to changes in the timeline, but erasing itself sounds like it would cause a grandfather paradox.
In the premiere episode of Primeval, Nick Cutter discovers a human camp (and human bones) in the Permian, as well as a camera with a picture proving his vanished wife had been there. In the first season finale, having been reunited with his wife, they travel back to the Permian where Helen convinces him to take her picture...which he suddenly realizes is the picture he'd discovered previously, and that the camp they just set up is the one he'd discovered originally. An actual change does happen to the past, however, which confuses things.
They also discover a human skeleton, but Nick determines that the skeleton is that of a man. The second time around, the same soldier who escorted him the first time goes with him and is attacked and mortally wounded by a Future Predator. Before dying, the soldier realizes that it was his skeleton they found.
There's also a Medieval knight who follows a dracorex through an Anomaly on a quest to rid his village of the "dragon" and discovers that he has arrived into Hell (actually, modern-day London). Later, he finds a monument dedicated to himself and is made to realize that the monument describes his life after coming back and "killing" the dragon. He's supposed to marry the local lord's daughter and have several children. He goes back, reports the dragon dead, and kisses the lord's daughter, something he wouldn't know to do without going to the future.
In the Stargate SG-1 episode "1969," the team travels back to the title year and has to figure out how to get home, meeting a young General (then Lieutenant) Hammond, two hippies, and a young Catherine Langford. General Hammond sends a note back with them that Captain Carter is not allowed to read until after they go through the gate. The note contains cryptic instructions as to how to get home, as well as instructions from General Hammond to his younger self to help the visitors (that from his POV writing the note he has already helped). It is later revealed that General Hammond has been waiting for years for the sign that it is time to send the note (evidenced by a large cut on Captain Carter's hand).
Still on episode "1969", when the SG-1 team manage to travel back to the future, they accidentally ended up jumping several decades in the future, far from their own time, arriving on a deserted SGC. There, they meet an old Cassandra (the human girl they rescued on a planet attacked by the Goa'uld in "Singularity"), who was expecting them in order to guide SG-1's return to their time, implying that sometime between their return and her meeting with them in the future, she was told to meet them there so they could return to their time.
Some fan theories have it that this episode might be the entire reason that SG-1 exists. Hammond knew that the team had to be these specific people, because that's who he saw when they went back in time, so that's who he put on the team. Confused yet?
It might even be the reason that the whole Stargate Project exists, by getting Catherine Langford and the government interested in restarting her father's investigation of the strange artifact.
The Red Dwarf episode "Ouroboros" reveals that Lister is his own father. He left his baby self three million years in the past so that the resulting time loop would stop the human race ever truly becoming extinct.
In another episode, the crew travel back to the assassination of John F. Kennedy — and accidentally knock the assassin out of a window, killing him. To preserve events, they persuade JFK to travel forward in time and assassinate himself.
In the fifth season of LOST, John Locke may have just created one of his own: while time travelling to 1954, he tells Richard Alpert (immortal spokesman of the Others) his exact birthday, and encourages him to consider young John for a leadership role. Considering his current relationship with the Others, he may have pretty much written his own destiny.
An even bigger one occurs in "He's Our You" and "Whatever Happened, Happened": Ben torments and manipulates Sayid and others in the future. Sayid then travels back in time and shoots 12 year-old Ben, attempting to prevent Ben's later misdeeds. Kate, Sawyer, and Juliet, in order to save Ben, take him to the Others. This leads to Ben becoming the ruthless individual who later torments them, and who causes their time travel.
According to Daniel Faraday, this is how time travel in the Lost-verse works, except for Desmond for some damn reason.
In yet another loop in the fifth season, in "The Variable", Faraday himself is killed by his mother when he travels back in time to before he was born. His mother therefore knows, throughout Faraday's life, that she killed (the future) him, yet she accepts this "sacrifice" and uses every opportunity to strictly direct him along his destiny.
Also in the fifth season, Richard gives a compass to Locke, who then travels through time for a while and gives the compass to Richard in the 1950s. Where did the compass come from? Who manufactured it? Where did it go? Also shouldn't it age into dust? Perhaps it did age into dust, and Richard then created a new one which he gave to Locke and which became the same compass that had aged into dust.
Let's just say that LOST has confusing time travel. However, the clearest, unambiguous example in the show is "The Constant", in which Daniel's journal guides him to tell Desmond certain things to his past self, which his past self then records in the journal before losing his memory. Most notably, the frequency needed to make his time machine work came out of nowhere, since it was passed back and forth between Faraday and Desmond infinitely. Unless, that is, past Faraday already knew the frequency before Desmond showed up.
The plane crash itself. The Losties crashed, travelled back in time, and caused The Incident. The Incident released a large amount of electromagnetic energy, which would later be the cause of the plane crash. In other words, they caused the crash. After it had happened (from their timeline's perspective).
Stephen Colbert (circa 2009-2509 or so), the main character in The Colbert Report, failed to stop Stephen Colbert (circa 2005-2009) from electrocuting himself, then took his place as host in order to be hosting the show in 2500 to come back in time so he would exist in his present to come back in time...etc.
In Kamen Rider Kabuto, despite the fact that the Hyper Zecter was destroyed, the fact that Tendou had all ready attained it in a parallel time means he can send it back to himself from that future so he can have it to give to himself later when this time comes around. Yeah.
Lampshaded in the movie God Speed Love where Tendou gets the Hyper Zecter legitimately and uses it to go back in time to give himself his belt.
It gets better: doing so in the movie caused the show timeline to happen.
Kamen Rider Gaim has a hell of one, and it's a bit tragic. You know the mysterious woman that told Kouta what to do with the Driver, and the whole "You'll have to fight to the bitter end, until the world is dyed in your image" speech? The also-mysterious War God Gaim calls her the "Priestess of Fate," the more-mysterious-than-both-put-together DJ Sagara calls her "the Woman of the Beginning." Who is she? The reason she looks like Mai is because she is Mai. Not a brainwashed Mai, an alternate Mai, or a thing looking like Mai, it's that girl from the dance troupe. When she got the power of the Golden Fruit, she tried to change history by leading her friends away from the path that led them to where we are near the end of the season, but she hasn't perfected her control. Her messages to the past, in the ultimate example of That Came Out Wrong, were garbled and warped into the cryptic appearances of the "Woman of the Beginning" that put them on that path. On top of that, you know how Sagara knew who to support throughout all this, also having a big hand in things getting to where they are now? Sagara simply took note of who Mai approached - someone from the future felt that changing their destines would change the world, so he decided he'd keep an eye on them. Congratulations, Mai: you really are the one at the beginning who drove everyone's fate to where it is today. However, she's not through trying just yet.
In the Supernatural episode "In the Beginning," Dean's actions help to set many elements of the series in motion, from encouraging his father to purchase the Impala that Dean later drives, to accidentally focusing the attentions of the Yellow-Eyed Demon on his mother, Mary. The creator of the show noted that this concept confused Jensen Ackles a bit. He was told to just go with it. It was stated that what had happened was fate, and that Dean wouldn't have been able to change the outcome. He had been sent back just to witness the events. Which is weird, because an angel later goes back in time to try to change it all. She fails, of course, but it has nothing to do with fate.
In a cleverly done example by the writers, the season 9 episode "King of the Damned" had Big Bad Abaddon bring Crowley's only son to the future. And in the end, he stayed there Which one would at first think would screw up an earlier episode where Bobby used Crowley's dead only son to get himself out of his contract. However, when taking the events of subsequent seasons into account. Bobby was killed of for real in season 7 (in an unrelated event), long before Crowely would have claimed his soul. And it was revealed in season 8 that even if he was out of his contract, Crowley was going to take his soul to hell regardless On top of thatAbaddon kidnapped his son on the day he was going to die out in sea anyway via storm, so his disappearance didn't have any real effect on the world. So in the end, the past was manipulated with little to no affect on the present (and canon).
Fraggle Rock: Mokey, researching an ancient leader named Blundig who caused some boulders to be moved, accidentally goes back in time, pretends to be Blundig, and causes the boulders to be moved. In the process, she also makes Fraggle culture closer to what it is in the present.
The Book of Pooh has a story that's somewhat close to this trope. The story "Once Upon a Happy Ending" opens with Tigger hanging upside down in a tree with honey jars stuck to his paws. He wonders what's going on and the Narrator explains that he accidentally opened the book to the end of the story. He suggests they go back to the beginning so they can find out what happened and Tigger agrees. It turns out that in the story, Tigger is trying to help Piglet to retrieve an acorn that he lost. Along the way, he gets a couple of honey jars stuck on his paws. Eventually, he learns that retrieving Piglet's acorn would require him to climb a tree, but at this point, he says "no way" because he's already seen what happened. He backs away from the tree, but trips and ends up getting catapulted into the tree.
Lesser known TV series Crime Traveller had this where 2 police officers travelled back in time to either stop, or work out, who committed a crime. Often when this happened they had already lived the experience and then travelled back in time to relive it. In the original version of time certain things happened that were strange/funny/helpful etc and it was only when they travelled back in time that they realised it was their future selves that caused these incidents to happen.
The Dawn French comedy anthology seriesMurder Most Horrid has an episode in which French plays an inventor working on a time machine. Her simple-minded husband's behaviour becomes so erratic that she bludgeons him to death with a wrench. After serving time for his manslaughter she returns home, completes the machine and travels back to try and stop herself, only to discover that the presence of herself from the future was what caused her husband to behave so annoyingly in the first place. She was even accidentally responsible for the wrench being in just the right place for her past self to pick it up...
In Children of the Stones the village of Milbury seems to be caught in a loop where similar characters go through the same set of events again and again. At the end of the series, as Professor Brake and Matthew leave the village, Joshua Litton arrives. Litton is identical to Rafael Hendrick, who had been brainwashing the villagers. The implication is that the story is about to start again.
The "Boom Boom Machine" in Fringe originated from one. Supposedly built by the First People, the machine was actually built in the future by future versions of the main characters and sent back in time millions of years to be discovered by the present-versions of the characters, who believed it to be an ancient device created by a mysterious race known as the First People, who were humans that evolved long before the dinosaurs. The present-day characters searched for all the pieces of the machine and reassembled it in order to try and fix the damage to space-time that interdimensional travel had caused. However, when activated, the machine creates a bridge between the two universes, forcing Fringe Team and alternate-Fringe Team to work together to repair the damage.
Somewhat amusingly, future-Walter realizes that he has no choice but to send the pieces of the machine back through time in order to complete the loop, and calls attention to the fact that this represents a paradox.
Then there's the Series Finale, dealing with the Fringe team's attempts to repel the Observers-turned-Invaders. Walter accomplishes this by going forward in time to prevent a scientist from creating the Observers, so that they never travel back in time to meddle with us. Of course for this he needs the help of September, a humanized Observer now known as Donald, as well as the "defective" Observer child Michael, neither of whom should strictly speaking exist.
The Kamen Rider OOO section of Movie Taisen MEGAMAX: Kamen Rider Poseidon, the movie-exclusive villain, turns out to be Aqua, a future Rider infected with the Core and Cell Medals that were thrown into time in the series finale. What makes this an example? Prior to the time jump, Aqua was a water-based Rider...who was afraid of water. An older Kougami gives Aqua a belt with three artificial Core Medals with the promise that it will "make him into a real hero". Cue the time-space accident that transforms him into Poseidon, the time jump where he encounters Eiji and the gang who save him, and Aqua being inspired by their courage to overcome his fears to beat Poseidon. That's right, the whole thing is one big temporal Batman Gambit created by Future!Kougami.
When visiting Chicago in 1992, Darien visits the restaurant that was famous in 2192 and orders his favorite dish there: an award-winning chicken pot pie. The pie is terrible. While tracking down the fugitive of the week, he has his AI Selma look up a 22nd century celebrity cookbook to find the chicken pot pie recipe the restaurant uses in his era. Then he gives a copy to the chef right before leaving town, thus enabling the place to start winning awards, become famous, and end up serving what would become Darien's favorite dish two hundred years later.
The show can't seem to decide if the events take place in the past or a time-shifted Alternate Universe. For example, in several episodes, Darien leaves messages for his boss in the future by having Selma put ads in certain newspapers. This would clearly indicate the first version of events. However, the second version is stated many times. In fact, Darien is usually unconcerned about how his actions might affect the timeline, indicating that he knows it won't affect his future.
This is discussed in an episode where one of the escape criminals is a huge fan of a late-20th century country singer, who will be huge in the future. Right now, she is just starting out. The criminal becomes her anonymous benefactor, sending her things like a guitar and boots, that he bought in his own time and actually belonged to her. After kidnapping her, he reveals that he has recordings of all her songs, to make her life and career easier. After defeating and sending the criminal back, Darien talks to her about her future career, explaining that, since this is an alternate reality, there's no guarantee that it will be as successful as in his own past. She then leaves before telling him of a new song she thought of about him. Darien is stunned to realize that his favorite song is about him.
A rather depressing loop appears in Misfits: In Season 2 the mysterious Superhoodie turns out to be Simon, who repeatedly helps the main characters and in the end dies Taking the Bullet for Alisha. However, in Season 3, Alisha gets killed, and Simon goes back into the past to save her, but as mentioned, ends up dying for her in Season 2, long before the death that he went back in time to prevent.
In the Hercules: The Legendary Journeys episode "Once Upon A Future King", King Arthur becomes a cruel and arrogant tyrant, so Merlin sends him back to Hercules' time. Hercules, Morrigan, and Merlin's past self (Merlin is very, very old) manage to redeem him, and in the process, the past Merlin learns that he will gain magical powers. When Arthur is returned to his own time in the end, Merlin reveals that he sent Arthur to the past because he remembered what had happened and knew Hercules and friends would able to redeem him.
One of the revived The Twilight Zone episodes involved a time traveler (played by Katherine Heigl) going back in time to kill Adolf Hitler as a baby. The episode ends with her jumping into a river with the infant. Both drown. However, the Hitler's housekeeper immediately buys an infant from a homeless gypsy. The family rechristens the baby Adolf and acts as though nothing happened. It's that baby that grows up to be the monster the time traveler was trying to stop.
Space: 1999 combines this with and Revision and Dénouement. In 1999, almost 25 years after the series ended, a short Fan Film called Message From Moonbase Alpha was produced and shown at a fan convention. Actress Zienia Merton explains that moonbase systems are failing, that the Alphans have found a planet they are going to take their chances living on, and implores the people of Earth to remember them. This is revealed to be the "Meta signal" that drove the plot of the first episode.
The pilot of Eureka has Jack and Zoe drive into the titular town past on a rainy night past a car... with them leaving. This is the first clue that this town isn't normal. The season finale ends with Jack driving Zoe back to college... and passing their original selves driving in. Given the show's cancellation, we're not likely to find out which of the experiments caused this.
In the Haven episode "Sarah", Duke Crocker finds a gold doubloon among his late father Simon's belongings. When he is sent to 1955, he meets a bartender who turns out to be his grandfather Roy. Duke pays using the gold doubloon, and Roy gives it to eight-year-old Simon as a birthday present.
One episode of Quantum Leap involves Sam leaping into the body of the sidekick to the host of a children's science fiction show about time travel…who also happens to be a bit of a crackpot amateur scientist trying to invent a time machine. Sam's task is to stop him from being committed to a mental institution. Sam succeeds, and the next episode of his show sees the man get a fan letter from "Sammy B" asking how he invented time travel. The host then goes on to explain his actual theory of time travel...which, it turns out, is the same theory that Sam himself used to invent time travel and form Project Quantum Leap.
Even better? Sam taught him that theory earlier in the episode.
Zig-zagged in Farscape, in the first season, the Evil Sorcerer Maldis reads Crichton's mind and, as proof, tells him that he lost his virginity to a girl named Karen Shaw in the back of an SUV. In a much later episode, the crew ends up in 1986 trying to keep Crichton's father from going up on the Challenger on its doomed flight. Meanwhile, Chiana meets Crichton's younger self and whose name young John misinterprets as "Karen" and her "Ow!" (from touching hot metal) as "Shaw" (her blue skin is explained as part of a Halloween costume). The rest is history. So, yes, John Crichton boldly came long before he even knew aliens existed.
In an episode of Earth: Final Conflict, an archaeologist discovers a modified ID portal and a man's fossil from prehistoric times. The problem? The skeleton is that of a modern man who didn't exist at the time carbon dating established. Long story short, a medieval monk ends up traveling with Renee, chasing down a female Atavus who uses the modified ID portal to jump through time. The Atavus ends up killing him in prehistoric times, when the Atavus ruled the Earth, and cavemen were their food. Renee kills the female Atavus and impresses Howlyn before jumping back into her own time. Thus, the skeleton is that of the monk. Furthermore, the archaeologist speculates that seeing Renee in action likely caused Howlyn to try to make more humans like her using the DNA of the dead monk. If that is true, then it was their time travel into the past that ensured the existence of modern humanity.
In the early episodes of Kamen Rider Gaim, the Armored Riders are met by a strange woman in white, who bizarrely is nearly identical to one of the titular Rider's closest friends, Mai. The woman tries to warn the Riders that should they take even a single step down their current path, there's no turning back; very cryptic and ominous. As the story progresses, a secret is revealed in regards to the future of the world's fate: it's coming to an end, and only the power of an otherworldly Sacred Fruit can change it. Mai turns out to be the one to obtain the Fruit, and in doing so becomes the mysterious Woman of the Beginning. She travels back through time to warn her friends of their impending doom, but temporal distortions make it impossible to get the right words out, leading to the vague, cryptic, ominous warnings of the early episodes.
In live performances, the Flight of the Conchords song 'Bowie' is usually preceded by a description of Bret and Jermaine travelling back in time and meeting David Bowie, to whom Bret plays his Bowie's own songs, and even leaves an "easy to play Bowie song book".
The Black Sabbath song "Iron Man" is about a person who travels through time "for the future of mankind" only to find that the world is destroyed in an apocalyptic event. Deciding to return to his present to warn the people of the coming disaster, he gets "trapped in a magnetic field" which turns his skin into metal. Thus, when he warns the people of the present, they are frightened by his appearance and too afraid to listen to him. Then, out of frustration that no one heeds his warnings about the forthcoming apocalypse, he causes the apocalypse.
"One For the Vine", on the Genesis album Wind and Wuthering, tells the story of a soldier deserting from an army led by a messianic leader. The deserter finds himself on an icy waste populated by primitive people, who see him as a messenger of God. He reluctantly takes the role simply in order to help himself get home, but ends up becoming the very messiah from whom he fled. As he leads his army into battle, he sees one soldier run away from the host, and vanish...
Show Of Hands song The Bet is about a man who finds ten grand next to a car crash, takes it, bets on horses with it, wins ten grand and... yeah, you see where I'm going with this.
Possible example in the Cygnus X-1 duology by Rush: the narrator is pulled into the black hole known as Cygnus X-1, and arrives in a world ruled by the Olympian gods which may or may not be our own world in the distant past. He ends the war between Apollo and Dionysus by telling them his story. They dub him Cygnus, after the black hole through which he entered their word. He becomes a god, presumably the mythological figure the constellation Cygnus, and thus the black hole Cygnus X-1, is named after.
Loony Labyrinth and its sequel, Mad Daedalus, forms a Stable Time Loop with regards to the invention of the Loony Machine: the player travels to 2,000 B.C. with the Loony Machine, which Daedalus examines. After the player returns to the present day, Daedalus eventually (re-)invents it. However, Daedalus cannot power it because his assistant lost the Loony Stones that power it, so Daedalus places the machine in the Labyrinth. it is excavated several thousand years later, and the player finds the Loony Stones, then uses the Machine to travel back to 2,000 B.C....
The audio drama "Flip-Flop" takes this to a rather confusing extreme: Two time loops that feed each other. It's presented on two discs, a "White disc" and a "Black disc", and they can be listened to in either order (or indeed in a continuous loop), as each one follows a different timeline. To summarize: On both discs the Doctor and Mel arrive to find the planet Puxatornee on Christmas Eve just before midnight in a terrible way: On one disc, a radioactive wasteland, on the other controlled by a hostile alien species. They are forced to go back in time to prevent it, and go back to Christmas Day to find the planet worse: On one disc, controlled by an alien species, and on the other a radioactive wasteland. They are then forced to go back to Christmas Eve before they arrived, and leave just before their other selves arrive on the planet, beginning the adventure on the other disc. In essence it's two unstable time loops, each leading to the other one.
In the Companion Chronicles audio drama "Tales from the Vault", a time-release capsule in UNIT's Museum of the Strange and Unusual reveals a message from the Doctor's companion Steven Taylor warning of an alien threat. When it gets Lost In Transmission WO Charlie Sato, against the orders of Captain Ruth Matheson, tries using a related item in the Vault to get more information in the process releasing the alien threat. After it's been defeated, he asks Matheson why the time-release capsule had opened today in the first place. She replies that the Doctor presumably read the report she's about to write.
The Companion Chronicles drama "Return of the Rocket Men" begins with Steven on his twenty-first birthday, being tortured to death for fun by a Space Pirate before being unexpectedly saved by another pirate named Ramirez, who he then sees get shot by his Bad Boss. Older, experienced and now travelling with the Doctor, he ends up unexpectedly on the same planet on the same day, ends up in the suit belonging to Ramirez, and realises he now has to save his own younger self, even if it means him getting killed.
Continuum is an RPG where the characters' entire goal is to make sure stable time loops work out.
Planescape's Faction War features a double time loop. Considering that the person stuck in it tried to overthrow the Lady of Pain, he had it easy.
Rulified by the German RPG The Dark Eye in which time travel follows a simple law: you cannot change the past, as it had already happened and you'll just end up doing what you did to create the present you're currently living in. If by some chance the hero does discover some hopelessly contradicting action, be prepared for time to heal itself. Oh, and the universe has wardens against such misuse, too.
Bizarre version from Warhammer 40,000. An Imperial warship picks up a distress call from an Imperial vessel under heavy attack, and goes to respond. When it arrives, it finds no Imperial ship, but the warship itself comes under heavy attack... and sends out a distress call. Thanks to the ability of the Warp to mess with time, the ship went to its destruction answering its own distress call.
Another example is of the ork warlord Grizgutz and his army who, after setting off into the warp, arrives shortly before they left off and decides to hunt down and kill his previous self so he can own a spare of his favourite gun. The confusion results in the war-band being stopped in it's tracks.
Singularity plays around with this trope. All those tracks that tell you where to go next? Guess who laid them. Your ultimate goal ends up being breaking yourself from the infernal, stable time loop for good.
Achron has time travel as a major gameplay mechanic so you can set these up yourself. The most common example is to create a base and have it produce an army, then have you opponent attack your base before it builds the army. You can then defend your base by sending back the units that it built in the future. In the final timeline your base survived because it was defended by units from the future, and your units exist because the base survived to produce them.
You can even get an even more immediate time loop by sending a mech back in time using a chronoporter. Then, you undo the original build order for the chronoporter and before time catches up, you let the mech build a chronoporter at about the same place. Because the chronoport (the action of sending a unit back in time) is bound to the unit and independent of the chronoporter, the mech will then travel back in time with the chronoporter it just built to build the chronoporter to be sent back in time.
Amusingly, a Grekim unit can also literally become its own grandfather.
In Sonic the Hedgehog (2006) Princess Elise has a Chaos Emerald as a lucky charm. She loses it and it's found by Silver. Silver goes back in time and gives it to her. The problem? It doesn't exist before Elise gets it, or after Silver goes back in time, and it's never created or destroyed. Also, it means the Earth should have been destroyed by the other Final Bosses.
Of course, the events of the entire game were erased from existence in the end, so yeah.
And this would have stopped them from being dangerous — Super Sonic wasn't used until after 1996 anyway, so it wouldn't matter, and after it was used, the Final Bosses came from Eggman's emerald collecting.
Actually, the world would still have been screwed. The Black Arms would have taken over anyway, and it took the Eclipse Cannon — which in itself requires all 7 Emeralds to be at full power — to destroy the Black Comet and stop the invasion.
Actually, no. Nothing ever implies that the blue Chaos Emerald originally came from the future. It was always in the past. Leaving the blue Chaos Emerald in the past would make it so that there were two blue Chaos Emeralds up until the point when Silver went back in time with it. This would also mean that there were eight emeralds until that point if not for another problem: Shadow and Silver took the gray emerald from the past, thus removing it from the timeline until the point in the future they took it to. This means that there were two blue emeralds and no gray one in the past and both a blue one and gray one in the present. Then Silver takes two of the emeralds further into the future to his time. More could be said about this, but it'd take way too long and it'd get way too confusing.
Generations implies a slightly more subtle one depending on how far you read into the aftereffects of the game's time travel plot. At the very least, Classic Sonic learns the Homing Attack by watching his future self perform it. Additionally, the 3DS version has Classic Sonic picking up the Sonic Boost from Modern Sonic.
In Ocarina of Time, Link meets a man in the future who is angry that someone in the past used the Song of Storms to wreck his windmill. This teaches Link the Song of Storms, and he goes back in time to use it and wreck said windmill.
Meanwhile, Oracle of Ages has quite a few of them, such as defeating the Great Moblin in the present and receiving a Bomb Flower as a reward, then giving said Bomb Flower to the Gorons in the past, who use it to destroy the rocks that collapsed on the Goron Elder while also promising to use its seeds to grow the patch of bomb flowers that the Great Moblin had taken control of in the present.
Subverted by the ending of Ocarina of Time. The Time Loop that would have resulted here was so incredibly unstable that the timeline split instead. Now we have 2 universes, one leading into The Wind Waker and the other one leading into Twilight Princess. Yeah, it's even more Mind Screw than the actual Stable Timeloops.
In Escape from Monkey Island, there is a puzzle in which you must navigate Guybrush Threepwood through a swamp with time-bending properties. About half way through, Guybrush meets his future self on the other side of a fence. The two of you have a conversation which ends in your future self giving you a few (apparently useful) items and going on his way. Later, when you're on the other side of the fence, you must recreate the conversation you had with your future self with your past self, give him the items your future self gave you, then go on your way. If you get it wrong, you cause a time paradox and have to start over.
A fun part is occasionally, you may be given a gun by your future self. You can use the gun to shoot your future self and carry on as normal. Of course, when you meet your past self, you yourself will eventually be shot.
Also, this means that those objects that Guybrush keeps giving to his past self in each iteration have always existed.
In Prince of Persia: Warrior Within, the Prince continuously encounters a strange creature through his travels. As it turns out, the strange creature is actually the Prince himself, transformed into "The Sand Wraith" after he found the mythical mask that could be used to change his fate, he then had to go back in time and meet his past self in all those locations. The kicker? The last time the two meet, instead of The Sand Wraith dying, which happened the first time you saw it, this time you kill your past self and resume the story in the same part as your past self, but you're really your future self. Get it?
The main plot uses this as well. The Prince goes back in time to kill the Empress before she can create the Sands of Time, not realizing that killing her is what creates the Sands in the first place. Thus, the Sands exist because the Prince went back in time, but the Prince went back in time BECAUSE of the Sands, which would never have existed if he gone back in time, which is how the Sands were created, and so on and so on. This leaves the player wondering which event caused which?
Legacy of Kain: Soul Reaver 2 seems to have one. Once Raziel finds the Reaver broken in half and sticks it back together, he threatens Morbius with it, but for no particular reason throws it away. The most logical thing for Morbius was to take the fixed Reaver, and give it to William back in Blood Omen 1. Then Kain makes two Reavers meet, creating a Time Paradox, which breaks William's Reaver. The broken Reaver is left on William's grave, thus a loop is established. There are actually more of these, but this loop is special, considering that the second Soul Reaver appeared out of nowhere.
Fallout 1 has the Player Character trying to find water for Vault 13 after its water chip is broken. It ends with the PC staying in the post-apocalyptic Earth and heading off to start a new life. Fallout 2 has a random encounter in which the player, now controlling a descendant of the character in the first game, travels back in time to just before the first game and ends up in Vault 13. The only way to return to your own time involves breaking the Vault's water chip...
This is essential to the plot of Final Fantasy VIII. Because the main party kills Ultimecia in a partially time-compressed realm, she is able to give her powers to Edea, thirteen years in the game's past, before she perishes. This is what makes Edea the perfect choice to possess for Ultimecia's plans, and causes the main conflict in the present that leads to the need to destroy Ultimecia. Additionally, after Edea inherits Ultimecia's powers in the past, the present-day Squall explains the concept of SeeD to her, thus inspiring the creation of the mercenary organization he grew up in and setting up his own role in the events of the game. The Stable Time Loop is further illustrated by the futile efforts at one of the cast members to Set Right What Once Went Wrong; she ultimately concludes that the past cannot be changed.
Strangely enough, this trope is seen in the original, Final Fantasy I. The story begins when the Light Warriors are sent to the nearby Temple of Chaos to kill the renegade knight Garland. As Garland is dying, the four Elemental Fiends of the game magically send him two thousand years into the past, when he becomes the demon Chaos, and sends the four Fiends to the still-the-past future to seize control of the four Elemental Orbs. The Fiends take roughly four hundred years to obtain all the Orbs and use them to wreck the world until the present day, when the Light Warriors fight Garland, slay the Fiends, and travel to the past to confront Chaos and die fighting him. The game ends when the Light Warriors kill Chaos and end the stable time loop.
Final Fantasy XIII-2: Small-time example in the form of Dajh naming the chocobo chick "Chocolina". He named her after the quirky merchant of the same name. Where did she get her name from? Dajh, because she is the chick. She just happens to exist everywhere and at every moment in time, because she asked Etro for the ability to help Serah and Noel anywhere (and anywhen) during their journey.
In Final Fantasy Legend III the party is warned by their Elder that people in the Past are looking for the Talon Units. In said Past they meet the said Elder and ask where they can find Talon Units. Past Elder also is thinking about naming a town and asks for a name.
An odd example from Final Fantasy Crystal Chronicles: Echoes of Time: A thousand years before the game starts, a shockwave from the future causes all the crystals to vanish from the world. Larkeicus, the villain of the story, gained immortality from these crystals and also used them to develop crystal-powered technology that he build an entire civilization upon, which naturally fell apart when the crystals vanished. A thousand years later, Larkeicus enacts a plot to build a tower as part of his scheme to prevent the shockwave that caused the crystals to vanish. Turns out the tower he built was the cause of the shockwave in the first place.
Shadow Hearts: Covenant ends with the character Karin Koenig being sent back in time some 25 years as a result of her journeys with the main character, Yuri Hyuga. There, the first person she meets is Yuri's father, and it's strongly implied that she goes on to become Yuri's mother.
And this raises the question of where Anne's Cross came from.
In the good ending, Yuri kills himself, letting himself be impaled on a rock spire, to avoid having his soul destroyed by the Mistletoe's curse. With his last thought, he sends himself back to the beginning of the first game. As he waits for the train, there are hints that this time he will save Alice from what killed her the first time.
Regarding that good ending, Yuri actually seems aware of the stable time loop ("Here comes that train again."), which raises questions of its own.
Soul Nomad & the World Eaters features one of the most bizarre examples of this trope: During an early cutscene during a New Game+, possession of a certain item sends Gig and the main character 250 years back in time, to shortly after Lord Median killed the Master of Death, Vigilance (the previous incarnation of Gig). The pair of you destroy Median's armies and cause the Master of Life, Virtuous, to murder Median, causing the fall of Median's empire that is a part of your own timeline's backstory (and giving Virtuous the idea for fusing the main character and Gig 250 years in the future). When the main character later dies, his or her soul, as well as Gig's, is sent to Drazil, who causes the original creation of Gig from the newly deceased Vigilance. Drazil then turns the two of you into two of the world eaters that are subsequently sent back to Haephnes with the newly minted Gig to cause mass destruction — which are destroyed by the main character and Gig 250 years later during the game's main storyline. Thus, the alternate timeline version of you two not only set in motion the events of the main story and are inspirations for your own creation, but also become two of your own worst enemies, and get killed by yourselves. Whew.
Not only bizarre, but also Squick of possibly Selfcest overlapping with Foe Yay/Ho Yay. In one of the ending where you play as the heroine, you basically travel the world together with one of the aforementioned World Eaters, romance subtext included. It's still vague whose soul becomes whom (fans generally assume Gig became Raksha while Revya became Thuris, but another theory is that Drazil waited the two souls to fuse together before splitting them apart. So you get either you romancing a half of your reincarnated alternate-dimension self or you romancing your reincarnated alternate-dimension partner, but you can call him Gig. But, hey, at least it proves that even Gigcan love!
The Jak and Daxter series is basically one big stable time loop, with the first two games being both prequels and sequels to each other. At the end of the first game, Jak discovers a huge portal through time. When activated at the start of the second game it unleashes the Metal Head race into the world, and Jak and Daxter are immediately sent to the distant future. There Jak discovers that he was actually born in the future, and helps his younger self go back into the past to be raised safe from harm so that he can become his old self and defeat the Metal Head leader.
The vehicle they used to ride through the huge portal was created by Keira in the future based on the specifications of the vehicle she found in the past — which is the vehicle from the future.
The end of the second stage and the beginning of the eighth stage of Gradius V are both set in the same timeframe and same battleship, with the past and present versions of the Vic Viper running through segments of the stage alongside each other. The game records the actions of your 'past' version to replay in the second run-through.
TimeSplitters: Future Perfect had numerous examples of this. One of the earliest examples is also one of the most memorable — you are given a key by your future self that you need to progress, and later pass the key on to your past self, leaving its initial existence unexplained.
As well in the You Genius U-Genix, when you find Dr. Crow, Cortez explains the entire plot of eternal life to the main villain before the main villain has any chance to learn about it. Cortez seems to believe this is a version of Dr. Crow from the future, not knowing it was the only Dr. Crow that had not learned of the plot yet, effectively kick-starting the problem. Of course, younger Crow shows up only moments later, but Crow has already learned of the plan for eternal life, removing the necessity of younger Crow to explain it, and leaves with younger Crow's time machine. Cortez then shouts "DAMMIT!" at the top of his lungs, having it be loud enough to transcend time (he is in 2240, and it is heard in 1960 by Harry Tipper).
Sam and Max Season 2 has the player create at least two stable time loops. The first involves taking a boxing glove from a character's present self and giving it to his past self — one would initially assume that the boxing glove is the same one from Season 1, but it can't be, since it turns out to be on an infinite loop. The other time loop involves traveling into the near future — so near as to be the next episode — and picking up an object, which causes the player character to be interrupted by someone calling from outside the window, asking for that object. The player character automatically tosses him the object, and receives another in return. In the next episode, the player character becomes the person outside the window, and must do what he remembers he did — an action that makes no sense without prior knowledge, even to the game's player.
Then, in Season 3, Sam and Max have to use the astral projector from the Devil's Toybox to alter the actions of their ancestors Sameth and Maximus, to get the Devil's Toybox from Egypt and into the basement where they found it. The only way Sameth and Maximus did it in the first place was with information they wouldn't know at the time; not getting the box would probably destroy the universe.
There are other things. How do you know that the vampire elf needs to bite Jurgen the Vampire Hunter in the past? Because you've met Jurgen before in the present, as a vampire.
The InfocomAdventure GameSorcerer features one. At one point, your future self appears and gives you the combination to a locked door, and demands your spell book. After you've unlocked the door, you have to travel back in time and give the combination to your past self, and get the spell book from him. (You can't carry anything with you when you go back in time.) The time travel spell is named "golmac" as a Shout-Out to the "gold machine", the time machine in Zork III. It's fun to do silly things like screaming or singing when your future self appears, then watch how they're described when it's your past self doing them.
Its sequel, Spellbreaker, features a two-in-one: you have to establish two Stable Time Loops in two different locations (with time limits on each), or else be wrung from existence by the ensuing paradox should you try to leave the hourglass. Early on in the game, you find a magic zipper that functions as your Bag of Holding; going back to that location in the past, you find a sack in its place, and have to swap the two (and all the contents thereof) before the rising water kills you. Elsewhere, there's a disused cell containing a moldy spellbook, entirely illegible save for one useful spell; when you return there in the past, you have to put your spellbook where you found the moldy one in the future (memorizing as many spells from it as you can first!) and leave the room precisely as it was (or will be) before the guards arrive.
Near the beginning of Tomb Raider Legend there is a flashback to Lara's childhood in which she set off an ancient device. Her mother then pushed Lara out of the way, looked into a ball of light and had a confused conversation with a mysterious figure (who the players can't see or hear) before disappearing. At the end of the game Lara inadvertently opens up a time portal and it is revealed that she was the person her mother was talking to at the start.
In Vandal Hearts, the NPC Leena is sent back in time, and is then revealed to be the party member Eleni, who had Easy Amnesia until that point. The loop aspect comes in with the character's pendant, given to the earlier version by the later version.
This trope is brought up tragically in Wild ARMs 5, where it is revealed that heroine Avril is stuck in one of these. She is forced to continually travel 1,000 years into the past to set in motion the events of the game... but not before she sets herself up to awaken during this time period so she can ensure things play out how they should, and she is sent to the past once again. She can never leave this loop, as it may have cataclysmic consequences, and she'd much prefer her beloved to be happy. Although all the traveling and slumber gives her Laser-Guided Amnesia, she always remembers everything before she makes her Heroic Sacrifice.
The plot of Taiyo no Shinden Asteka II (a.k.a. Tombs and Treasure) is that the player characters are searching for Professor Imes, who went missing while exploring the ruins of Chichen Itza. One of the ruins is "The Tomb of the High Priest". The ending reveals that the professor went back in time and became the High Priest.
An unusual example in Ōkami, where the protagonist's past self, Shiranui, travels to the future. She saves Amaterasu and friends from a spell that holds them motionless and Ammy was too weak to break, but at the cost of a mortal wound. She returns to the past, dies, and is sealed. When she's awakened as Amaterasu, her powers are considerably weakened, which is why she needed to be saved in the first place.
Then one in Ōkamiden. Chibiterasu meets the mermaid character early in the game and she mentions that she knows Chibi from somewhere, but he sure doesn't. Later in the game, you travel back in time and Chibi runs into the mermaid again, but this time he knows her and she doesn't know him. They separate and she doesn't interact with Chibi until the time they met before/would meet next.
The indie game Original War is all about this, with the Americans and Russians sending soldiers into the distant past to fight over the game's Phlebotinum. Whoever wins the war keeps the Phlebotinum, but near the end of the Cold War the losers send a strike force back in time to steal it...
The InfocomInteractive Fiction game Trinity contains both a major and a minor loop. The minor one involves an umbrella lost by a woman in London that you retrieve; when you go back in time to just before the bomb is dropped on Nagasaki, you give the umbrella to a girl, who will grow up into the woman you met in London. The entire game is one; you go back in time to sabotage the Trinity test (which would've powerful enough to have destroyed most of New Mexico,) create a Temporal Paradox because without atomic weapons, you would have never been born, so the universe resolves the paradox by making a small explosion every time an atomic weapon is detonated, and the game ends with you repeating your actions in the beginning.
"Small" explosion being a relative thing of course. They still are enough to take out a city — in other words, the main character in Trinity stops the creation of a superweapon that could destroy a whole state and instead creates the 'smaller' atomic weapons that still are quite powerful.
Chrono Trigger's entire plot is concerned with a bunch of stable and unstable time loops. One that carefully averts the paradox element is when Crono dies and is completely vaporized by Lavos. Later his friends save him by going back to the moment in time just before he dies to replace him with a lifeless clone. This is not a paradox because they don't alter what anyone in the past witnessed and so don't inadvertently cancel their own actions. Most of the other time loops are not resolved so immaculately. Needless to say, this causes problems.
Sunset Over Imdahl, a freeware game made with RPG Maker, contains such a loop the plague, the one that killed all of your loved ones, the one that you were sent back to try to stop? You were the carrier. A chill's running a marathon down your spine, isn't it?
In Bookworm Adventures Volume 2, EviLex doesn't exist at all, but in reality is a time travelling Lex. It was orchestrated by Bigger Brother to keep Lex busy and to get Lex to give him the Magic Pen.
In City of Heroes, the Menders of Ouroboros are a time-travelling group dedicated to keeping the timestream straight. The first one you meet accidentally creates a stable time loop when he rambles on about how you and he solved a problem in a mission you haven't undertaken yet.
Xenosaga: THE ENTIRE UNIVERSE is one of these, put in motion by Big Bad Wilhelm to prevent the destruction of the universe.
Present in the OEL Visual NovelMirai Imouto. Misaki travels from the future to the present, and tries to find a way to prevent her brother, Hiseo, from dying due to his heart condition. One of the reasons she wants to prevent his death so much is because in her past (the story's present), her brother spent most of his time before his death with some random girl (future-Misaki), and present-Misaki grew up into future-Misaki remembering that she wasn't able to spend much time with Hiseo before he died.
In Breath of Fire I, Nina is accidentally catapulted back in time. Before this occurs, Ryu and the others can meet a winged girl with amnesia who looks strikingly like an older version of Nina... After she vanishes, they can jog her memory and re-recruit her.
Chzo Mythos: The Man in Red's reason for existing is to ensure reality maintains a stable time loop.
In BlazBlue, the attack of The Black Beast in 2100 A.D. nearly destroyed the world until Nox Nyctores weaponry was developed to fight it. Then in 2199 A.D. One of these Nox, Murakumo fuses with Ragna The Bloodedge, creating The Black Beast, which is pulled back in time to 2100 A.D.
The other half ot the Black Beast is equally paradoxical: The Black Beast's existence requires the fusion of Ragna and Nu's Azure Grimoires. Ragna's Azure came from the remains of the Black Beast.
In the prequel novel Phase 0 it's revealed that the time displaced Ragna sans memory is the original hero "Bloodedge". Ragna only calls himself "Ragna the Bloodedge" to honor the name of that hero, whose sword and coat he inherited. Also, the only reason Mitsuyoshi calls himself Jubei in the present is because Ragna kept calling him that. After Ragna died fighting against the Black Beast, Mitsuyoshi took the name Jubei in honor of his fallen friend.
Yet another one was introduced in Extend, but whereas the above had some benefit to Yuuki Terumi when it finally broke, this one was explicitly created trying to prevent it from manifesting, and its existence is, to him, purely detrimental. When Terumi tried to assassinate Jin Kisaragi in Kagutsuchi in another world, Makoto Nanaya interfered in the hit and grilled him for his plans regarding Jin, Tsubaki, and Noel — the latter of which does not exist in this world. In his and Relius' attempt to eliminate her, she winds up asking Kokonoe and, later, Tsubaki about the aforementioned nonexistent Noel, which ultimately fucks everything up in that world. In subsequent worlds, Terumi tries to keep her from making things worse for him by sending her to Ibukido, but it's only when the first loop breaks that she arrives... and investigates the Ibukido cauldron. No points for guessing what she does next. Ain't hindsight a bitch?
The key to Karazhan used by players in World of Warcraft is acquired when they perpetuate a stable time loop centered on an object. After collecting the fragments of Khadgar's broken key, they take it to Medivh to be repaired. Medivh cannot immediately repair it and so instead gives the player a spare; the key he is repairing will be given to Khadgar to be broken in the future and collected by the players to be repaired by Medivh yet again.
The entire point of the quests in the Caverns of Time is to ensure that time remains stable. The Infinite Dragonflight are doing their best to change the history of Azeroth for their own ends and it's up to you to stop them. Canonically you are victorious and their efforts are ultimately futile.
There is a quest in the Dragonblight where Chromie sends you to Nozdormu's shrine to help him against the Inifinite Dragonflight, and during the fight, your future self appears to help you. The next quest is to go back and fight that same battle again, this time with you helping your past self. Don't ask how it's supposed to work out if you choose to complete the first quest but not the second...
"No wonder I started drinking."
In the finale of Cataclysm, Nozdormu, the leader of the Bronze Dragonflight attempts to send the player back in time 10,000 years but finds his powers blocked by an Infinite Dragon in the future named Murozond. The sequence of events after Murozond's defeat eventually leads to Deathwing's destruction and Nozdormu (and his fellow Dragon Aspects) becoming mortal. Then, in an effort to subvert his mortality, Nozdormu becomes Murozond and interferes with his past self so that the events leading to his depowering never happen. As Nozdormu says once the players slay Murozond:
Still, in time, I will... fall to madness. And you, heroes... will vanquish me. The cycle will repeat. So it goes.
In Dragon Quest V: The Hero as a kid meets up a young man in Whealbrook who interested in seeing the Gold Orb you're carrying. The said orb later to be destroyed by Ladja before the first Time Skip. You learn that the Gold Orb is needed to raise the Zenithian Castle to the skies from underwater. You then visit the fairy castle, travel back in time using the mirror, find your younger self, and switch the decoy orb with the Gold Orb. The orb Ladja destroyed was a fake, and the young man early in Whaelbrook was your older self.
In RuneScape, this is part of how the quest "Recipe For Disaster" works. Specifically, in the Evil Dave subquest, when you have to make various soups, then have Dave taste-test them, even though to his perspective, the events of the quest happened earlier. When you step into the time-field to give Dave his soup, the player tells Dave specifically to remember how it tastes.
In SpellforceRohan is both the Big Bad and Big Good of the game thanks to this. As a young man, he travels forward in time, kills his elder self and attempts to recreate The Convocation, a spell which nearly destroyed the world the last time it was cast. As he grows older, he has a Heel-Face Turn, and travels back in time in an attempt to repair the world. In that time he becomes embroiled in the plot to stop his younger self's schemes, setting in motion the events which lead to his own murder.
There seems to be one in The Witcher: The magical boy Alvin shows the ability to teleport himself to safety when in great dangers, but not having direct control over where he appears several times during the game. The last time he simply vanishes and is never heard of again. However, the Grand Master and founder of the Flaming Rose order seems to know Geralt way and repeats words that he had said to Alvin before he disappeared. He also has the same amulet as Alvin does, but it appears much older and worn. Apparently Alvin not only teleported through space but also time and his experiences during the war between the Knights of the Flaming Rose and the elves inspired him to found the Order in the past.
In DoDonPachi: DaiFukkatsu, EXY, at the end of DoDonPachi dai ou jou, tries to go back in time to prevent the Blissful Death Wars—that is, the events of DOJ, and destroy the cause of the wars. Not only does she fail, but in doing this, she also causes the Blissful Death Wars in the first place! If there's any saving grace in all this (due to the unclear meaning of the ending monologue), it's that your fighting simply prevented the wars from degrading into something even worse.
In Bastion, activating the Bastion's Restoration Protocol rewinds time. But it doesn't allow Rucks, Zia, Zulf, or The Kid to stop the Calamity from happening again. So it happens again.Fridge Horror sets in when you realize how many loops it might go (or have been) through before something could change and lead to The Kid activating the Evacuation Protocol instead.
No time to explain You are watching tv when yourself from the future, with armor and a laser gun, bursts through your wall. He is dragged away by a giant lobster, and drops his laser gun. You use it to save him. When you defeat the giant lobster (and included alien mothership), yourself from the future gives you his armor, and tells you to go into the time warp and warn yourself from the past. You do. And are dragged away by a giant lobster. Guess who tries to save you...?
Escape From St Marys: Your explorations from the school reveal various cases of vandalism. When you go to the past, you turn out to be responsible for every one of them.
Kingdom Hearts 3D [Dream Drop Distance] has one in the form of a Start of Darkness. (Heh.) Xehanort's heartless, the Big Bad of the first game goes back in time and brings his teenaged self to the future to witness and aid his older selves' variousevilplots. When he returns to his own time period, his conscious mind will not remember what he learned, but the knowledge will be embedded in his heart, driving him to take the actions that will lead him to that future.
Bioshock Infinite subverts this in that the Lueteces help Booker to eventually break the loop and reset the multiverse by leading him to kill himself at a pivotal point in time.
Notably, only the Booker who has accepted the Baptism and is on his way to becoming Comstock is killed, thus letting the Booker who did not accept it go on with his life, not selling his daughter.
The remake of Space Quest: The Sarien Encounter adds a brief scene after your character steals a spaceship, showing some sort of pod materializing where the ship was a few seconds ago. This pod is actually a Time Machine that your character uses in Space Quest IV: Roger Wilco and the Time Rippers, and one of the places he uses it to go to is the first game (where a bunch of monochromatic bikers dis him for being pretentious with his 256 colors). Also, at the start of Space Quest IV, a young man who introduces himself as your son from Space Quest XII saves your life. In Space Quest V, you meet the woman who matches the picture of his mother he shows you at the end of Space Quest IV. If you get her killed, you will be retroactively erased from existence, as she died before being able to give birth to your son.
Episode "Klingon War", missions "City on the Edge of Never" and "Past Imperfect". This is Cryptic's explanation for the part of the prophecy of the Kuvah'magh that says "You will follow in my footsteps before I have made them." Ambassador B'Vat kidnaps Miral Paris and takes her back in time so that he can use her blended human/Klingon DNA to cure the Augment virus afflicting the Klingons and get them their ridges back. This leads to the Klingons becoming War Hawks again, leading to the current war, which leads to B'Vat's shenanigans.
The Foundry mission "Relics" has you rescue a Human Popsicle, teach him the sun-centric model of the universe, and send him back to his own time, where he instructs Copernicus on the model, allowing humanity to explore space, form the Federation, and let you rescue the Human Popsicle.
The Foundry mission "Divide ut Regnes", a Fix Fic for the much-maligned official mission "Divide et Impera", has you setting out to fulfill one by traveling back in time to just after the mission. You snatch the Undine impersonating Admiral Zelle, she takes a head injury, and you drop the catatonic Undine off at Admiral T'nae's office. All this to explain some Gameplay and Story Segregation, i.e. why Admiral Zelle is still standing there after going with you on the mission and infiltrating the Romulan Star Navy.
In Robopon, Cody is the one that saves Majiko and the world from Dr. Zero, Sr., in the second game, about twenty years before the events of the first. The younger versions of Zero Sr.'s children, Zero and Zeke, are present to see their father (and the older Zero Jr.) defeated. Dr. Zero Jr., then became an evil scientist to live up to his family name, which in turn is responsible for bringing him into conflict with Cody in the first game. When the end of the second game comes along, Cody fights and defeats Dr. Zero Jr., followed by Dr. Zero Sr. shortly afterwards, with the young Zero and Zeke present.
Of all places, Billy vs. SNAKEMAN has one when you reach the later stages of the Hero's Quest. There's a reason the process that adds one to your Season count is called "Looping" - every playthrough of the story is one of these. The events of Pierce the Heavens begin with you breaking the most recent loop.
In Ever17, the main character (revealed to actually be a 4th-dimensional being known as "Blick Winkel") travels back in time from 2034 to 2017 to save two other characters from certain death, only to find that if he immediately reveals their survival to the others, that will create a Temporal Paradox preventing him from coming back in time in the first place—so instead he is forced to hide their existence and manipulate the others into setting up the event in 2034 that results in him being "summoned" in the first place.
Fate/stay night. The swords that Archer carries. Shirou can only create a weapon he's seen (most of the swords created in Unlimited Blade Works come from weapons he saw in Gilgamesh's Noble Phantasm, Gates of Babylon.) However, in the case of his two main swords, Shirou learned to create them from seeing his future self wielding them.
Also subverted: Shirou doesn't have to become Archer in the future for this to be valid; he just has to see the swords. In other words, whether or not it is a stable time loop is less important than the fact that it could be.
In Nine Hours, Nine Persons, Nine Doors, this is one possible interpretation of the ending: Akane worked her way through the Nonary Game 9 years in the past, transmitting the answers into Junpei in a possible future. When she reaches a puzzle she can't solve, she explores through possible futures until she figures out how to lead Junpei into one where he faces the same puzzle. He's able to solve it, and transmit the answer back to her, allowing her to avert her own death. But after this incident, she has to set up the second Nonary Game that Junpei finds himself in 9 years later, completing the loop. (The alternative theory is that Santa is trying to Set Right What Once Went Wrong, while Akane is projecting an image of herself into the future throughout the first game.)
Its sequel, Virtue's Last Reward, seems to be setting this up as well. There are at least two. The first occurs in the path where the old woman does not die — upon nearing the end of the path to Phi's ending, Sigma and Phi go back in time and save her, thereby setting up the timeline in which she lives. The second one is the cycle Sigma and Phi are going though, as explained by the diagram in the true ending route. However, the characters are actively trying to break the stable time loop, which is why they set it up in the first place.
The DS game Time Hollow is rife with these, mostly because more than one person can adjust time.
In all reality, the entire game is one BIG Time Loop which is both stable and constantly shifting. The overarching plot is one huge example due to the protagonist sending himself hints and clues at the end of the game to his startgame self but the events of both the past and present during certain periods is in constant flux, even though due to the looping nature, that flux is always in its own stable loop.
In this hilarious xkcd comic, Hitler is actually killed. However, the man who kills him only goes back to 1945, and murders him in his bunker at the end of the war.
In the Dominic Deegan, Oracle For Hire arc "The Storm of Souls", Dominic researches the creation and death of the first Acibek at the advice of Klo Tark, who met Dominic for the first time when he saw him several thousand years ago watching the death of Acibek.
In Wicked Powered, time travel incidents result in the protagonist being his own father AND his own mother.
In Stickman and Cube, Cube purchases a time machine on eBay. The time machine then travels to the future by itself, and when it returns, Cube sends it back. Through time. To before they bought it. The guy who sold them the time machine finds it, and, having no other use for it, puts it on eBay...
In probably one of the shortest and most succinct versions of the trope, Fuzzy of Sam and Fuzzy engages in a Stable Time Loop in this strip.
Not quite as short as this one from 8-Bit Theater where Black Mage witnesses himself saying something in the future, wonders out loud why he will say it, and then says it in response to Red Mage's explanation in the space of three "panels". In the following strip, Red Mage raises the question of where these words are actually coming from. "Information cannot erupt into being from nothingness! It's a paradox!"
Equally as short is this Faulty Logic page, on why you shouldn't rob your future self.
Here's another8-Bit Theater example. In a previous comic, Thief stole his class change from his future self. In the linked strip, the other three Light Warriors get their class changes reversed while fighting Sarda. Thief remarks on how that "worked out okay." Cue his class change getting stolen by his past self.
Thief: Well. I deserve this.
Sarda: What you deserve is so much worse.
8-Bit Theater is revealed to be one giant time loop. Here's how it goes; A child named Sarda loses his family and is traumatized- several times- by Black Mage and the Light Warriors. Sarda grows up to be the most powerful wizard in existence, and uses his power to go back to the beginning of the universe to become its master and prevent the Light Warriors from existing. When he gets there, a White Mage beat him to it and now the universe obeys her commands, with Sarda stuck in the past. As the world forms around him, Sarda vows to keep White Mage from going back by putting her into a pocket dimension- which turns out to be the universe's birth. Meanwhile, Sarda decides to send the Light Warriors on quests so that they become heroes of legend, and when they're at their strongest, destroy them for added humiliation, and in doing so they cause many of the trauma kid Sarda experienced. As Red Mage points out, Sarda is just as responsible for his suffering as they are, as he could have stopped them beforehand. He retorts with;
Sarda: No one can unmake the past. It's already happened, there's no "undo". Similarly, the future already happened. we just haven't reached it yet.
Black Mage: Okay, I have a theory. It's called: I never knew it possible to care less about time travel.
The party is so baffled by the logic of the situation, that Black Mage just tries to blast him into oblivion and no one tries to argue further with the logic.
Sarda assumes that changing history is impossible out of sheer ego: he tried it once and failed, so that has to be just because nobody could possibly do it, rather than because he personally made a mistake.
The ultimate fate of Unicornmotorcycle Sparkelord in The Adventures of Dr. McNinja, as he is thrown into a portal that strips him of his memories and sends him into a pyramid, where he is discovered by the antiques dealer who first rode him at the beginning of the comic, takes up with Dr. McNinja again, is thrown back in the portal, and repeat.
Sparklelord is unique in that he's half-unicorn exiled from another dimension, half-motorcycle stuck in a time loop. Something like that, anyway.
It's pretty safe to say that the majority of the plot of Homestuck is built out of Stable Time Loops, both intentionally and accidentally created. To describe all of them would probably take up most of this page.
See the Time shenanigans page on the MSPA Wiki (massive spoilers). The most prominent examples being John receiving the same bunny for his birthday thrice, and an ectobiology session where John basically creates himself, his friends, and their guardians, who are sent to Earth at different points of time by meteor-defense-portal-displacement.
Best of all, the latter actually leads to the former. After Dave gives John the first bunny, John gives it to baby Rose, who fixes it with her sewing needles thirteen years into the future and gives it back to John, who then gives it to baby Jade. Jade has it taken from her accidentally by an Alternate Universe version of her grandfather, named Jake. He then fixes it up again, and tunes it up to be incredibly dangerous, before sending it back to her. It gets waylaid on the way, allowing Jack Noir to take it and use the Black Queens Ring of Orbs Fourfold horribly mess up John's session. The bunny eventually gets back to John a third time, just in time tosave him fromJack Noir, but not before things become so irreparably damaged that they need to restart their universe, through an apocalypse of at ''least'' Class X-4 to fix it. And best of all? The restarted time line is the one Jake comes from.
GC: "L1ST3N TH3 UN1V3RS3 W1LL 34T P4R4DOX3S FOR BR34KF4ST... G3T US3D TO 1T"
The Green Sun, born of the destruction of two universes. Yet the power of the Green Sun is what destroyed them.
To clarify: Doc Scratch, a being powered by the Green Sun, set forth a plan that would end in Earth and Alternia being destroyed. Earth was destroyed by the Sovereign Slayer, another being powered by the Green Sun, while Doc Scratch personally manipulated events on Alternia to lead to the destruction of the universe. The circumstantially simultaneous destructions activated the Tumor, a giant bomb that, when activated, will create the Green Sun. Ironically, the people who put the Tumor in place thought they were trying to destroy the sun...
On top of all this, the Green Sun is located at the center of the Furthest Ring, where distance and time interact in incomprehensible ways, so that you have to know the proper route to not only ensure you end up where you're going, but you get there at the right time too; going three feet to your left could rocket you a million years into the future, and you'd never even notice until you got there.
Not to mention the fact that their attempt to destroy the Green Sun, due to the nature of the Furthest Ring, ended up making them travel back in time to create it, thereby setting in motion the events that would lead to them trying to destroy it (in other words, the events of the entire comic).
A more minor example, which still emphasises the nature of Weird Time Shit, is when Present-Karkat is on his bulletin board, having an argument with Future-Karkat. Eventually Future-Karkat logs off, having left Present-Karkat in precisely the right state of mind not to take any crap from Past-Karkat when he logs in. (Not only that, but Present-Karkat changes his typing colour from grey to candy-red to make a point because Future-Karkat is "already" doing it.)
and honestly, that kind of stuff happens pretty much every time Karkat uses the bulletin board system, this just happens to be pretty much the least confusing example.
The big bad of the series has similar powers. He uses stable time loops to ensure his own existence.
Jujus, special magical items, are so rare that only one can exist anywhere in the multiverse at any one time. It turns out that all jujus we have seen in the series are ontological paradoxes, they are passed from one person to the next, and due to time travel come into the possession of the original owner.
A major one in Two Evil Scientists occurs when Tails attempts to bring Sonic and Mega Man back from the time periods Quint sent them to, only to accidentally rescue the titular scientists from their former self-destructing fortress, after which they suddenly became dangerous — which was the primary reason Tails was trying to bring Sonic and Mega Man back.
Shelly of Wapsi Square managed to take advantage of time loops and places where time flows in different directions to arrange the Vision Quest gone wrong in her childhood that had a huge influence on her character.
Lampshaded in The Omega Key when the characters discover that they themselves, via time travel, were responsible for the destruction that they thought they were wrongly accused of.
This probably happens in this strip. The time window that Bang sees the first time happens after the second one from the point of view of the characters in the window. Gil calls Bang a maniac in the first one, probably because she pointed a gun on them in the second one, which she did because "earlier" he insulted her.
In the sidestory ''The homecoming king" (from here to here) some students summon the Ht'rok'dyn (the first Heterodyne) from the past. He learns that he has descendants who created a big empire, so he goes back in time to make sure it happens.
Faulty Logic: Fox travels to the future to steal a comic idea from his future self. When he gets back, his past self snatches the page out of hand and disappears.
The 2011 time travel Story Arc in The Packrat explains why Buchla modular synthesizers have no keyboard: Packrat scared and angered Don Buchla and destroyed his synth prototype with his time machine keytar.
Schlock Mercenary: Defied. When dealing with an exploding galactic core, a missile with exactly the same ID signature as one which already exists is detected. It turns out it came from the future, which gives Kevyn the idea and means to travel back in time and prevent the problem from ever occurring, and also save Tagon's life. However, rather than first send the missile back to give him the idea, Kevyn destroys the present version of the missile to prove that the universe does not enforce one. After all, if it did, there would be no point in what he's about to try.
Later, Alternate Future!Kevyn pretends to build a machine which can send messages through time, claiming they follow this trope. It's just a fake to buy time to be rescued.
Sonichu did this once. Author Avatar Chris and his companions return to the point where Chris would get smacked with a basketball in high school and be inspired to create "Bionic". However, it turns out that the ball was actually one of the Sonichu-whatever-it-is-being-called-at-this-point and, to make sure it ended up this way, Chris swaps the two.
This is essentially one of Dr. Insano's backstories as part of The Spoony Experiment: Insano is an alternate-universe version of Spoony, who has grown so angry with the Final Fantasy franchise that he wants to go back in time to erase it from existence. Since being able to travel through time would require him to study science for decades, he decides to create a time loop just like that of the originalFinal Fantasy by studying science, travelling back in time and then obtaining all the knowledge he needs from his future self.
In Red vs. Blue, Church creates an uncountable number of these as he fails his objective each time and keeps trying.
Local Cloud Cuckoolander Caboose makes the following unintentionally profound statement when Church talks to him about his experiences with the timeline: "Time LINE...? Ehh, time isn't made out of LINES. It is made out of circles. That is why clocks are round!"
In Illo Tempore contains at least two stable time loops across four millennia.
The Flash game No Time To Explain. Your character is chilling at home when a future version of himself appears out of thin air, warning you of imminent danger. Seconds later, a giant crab grabs him and carries him away, leaving you to use his weapon to save your future self. After defeating the crab, your future self opens a time portal back to the beginning of the game before dying. You travel back to your past self's living room, and try to warn him of the danger your future self warned you about. Seconds later...
Robutt a robot is trapped in a time loop wherein it constructs itself out of junk, sacrifices its battery to power the new version, which gets in a time machine and goes back to do it again.
In We Are Our Avatars, Komatsu and the others teach a few of their moves to a younger Toriko, setting Toriko's path in becoming a great Gourmet Hunter. In fact, Toriko learned his Knife and Fork techniques from Grey Fullblaster.
In Chronicle of the Annoying Quest, when the party reaches the Caverns of Time, Guy accidentally activates a rune that displaces him in time from previous points in the story, including his original warlock apprentice outfit, his tier 1 set ghost form, and his tier 2 set undead form. After a few confused remarks by the past versions, Guy casts a spell to send them all back. What makes it an example is present!Guy's reaction to the situation:
"Oh, so this is when all that happened! I thought it was just a recurring dream."
Starwalker: Starwalker's drive allows her to travel through time. This gets the attention of some Space Pirates who take over the ship. They force her to use her drive to go to the Solar System. Using the ability to travel in time, Starwalker gets them to the appointment 40 years early. They return to the present. However, the ripples of their passage causes strange measurements to be made of our sun. This gives Dr Cirilli the idea that a star step drive could work. In the "present" they meet the person who hired the pirates. She turns out to be the avatar for our sun. She hired the pirates to end the Starwalker experiment because the star step drive has the side effect of Star Killing.
random_nerd: Completely ridiculous, I say! Everyone knows the Titanic sank from the added weight of all the time travelers trying to stop it from sinking.
In Duck Dodgers, the queen of Mars finds out the one moment in his life that inspired Dodgers to become the person (or duck) he is, and sends Marvin the Martian back to prevent it. When he arrives, though, he finds that Dodgers was just a waterboy then. Refusing to believe that they were wrong, Marvin tries to make it happen the way it did, and fails his mission to stop it in the process.
In Futurama's episode "Roswell That Ends Well," Farnsworth is very adamant about not changing the past, unless of course it turns out they were supposed to change the past, in which case, they must, for the love of God, not not change it. Fry ends up killing his grandfather Enos by mistake, after an attempt to keep him safe. He impregnates his grandmother, thus becoming his own grandfather, which becomes Chekhov's Gun. After that, Farnsworth gives up about not changing the past. The crew blasts up Roswell Air Force Base, steals some gear, rescues Zoidberg and Bender's body, and blasts off into space. Farnsworth then delivers one of the best lines ever: "Choke on that, causality!" Oh yeah, and throughout all this, the crew ends up being the mysterious alien ship that crashed in Roswell, and Zoidberg is the alien.
Later, the aforementioned Chekhov's Gun comes into play, which gave him a birth defect that enabled him to fight the Brainspawn. He ends up trapping himself with the Brainspawn, and they send him back in time, so he can avoid falling into the cryogenic tube, and live out his life in the 2000s. It turns out Nibbler is the reason he fell (Nibbler never went back in time, he's just that old). Nibbler convinces him to stay by saying he might have a chance with Leela in the future, and thusly helps himself fall alongside Nibbler. In a clever twist, on an earlier flashback episode, you can see Fry and Nibbler's shadows just as Fry falls into the tube.
If you look carefully at the pilot episode when Fry puts down I.C. Wiener's pizza on the cryogenic lab desk, you can see Nibbler's eye poking from under the desk. Yes, the writers planned that far ahead.
Bender's Big Score adds a few more. The aliens that destroyed civilization in the background while Fry was frozen? That was Bender gone back in time. Fry's dog turned out to have a happy life with a copy of Fry who chose to stay behind in the 2000s, while letting his other copy freeze to the year 3000. The dog gets killed and instantly fossilized when a mind controlled Bender blasts Fry's apartment. Lars was the copy of Fry who decided to stay in the 2000s. He makes it to the year 2012, making him biologically older than the Fry we know, and his larynx and hair were damaged in the blast. He remembers the name Lars from the future, and thusly knows what to name himself and how to act. The Bender tattoo that allowed him to travel back in time in the first place is glued on by a repaired Bender who did just that in a seemingly random part in the middle of the movie, but who got it from Lars/Fry's dead body at the end.
Also, in the movie, their main method of time travel is stated to be a self correcting method. Thusly, any copies made using the time travel are doomed to die horribly at some point. Some last longer than others. Farnsworth and Nibbler state that there can't be any paradoxes, and if there are, such as by the end of the movie where it's revealed there's hundreds of Benders (all of whom one Bender foolishly tells to stay underground until that moment, thus completely screwing up the timeline of the whole movie and creating hundreds of paradoxes), it rips open a hole in the universe, which is exactly what happens, leading to the events of the second movie.
The Game actually had the entire plot, which was a giant Shoot the Shaggy Dog story about trying to prevent Mom from conquering the world by buying Planet Express, and dying while failing to do anything other than set up a seemingly random joke at the start.
In an episode of Mary Shelley's FrankenholeThe Wolfman 1941 is bitten by a seemingly unknown werewolf and his girlfriend tries in vain to kill him with regular bullets before shooting herself. Decades later (after Dr. Frankenstein tries in vain to stop his immortality as a werewolf), he travels through a Frankenhole portal to the past and attempts to give his beloved a silver bullet loaded gun... before turning into the werewolf that bit him in the first place. Plus, the gun he tried to give her is the same one that she ended up killing herself with.
Time travel (via the Phoenix Gate) can't be used to change the past — no matter what you do, You Already Changed The Past. But if the plot requires it, you can turn yourself into a god by means of a Stable Time Loop. The Avalon arc includes the flashback antagonist known as the Archmage in a classic bootstrap scenario: he travels back in time, saves himself from his canonical death at the bottom of a cliff, spends a day jumping through time handing his past self an absurd amount of firepower, ending the day by sending his past self off to repeat the process.
Magnificent Bastard David Xanatos uses this to his advantage in "Vows". When pulled to 975 AD, he gives the Illuminati a coin to hold onto for one thousand years, and then deliver it to a young David Xanatos. The coin wasn't worth much in the past, but by the time it reaches him in 1975, it's worth twenty grand, which is the foundation for his fortune. He also gave them a letter to hold onto for 1,020 years, so he'd get it precisely one week before the episode began, telling himself exactly what to do. He makes a direct Lampshade Hanging of the trope when Goliath arrives to rescue him.
Goliath: If I didn't fear the damage you'd do to the timestream, I'd leave you here. Xanatos: But you won't. Because you didn't. Time travel's funny that way.
Goliath found out that history is immutable to his dismay in the same episode. He tried to convince teen Demona not to turn evil. It worked, but only temporarily.
In the same scenes, Demona always knew history is immutable because she already saw it. Future/Present Demona was the one that brought them all to the past in that episode, and then she goes to her younger self. She travels 20 years into the then-future, to 995 AD, and Goliath catches a ride. She shows herself the slaughter of Wyvern castle, that all her rookery mates are dead, and then tells herself to get rid of all the humans. Initially her past self rejects this, and she fights herself. She at first seems to reject what her future self told her, and embrace what future Goliath told her as she is returned to 975. However, by the time those twenty years pass, she makes a plan to do exactly what her future self told her to do, eliminate all the humans from the castle. This causes the scene her future self used to scare her in the first place, resulting in the classic irony this trope generally causes. Future Demona wasn't actually trying to change it though, as she remembered what happened to her past self that night, and knew what would happen, it was all a trick to turn herself evil and turn her into the person she becomes.
The final irony of this is that young Demona was simply told "the humans" destroyed our clan. She assumed it meant the humans in the castle, and tried to get rid of them by allowing the Vikings to sack the castle. In reality, it was the Vikings who killed the gargoyles, so this became a classic case of fulfilling a prophecy by trying to stop it.
The self-correcting timeline variation shows up in an episode when Goliath saves a World War II pilot from dying. Seemingly random accidents keep almost killing him until Goliath brings him forward into the present, fulfilling history's decree that the pilot no longer lives in that time.
The episode "M.I.A." hints at what could be a possible out within one: Goliath travels back to World War II London to investigate an accusation that he caused the death of a gargoyle back then. When it seems that the Gargoyle in question really is marked for death by fate, Goliath takes him to the present day with him, saving his life, but still preserving the effects of his death. Or fate could just have been screwing with him to achieve the predestined result.
The Star Trek: The Animated Series episode "Yesteryear" has Kirk and Spock return from a trip to the past to find that the ship suddenly has a different science officer, and no one else knows who Spock is. Spock relates a memory from his childhood when his life was saved by an adult Vulcan, who he realizes looked exactly like he does now. So he has to take one more trip to the past to save himself and set things right.
In a very odd scene, the alternate-history science officer, an Andorian, is informed by Spock that Spock's plan, if successful, will mean the Andorian will no longer be the science officer for the Enterprise — and may in fact cease to exist entirely. The Andorian accepts this notion with an almost eerie calm, and wishes Spock the best of luck on his quest.
Mojo Jojo goes back in time to try to kill Professor Utonium as a young boy to prevent him from creating the Powerpuff Girls. The girls follow and save The Professor, and it was this very incident that inspired him to get into science and try to create "the perfect little girl."
In another episode where Mojo captures the Professor, it's revealed that Mojo's continued existence is proof that this plan was Doomed by Canon because the blast that the girls made on being born mutated a lab monkey into Mojo himself.
The Fairly OddParents full-episode special "The Secret Origin of Denzel Crocker": Timmy goes back in time to figure out why Crocker is so miserable. He discovers that Crocker had fairy godparents as a kid, and not just any random fairies, either—Cosmo and Wanda were his fairies. Since present-day Cosmo and Wanda had no memory of this, they quickly figure that Crocker had done something to lose his fairies. They then set out to try to stop this, but Timmy ends up being the one revealing Crocker's secret in public. Worse still, he leaves A.J.'s "Crocker-tracker" in the past, which Crocker managed to reconfigure with Cosmo's DNA, making it a much more effective "Fairy-Finder" than the one present-day Crocker previously had.
...which actually proves to be only a semi-stable time loop. If it were a true stable time loop, Crocker would have had AJ's tracker the entire time. Either that, or he 'forgot' that he had it until immediately after Timmy gets back from his time-travel.
This loop actually has a logical beginning. Cosmo is about to reveal Crocker's secret to a large crowd, but then Timmy stops him, only to reveal the secret himself. Less of a time loop, more of Timmy kicking the can a few seconds forward and becoming the cause himself.
And the reason Cosmo and Wanda didn't remember having Crocker as a godchild? The past Cosmo was playing with the device Jorgen Von Strangle used to erase young Crocker's memories of having fairies (the device being a reference to Men In Black) and accidentally erased his and Wanda's memories of having Crocker as godchild.
The Transformers featured a truly epic multi-layer time loop revealed over the course of several episodes. 11 million years ago, A3 led a revolt against the Quintessons; however, in 2006, the Quintessons yanked A3 into their own time to prevent themselves from losing Cybertron. Blaster, Perceptor, Blurr, and Wreck-Gar go back in time to help the rebellion, while the Aerialbots save A3 from the Quintessons. A3 returns to his own time to lead the rebellion. Two million years later, A3, now known as Alpha Trion, meets the Aerialbots, who have travelled back in time from 1986. The Aerialbots persuade him to save the life of a young dock worker named Orion Pax, who he rebuilds into Optimus Prime (and also rebuilds Orion's girlfriend Ariel into Elita One). The Aerialbots return to their own time and then, in 1984, Optimus Prime and Alpha Trion build the Aerialbots from a group of shuttles. You may wish to draw a diagram.
In the Pinky and the Brain episode "Brain of the Future," the two mice travel to the distant future in a time machine given to them by their future selves, who had just returned from the distant future. There, they lose the time machine they arrived in but manage to steal a "different" one and return to give it to their past selves...
Kim Possible: A Sitch in Time has this. Shego stole the time monkey only because she stole it, went back in time, transferred Ron away from Kim, and then told herself to steal the time monkey. This somewhat changes when the time monkey is destroyed and the entire timeline that its use created is revoked, along with the very existence of the time monkey. So, you destroy it once, it erases itself from ever existing. So Shego never went back in time, Ron never left KP, and nobody ever knew or cared about the time monkey.
And within that wheel, Shego takes the monkey while in the past and escapes into the timestream, so Kim goes straight from the past to face Shego in the Bad Future. Shego manages to Take Over the World partly because Kim wasn't around to stop her, since she skipped over that whole time.
The movie "Ego Trip" starts with robots appearing in the lab, looking for "the one who saved the future" and Dexter assumes they came to kill him. Inspired by this, Dexter hops in his time machine and ends up going on an adventure with three future versions of himself, battling four Mandarks. In the end, the day is saved when Dee Dee walks in and does her thing. Furious at being upstaged, the four Dexters build some robots and send them to beat up "the one who saved the future". When he realizes this, Dexter's reaction is to give up on explaining time travel and then going to eat lunch.
The first episode had Dexter and Dee Dee attacked by a giant blob monster from a wormhole. Dexter gives Dee Dee a message warning him about the monster. She then uses it as an opportunity to blackmail an originally reluctant past iteration of Dexter (who is wrapped up in working on an invention). This annoys Dexter to the point where he tries to send Dee Dee into an untested wormhole that spews the monster. Dexter then repeats the previous events and tries to give Dee Dee the message, but Dee Dee then finally gives him the message he had wanted all along, thus sealing his fate. It is also revealed that the invention Dexter was working on was that very wormhole that sealed his fate.
A time travel episode in SpongeBob SquarePants had Squidward going to the distant past through a series of events stemming from avoiding Spongebob and Patrick trying to get him to go jellyfishing with them. He meets the caveman versions of them and shows them not to be afraid of jellyfish by demonstrating jellyfishing, then giving both nets to try it themselves. Upon his return, he mocks whoever was the one who invented jellyfishing, to which Spongebob and Patrick tell Squidward it was him.
The intro short for The Simpsons theme park ride has this. Professor Frink learns that Doc Brown's Future Technology Institute was bought out by Krusty the Klown and closed down, and uses the DeLorean to go back in time and prevent this. When he arrives, Frink accidentally runs down the investor to whom Doc was speaking, forcing him to sell the Institute to "that mercenary clown".
Teenage Mutant Ninja Turtles (2003), notably in "Timing is Everything," in which the events of this episode are heavily implied to be the reason why the Shredder became so ruthless in his hunt for the turtles during the "The Shredder Strikes Back" two-parter. The Shredder that appeared in "Timing Is Everything" was right after the events of "The Shredder Strikes, Part Two" (as in, right after he broke out of the wreckage of the water tower that fell on him), and learned of his eventual defeat at their hands. Thus, he resolved to ensure it never happened, resulting in the events of the follow three or so seasons — making his defeat inevitable.
Raphael: "We put the kabosh on you a long time ago! You're history!"
In Teen Titans the time-travelling villain Warp thinks he's taking part in one; he goes back in time to steal a special clock because, a hundred years in the future, the historical records say that he went back in time to steal it. Unfortunately for him, the Teen Titans prove themselves able to Screw Destiny and stop Warp from stealing the clock, wrecking the time loop.
An episode of Family Guy explicitly pointed out the trope when Stewie and Brian accidentally caused the Big Bang due to time travel.
In the My Little Pony: Friendship Is Magic episode "It's About Time", Twilight Sparkle comes across her (lightly injured) future self, who came from next Tuesday morning to give her a very serious message, but Twilight keeps interrupting her future self, until she gets sent back to the future before she could finish her warning. Present Twilight spends the next several days worrying about averting impending doom and getting more and more injured because of random events, matching up her future self's injuries until next Tuesday morning comes, and absolutely nothing bad happens, which is when Twilight decides to use a special magic scroll to go back in time and warn her past self that nothing bad was going to happen and she had no reason at all to worry about. Unfortunately, her past self kept interrupting her until the time travel spell wears out and Twilight returns to the future- which is now her present. Then she realizes what she has done: her half-done attempt to warn her past self about not worrying is what made her worry in the first place and created a stable time loop. After a few moments, she decides to shrug it off and declares it her past self's problem now.
To add to this, Future Twilight tells her past self where to find the time spell.
Gravity Falls episode "The Time Traveler's Pig" combines this with Self Fulfilling Prophecy and You Already Changed The Past. Time traveler Blendin Blandin comes to the present from the year Twenty-Snevety-Twelve to prevent series of time-anomalies from occurring. It turns out that the anomalies were caused by Dipper and Mabel messing around with Blendin's time traveling device, dropping several items around past episodes, and Blendin is sent to retrieve the litter- explaining why Blendin popped up in those episodes as a Freeze-Frame Bonus.
In Regular Show episode "Prank Callers", while being chased by the Master Prank Caller in the 80s, the gang ended up accidentally running over Pops, turning him into the ditz he is in the present.
It gets weirder since Pops was the one who gave Mordecai and Rigby the 80's cell phones that brought them back in time, and Pops gave them the phones while he was falling for a prank call Mordecai and Rigby pulled on him. (They asked him to wait for a collect call from Joe Momma. And he did.)
In Adventure Time episode "Betty", Simon created a portal to the past so that he can say goodbye to Betty and to gain her forgiveness. This is because he believed she left him after putting on the crown that led him to become the Ice King. She then jumps on the portal, explaining her disappearance as years go by.
In the Uncle Grandpa episode "Future Pizza", Future!Uncle Grandpa goes back in time to warn Pizza Steve that he will lose all respect for him for reasons he can't explain. Pizza Steve then spends the entire episode worrying about everything he does being the thing that makes Uncle Grandpa lose respect for him, and near the end, he tells Uncle Grandpa that he's giving up on doing awesome stuff altogether. Uncle Grandpa tells him that all the awesome stuff he does is what makes UG respect him, which causes him to believe that giving up was what made Uncle Grandpa lose all respect for him. He then does everything he had wanted to do before, and asks "I didn't disappoint you, did I?". It then turns out that asking if he was disappointed was what made Uncle Grandpa lose all respect for him in the first place, and Uncle Grandpa goes back in time to warn Pizza Steve not to do that.
You never thought you'd see it, but some non-trivial physicists are wonderingaloud whether the future is actively trying to scuttle the LHC research project. The string of mechanical difficulties, they say, may be more than mere chance: Whether through [future] human intervention or the universe itself exercising some form of upstream-acting Ontological Inertia, the future is trying to make sure we don't mess with Higgs Bosons. Loopy? Literally. Crazy? Probably. Impossible? Well...
In terms of the theory of relativity, time travel would take the appearance of a closed timelike curve, which is a series of events returning to its starting point — such as time travel returns to the past. That leads to the inevitable paradoxes, but some solutions claim that if time travel is possible at all, it's only possible in a stable form: the only form of time travel possible generates one.
While that may seem supremely useless — what good is a time machine if it can't change anything? — that's not really true. A computer that could only build Stable Time Loops could run algorithms like "open time communication channel to 5 minutes into the future, receive answer from future, close channel, check answer (which takes 5 minutes in this example), if correct, send answer over the communication channel that was now just opened, if incorrect send different answer to past over the same communication channel", and then consistency would force the algorithm to return the output to some given puzzle. This is known as Time Loop Logic. Receiving an incorrect answer from the future would cause a paradox, and thus is impossible. Therefore either the answer will never arrive, or you will have created an ontological paradox, fabricating the answer from nowhere. The step of checking the answer is required for the algorithm to work.
Less esoterically/more science-fictionally, a time machine that can't change anything would also be just dandy for observation, thanks. (Better, really, since you don't risk stepping on the Butterfly of Doom.) Video from 20,000BC anyone?
Some theories of particle physics hold that antiparticles (particles with the opposite charge and parity of a "standard" particle) travel backward through time. It's also widely believed that particle-antiparticle pairs randomly pop into existence from the Quantum Foam, and then feel their mutual attraction and annihilate each other moments later. It's also possible to see this as a single particle traveling in a loop through time: Forward as a regular particle to annihilate with its antiparticle, then backward as its antiparticle to annihilate with its standard particle, and repeat.
A few theories state that, assuming time travel is possible, the big bang could have occurred by sending a time machine back to the starting point of the big bang, which would be a void before 'existence'. The sudden appearance of matter would then trigger the big bang, causing us to exist and said time machine to be constructed.
There is another theory that says that if time travel is possible, it is only forward time travel — theoretically caused by time dilation when approaching the speed of light. The other way says that time machines are possible but that you can only travel to when the time machine was first activated and any time after that, but not before. That would explain why they aren't hundreds of time travelers at every major event in history... yet.