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Ripple-Effect-Proof Memory
"But one night, me and John got really drunk and we sat around telling Todd Brinkmeyer stories, real stories, stories that happened but didn't happen. I think of his face and sometimes I can see it, and it's like a dream you can't quite remember the next morning. And I go back and go over the chain of events and there's places, holes where I know Todd should be."

When Time Travel is used to "rewrite" past events, this character will retain their memory of the original timeline—i.e., how everything went the "first time around"—even though that version of events no longer will have happened. Everyone else will only remember the new reality. This is a Necessary Weasel for time travel stories; how can they Set Right What Once Went Wrong if they don't know something went wrong?

This could be justified a number of ways: it doesn't affect time-travelers, the character used Applied Phlebotinum, they are Immune to Fate, they are a Time Master, etc. The bottom line is that this character has an advantage that no one else does and this is why their memories are unaffected by someone rewriting time. Expect the Timey-Wimey Ball to be thrown around to explain stuff like this. If You Already Changed The Past is involved then the explanation is much simpler; they knew it would happen because they already did it.

The trope becomes trickier when characters who don't have the above justification get Ripple Effect Proof Memory anyway. A Psychic Nosebleed might ensue when someone whose memory isn't completely "proof" gets an "update" on a new lifetime and the mental stress from trying to contain memories from a large number of timelines actually harms the physical body. This might happen even if memories are the only thing that carry over from shift to shift and the time traveler is no longer in his or her original body. The technical term for this is "the time travel clone memory feedback problem." We're working hard to find a cure.

Ripple Effect Proof Memory is inherent in any and all "Groundhog Day" Loop, Mental Time Travel, and It's a Wonderful Plot. As we already have pages on them, instances of them shouldn't be included here. Individuals with a Ripple Effect Proof Memory may be the only ones who recognize a Ripple Effect Indicator for what it is. When Played for Drama, if this is a rare ability then a character with this may feel isolated and lonely, being the only ones who remember the "original" timeline.

The name refers to the "ripple effect" from the Back to the Future films.

Examples

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    Anime & Manga 
  • In The Disappearance of Suzumiya Haruhi, when Yuki reshapes the world, Kyon is the only one who remembers, because Yuki wants him to have a Reset Button.
  • Occurs in Xxx Holic and its sister series Tsubasa Reservoir Chronicle several times due to some major futzing with the time-space continuum, but the most obvious example is Yuuko who is Ret Goned from the memories of every except close friends and relations once her time starts moving again and the universe is rewritten to be as it would have been had she died when she was supposed to. Interestingly, despite being one of the few people who do remember, Watanuki is still terrified he'll one day lose his memories too, which is part of why he goes through such a drastic personality change after her death.
  • Deconstructed in Mazinger Z spin-off Shin Mazinger Zero. Kouji and former Fem Bot turned into Robot Girl Minerva-X are locked into a Groundhog Peggy Sue loop. Both of them have this. However Kouji's memory is faulty, and he only remembers what happened in former timelines through dreams and sudden flashbacks, and they are so vague and so random -and seldom he has them when he needs them- that they are all but useless. On the other hand, Minerva remembers with utter clarity how they failed thousands of times in averting The End of the World as We Know It, and how her beloved, her friends and the whole humanity died several thousands of times because she failed.
  • All instances of Time Travel in Pokémon. In Arceus and the Jewel of Life, Ash & co. remember events as they happen after Dialga sends them back through time, but they also remember the original history that necessitated the trip to start with. Arceus itself is subject to Delayed Ripple Effect, and nearly blasts them before its memories catch up.
    • In the Japanese version of the Celebi movie no one remembered as well. The dubbers felt that it too closely mirrored the first movie which ends with Mewtwo erasing the movie's events from everyone's memory, and elected to change it. They discuss the matter, and an additional scene with Professor Oak reflecting, in the commentary.
    • In the season 9 (Battle Frontier) episode "Time Warp Heals All Wounds" May, her Squirtle, and Meowth travel back in time to save a man's life and end up saving his hometown's economy in the process. They're the only ones who remember the ramshackle version of the town from before their time trip.
  • In Serial Experiments Lain episode 11, Lain's child-like incarnation (I think) alters history to remove some rumors around school about Arisu but leaves Arisu's memory intact. After all, memory is just data. Arisu finds the whole experience a bit unnerving.
  • In Episode 117 of Yu-Gi-Oh! 5Ds, it is revealed that Yliaster were able to alter history. When they did so, only the Three Emperors, the Signers and those within their protective fields, and Team Ragnarok (who held the Polar God Cards), were seen to be aware of the changes.
  • In the CLANNAD anime adaption, both Nagisa and Tomoya retain the memories of the first timeline when Ushio hits the Reset Button.
  • Puella Magi Madoka Magica,
    • Homura remembers all the different timelines because she is a Time Master. Every time she returned to the beginning of the "Groundhog Day" Loop, she was the only character who could remember what happened the last time, though Madoka was Dreaming of Times Gone By.
    • At the end of the series, no one remembers Madoka save her little brother Tatsuya and her very best friend because her wish made her Ascend to a Higher Plane of Existence. Since she's now a transcendent law of the universe, she remembers everything that was, that will be, and that which can't possibly exist. In the case of Tatsuya, Word of God states that since he's a toddler, he's too young and innocent to understand why Madoka should not exist and therefore will come to forget her once he grows up.
  • Okarin from Steins;Gate has one of these. John Titor wants him to use it to become the Messiah and overthrow the coming new world order. He calls it “Reading Steiner” which doesn't really mean anything but sounds pretty cool.
    • Played more plausible than most examples since he usually gains no more than a weeks worth of memory at a time and it still disorients him immensely to the point of Idiot Ball (from the point of view of other characters who don't have this ability).
    • Also, not only is Okabe the only person with this effect, but he has no idea how he got it or why, though it's implied it was due to a childhood illness. Many of his problems from the first half of the series are caused by not being able/willing to see the world changed, which coupled with the social skills of a turnip results in him scaring or temporarily vilifying most of the main cast. Then the Knight of Cerebus shows up ...
    • The Movie explains this more and thoroughly deconstructs it. Turns out all humans have his ability, it's just far, far weaker. It's called "déjà vu." And Okabe's ability to recall different timelines slowly starts to become a case of Blessed with Suck as the knowledge of so many alternate worlds is beginning to cause some mental breakdowns...
  • Averted in Doraemon; everyone, not just Nobita and Doraemon who has any relation to the Time Travel will remember the events, although this rarely happened or even mentioned. The most notable and recurring example is Nobita's grandmother who remembered everything about Nobita's multiple visits to the past.
  • While not necessarily related to Time Travel, anyone with knowledge of the Crimson World in Shakugan no Shana can remember the existences of people or things that have lost their Power of Existence.
  • In Fairy Tail, after the Grand Magic Games draw to a close and the dragons are brought back from 400 years in the past through the Eclipse, the heroes start dropping like flies while trying to fight them. Seeing this, Ultear pulls a Heroic Sacrifice by casting a spell that turns back time at the cost of the rest of her own time. It turns out this is only enough to rewind time by one minute... But it also turns out that everyone in the world is able to remember that one minute, which allows the ill-fated heroes to dodge their own deaths and predict their enemies' movements, effectively turning the tide of battle.
  • Hatou from Murasakiiro No Qualia can share memories, experience and knowledge with her selves from parallel worlds.
  • In the Haiyore! Nyarko-san light novels, Ordinary High-School Student Mahiro Yasaka has the extremely rare ability to perceive and be unaffected by shifts in the space-time continuum. This gets an off-hand mention in one of the first novels, but comes back in a big way later, when Nyarko and Cuuko get Ret Gone by a bitter ex-classmate, and only Mahiro knows anything's changed, meaning he's the one who has to save the day. Considering how much author Manta Aisora loves referencing Kamen Rider, this may well be a Shout-Out to Kamen Rider Den-O and its Singularity Points (see below).

    Card Games 
  • In Chrononauts, certain Identities have Ripple Effect Proof Memory, but they come from different timelines. These players win by restoring history to however they remember it. Others try to change history from our (and their) history to one which they prefer — such as Betty, who wins by saving JFK in 1963, and Yuri, who tries to make the USSR win the Cold War.

    Comics 
  • This was in The Authority, when The Doctor (not that one) has to relinquish his powers to one of his predecessors (one who was stripped of them for being a depraved omnicidal maniac). The old Doctor stops in the middle of the fight to point out that he can freely travel through time, threatening them with "imagine fighting someone who could shoot you as you emerged from your mother's womb or hold a pillow over your face in a retirement home." He then adds "worse still, imagine the local doctor, back when you were in high school, giving you a funny feeling you'd carry around for the rest of your natural life". He doesn't go as far as raping The Engineer (or if he does it's off-page, or has been changed in the reprinting) but the comic does take a panel to show him kissing her on the back of the neck. He asks her "Hello again, Miss Angela Spica of class 4B. Remember me?" which starts her crying and whispering "oh my god..."
  • During Crisis on Infinite Earths, after all the various Earths merge into one coherent history, all the superheroes who survived the transformation wake up the next day with their memories intact, though these fade in a few months, replaced with ones where they lived in the shared universe all their lives and had memories of fighting in a battle against the Anti-Monitor in 1985. The only person who actually remembers the Crisis and the infinite universes that preceded it is the Psycho-Pirate, who at the end of the series is shown to reside in an psychiatric hospital, rambling about the events of the Crisis, while everyone thinks he's mad. Later on, Psycho-Pirate's ripple-proof memory becomes a major plot point in Grant Morrison's Animal Man, when he gains reality-warping powers and tries to bring back all the characters lost in the Crisis, as he's the only one who still remembers them.
  • In the Marvel Universe, Bishop has occasionally ended up like this, due to doing a bit more time-travel than is really healthy… After the Age of Apocalypse timeline was destroyed, and everything went back to normal, he experienced some occasional 'regression' into memories of the now-defunct timeline — up to and including attacking Beast and Cyclops, who were evil in the other universe.
  • Likewise, explained within the Astro City series, as anyone jumping into the 'empyrean fire' of the time stream seems to be immune to the effects of any temporal changes. That such a thing also happens to impart the user with superpowers and would be the only way to make the local pastiche of Superman/Captain Marvel/generic hero work without a paradox is just an extra bonus. Oddly, some people in the series have at least some resistance to the Ripple Effect. A viewpoint character Michael Tenicek has his wife erased from reality by an unsuccessful attempt by a villain to muck with the timestream, presented in the style of a Crisis-like event. He remembers the old timeline only when he dreams. He is given the choice to forget, but declines the offer... and is informed that no one ever does.
  • In the Marvel mega-crossover event House of M, Wolverine and a new character called Layla are able to remember the original timeline, how things were before the Scarlet Witch rewrote history. Layla is a mutant with this (and the ability to undo time travel's effects on the memories of others) as her stated superpower. Strangely enough, Spider-Man gets the feeling that things aren't quite right with the world and writes a journal detailing the events of the original timeline, but no reason is given for that. When the Scarlet Witch changes everything back, Spider-Man still remembers the House of M reality and nearly kills Quicksilver, furious about what he remembered having "lost" (a world where Uncle Ben never died, and Peter had started a family with Gwen Stacy).
  • The Flash
    • Bart Allen, the hero known as Impulse, Kid Flash II and (briefly) Flash IV, has a permanent version as a result of being sent from the future. On the more notable occasions Wally West's wife was removed from time, the entire Flash lineage was erased and scary future versions of the Titans went back and changed the future they came from, and he was entirely unaffected. Bart wakes up in the 30th Century during Flashpoint and is still fully aware. However, being stuck 1000 years in the future leaves him almost completely unable to help with the main story. Naturally he is killed off at the end of his miniseries, presumably so that no one will be able to remember the old timeline once the New 52 came around…
    • Played with in Flashpoint where Barry Allen wakes up one day to find the world is completely different, and the least of the changes is that he never gained superpowers. He's the only one who remembers the previous timeline, but this memory is slowly being erased and replaced with memories of the new one. Thus it takes Barry almost the entire series to realize that he's the one who changed the past in the first place, by going back and preventing his mother's murder. Also completely averted with the ending, in which the timeline is changed again (to one very similar to the "correct" timeline, but with some differences.) This time, no one remembers the old timeline, including Barry.
  • Tom Strong featured an aversion of this trope. His greatest adversary managed, at one point, to take over the time stream, and used some new technology to open a time gate, pulling versions of himself from all points in his life through the gate and into the timeline. He ended up with the backflow of over three hundred separate memory streams converging on his head all at once- luckily, the Clock Roach guardian he defeated to take over the time stream felt generous enough to send them all back, with the note that the youngest of them will have to go through every single one of the summonings and unsummonings. The mental chaos this event produces drives the villain to madness and probably leads to his downfall.
  • In the infamous One More Day, Spider-Man makes a deal with Mephisto in order to save Aunt May's life, which rewrites decades of Marvel continuity to create an alternate timeline where he was never married to Mary Jane. It's even a plot point in certain issues, where characters that knew Spidey's identity beforehand (such as the Fantastic Four) have forgotten, and only by showing his face will their memories be restored. The only people who remember Spidey's identity from the beginning are Mary Jane and his clone Kaine, Deadpool is also hinted to remember because he demolished the fourth wall long ago, but he's never yet used it beyond a Take That.
  • In Archie Comics' Sonic the Hedgehog, this comes up during the Mobius: X Years Later stories. After the timeline gets altered, some handy Applied Phlebotinum allows Sonic and several of the other heroes to remember the unaltered reality. The same Applied Phlebotinum also allows Lien-Da to remember as well, while King Shadow is able to remember simply because of his Chaos powers, which are themselves a loose form of Reality Warping. This seems to be the effect in the post-Sonic the Hedgehog/Mega Man: Worlds Collide Mobius and beyond: some characters, like Sonic and Blaze, remember the original Mobius, while others, like Amy Rose, Cream the Rabbit and Naugus, are haunted by memories of the previous universe or don't remember it at all. This is because Eggman screwed up Sonic's Chaos Control in a last-ditch attempt to claim victory.
  • Done in Paperinik New Adventures where, after a time rewrite, a select few get occasional flash-backs to how reality was supposed to be. Odin Eidilon then checks his own memory against a backup memory he had kept in a time-proof safe to confirm his suspicions. Actually, reality was reassessing itself, showing the "true timeline" for split seconds. They simply had good enough reflexes since they are robots. Usually to be able to remember the previous timeline you have to be the one who changed it in the first place, or the focus of the change, the latter necessitating a shock to jog their memory; anyone else has to check the Ripple Effect Proof Database.
    • Also, said database, created by the Time Police. In theory it's just a recording of history, but in practice, being kept outside of time, it's immune from alteration of history, so whenever an illegal time traveler alters it the confront with the report from their surveillance droid will alert them at once, allowing to deploy a team to restore the right timeline at once (as seen in "The Day of the Cold Sun": as soon as Lyla failed to report her own destruction in the accidental nuking of Duckburg, a team of Time Cops showed up armed to the teeth). In fact, the rewriting mentioned above was possible only due a mutiny of a group of the surveillance droids themselves.
  • Humorously averted in Alan Moore's one-off "The Disturbed Digestions of Doctor Dibworthy". The titular scientist invents a Time Machine and tries to test it by making at first minor, and progressively more drastic, changes to the past. Each time he does, the narrative helpfully informs us that nothing changes, while the artwork shows the results of massive changes to history. Doctor Dibworthy does briefly consider that his own memories are altered as a result of changes to the past, but dismisses that idea as unlikely.
  • The Eleventh Doctor demonstrates this ability in the second issue of Star Trek: The Next Generation/Doctor Who: Assimilation², stating that he can feel his memories changing, as until he laid eyes on Worf, he didn't know what a Klingon was, though moments before he correctly identified Worf as such without prompting.
  • Notably averted in Les Légendaires; when Jadina uses a Reset Button to erase all the events of the Time Travel story arc in Books 5 and 6, none of the protagonists, including herself, apparently retain memory of the events. She only gets a feeling of Déjà Vu that doesn't last long.
  • Played with in the case of Justice Society of America villain Per Degaton. He's not supposed to remember his failed exploits as a Conqueror From The Future because of his time machine's Reset Button, but every time the night before his fateful encounter with the machine takes place, he has a dream that fills him in on all of his prior exploits.
  • Explicitly averted in Rat-Man: when Valker and Topin possessed by the Shadow create a machine capable of rewriting history, Topin states that nobody in the new reality without superheroes will remember the change, because it will always been like that. This is then brought to the logical consequence: in the new reality Valker thinks that, had superheroes existed, his mother wouldn't have been murdered, so recreates the time-altering machine and rewrites reality so that superheroes have always existed.

    Fan Works 
  • Time Travel stories are rife in the world of Harry Potter fanfiction. One almost universal common factor is that no matter how much the timeline changes, Luna Lovegood remembers the old one and has no problem with the idea of multiple timelines existing.
  • Ichigo has this for the most part in Hogyoku Ex Machina after time traveling. The exception is he can't remember Senna from the first film. Since Ichigo spent all of his time after Rukia's rescue in Soul Society instead of going home, she never forms in the first place, and so he doesn't retain the memory. He doesn't know anything about her until some Applied Phlebotinum shows it.
    • Kurotsuchi Nemu actually discusses this with Ichigo, saying that him and Aizen basically have a "shared hallucination" of the future/events and Ichigo's actions have changed the timeline pushing it into an Alternate Universe.
  • Played with in the My Little Pony: Friendship Is Magic fanfic Make a Wish. When a wish-granting comet passes by Ponyville, Rainbow Dash wishes for a chance to spend time with the Wonderbolts and the next day finds herself winning tickets from a contest she knows she never entered, only to be told she visited the contest's promotional office on a weekly basis to see if there'd been a winner. In the same vein, she never even suspects the fact she's been raising her little sister Scootaloo alone for ten-plus years is the result of Scootaloo's wish. Scootaloo, for her part, is fully aware of how she changed her own history and spends time worrying about the For Want of a Nail implications and the fact she doesn't remember the life with Rainbow Dash that Rainbow does.
  • Queen Of Shadows: Jade remembers the way the world was before her struggle with Shendu damaged the Book of Ages and altered reality. It's currently unknown if Shendu himself remembers as well, and Jade is worried of the ramifications if he does.

    Films — Animation 
  • In Meet the Robinsons, Lewis retains his memory of his entire adventure, even though through the course of the adventure, he takes several steps to prevent the film's villains from existing. Logically, this would mean the entire plot of the film never happened, though not addressed in the film itself. He's a really good inventor.
  • In the Young Wizards series wizards can change the past without Time Travel, by magically invoking a Reality Bleed from an Alternate Universe where the past worked out differently; only wizards will remember what the past used to be like. This is very useful for maintaining the masquerade.

    Films — Live-Action 
  • Naturally, the Back to the Future trilogy. It is a bit strange though, that while memory is proof against the ripple effect, ontology is not: Marty remembers his own timeline in the first movie, and yet he comes close to fading out of existence as history is pushed off-track. It may be that in BTTF, memory is not proof against the ripple effect per se, just a bit insulated from it, and like Marty's photograph, will fade slowly as the timeline diverges. Or it's just a big Timey-Wimey Ball.
    • Marty almost fades away in the first film because he almost changes the timeline to one where his parents never got together and thus he was never born. The timeline he ends up creating by the end of the movie is one where his parents DID meet but under different circumstances and thus he WAS born, but his parents are happier. If memory and ontology were both immune to the ripple effect, then what would be left to change as a result of time travel?
    • The lack of an alternate version of Marty is averted, however. It is implied that there is an alternate version of Marty in the new timeline, but Marty never meets him because Biff sent him Off to Boarding School. If that Marty really existed, it'd mean Marty would meet an alternate self in every reality he created.
    • In the novelization of Part III, it's also implied to work in the other way. Marty gets help from 1955 Doc to go back to 1885 and save the 1985 Doc. When he gets there, 1985 Doc asks him not only how he got there, but also who dressed him in such ridiculous clothes. Marty says that 1955 Doc did. At which point Doc remembers. That could just as easily be explained as Doc not really remembering (to him) a 30-year-old minor event until Marty reminded him.
    • In another example, (aided by a change in casting) when Jennifer comes to Marty's house the next morning, wanting a ride in the "new" pickup, Marty recognizes her, although she (obviously) looks different. Possibly her parentage was slightly changed, but now Marty grew up with this Jennifer so he reacts as he always does, not stopping to think "Whoa, what happened to you?"
  • Happened in Source Code. The protagonist is on a mission to stop a bomb from blowing up a train. He has 8 minutes. Every time he fails (and hence dies), when he is reset, he remembers what happened in the previous run. This is Justified by the nature of the Source Code. However, there is an interesting twist at the end.
  • The Butterfly Effect However, it should be mentioned that each time the protagonist changed the past, he received the memories of his own life (in the new timeline) up to the present. However, the memories weren't just there — they arrived as a searing burst of information (being physically written into his brain), and co-existed with his old memories, giving him a Psychic Nosebleed.

    There is one scene where another character has ripple-proofing, despite the fact that they shouldn't; the protagonists goes into the past and impales his hands on some spikes, to give himself stigmata in the present, so he can prove to his friend he's not lying. To his friend, they seem to have just appeared, which didn't happen to any other character in the film.
  • Frequency gives this a Hand Wave; after the main character inadvertently changes the past, he talks about how he sort of remembers it both ways. Though this is then dropped for the rest of the film, where he only remembers the original timeline after his mother is killed in the past, and a few other changes happen from his attempts to fix that.
  • The disadvantages of this are touched on at the end of Time Cop, where the hero is surprised to learn he now has a wife and son….
  • Sandra Bullock's character in The Lake House seems to have this. The film is one big Timey-Wimey Ball. The film could have been a knotted Stable Time Loop if there wasn't that one tree and if the filmmakers hadn't gone for Happily Ever After in the last reel.
  • In the Disney film Minutemen, the time travelers have this, but the people who asked them to change the past don't. Fortunately, they thought of this, and took a video of something that was never going to happen with them to the past. Apparently, even inanimate objects have this ability!
  • Godzilla vs. King Ghidorah, the only Godzilla movie so far to feature time travel, uses this trope. After the timeline has been altered in World War II so that King Ghidorah attacks Japan for decades instead of Godzilla, the main characters note the difference. Later when it turns out that Godzilla does still exist in this universe except bigger, they note they are the only ones who can identify him and realize the change in size. The filmmakers seem to have forgotten this when they made Godzilla vs. Space Godzilla and everyone acts as if the timeline never changed and Godzilla hasn't been replaced with Ghidorah, as evidenced by Godzilla vs. Biollante being mentioned...yet references to Ghidorah are made and Godzilla is still at the larger scale.
  • Star Trek: First Contact. The Enterprise can see the Borg!Earth timeline, but since they're in the wake of the time disturbance caused by the Borg Sphere, they're unaffected. It's strongly implied that they'd vanish from existence had they not went through the time aperture themselves.
  • Agent J has a ripple effect-proof memory in Men In Black 3. The actual mechanics of the effect in question are explained: you're immune to any changes in the timeline generated by alterations to an event which you were personally present atnote . There are also specific symptoms of the effect: you get a headache and an inexplicable craving for "chocolatized dairy products".
  • Brazilian film O Homem do Futuro (The Man from the Future) has protagonist Zero accidentally going back 20 years to the prom that ruined his life. So he tries to Set Right What Once Went Wrong, and vanishes as history is changed, waking up back to the present day... where he became rich, but is a Jerk Ass and the love of his life hates him. So he goes back again, and after leading things to go back the original way he vanishes again... returning to 2011 with memories of the entire time travel ordeal.
  • In Galaxy Quest, after Jason Nesmith activates the Omega 13 device, time turns back 13 seconds into the past. Jason alone remains aware of the fact that the person who is about enter the bridge is not really Tech Sergeant Chen but actually Saris in disguise.
  • The Philadelphia Experiment II. When a time travel accident changes history so Nazi Germany won World War II, the protagonist David Herdeg keeps his memories of the original Real Life timeline.
  • In About Time only the person who makes the trip back in time possesses this. Tim's dad is a time traveler too, but doesn't remember the changes Tim makes.
    • At one point Tim travels back with his sister (who can't travel back in time on her own). When they return to the present her memory is affected (she suddenly knows she is in a different relationship in the altered timeline) but she also retains the knowlege they time travelled in the first place.
    • In one conversation with his dad, Tim guesses that his dad may also have gone back and replayed it, and his dad confirms this. One wonders what'd happen if Tim and his dad really wanted opposite things from a conversation: would they both keep replaying it, flip-flopping the outcome, ad infinitum?
  • In X-Men: Days of Future Past, Wolverine is told up-front that he (and only he) will remember the Bad Future should he succeed in changing history. In the end, he wakes up in the "good future" with his memories diverging from real history since it was changed in 1973.

    Literature 
  • Time travel is used several times in Animorphs:
    • Book 11 has Jake, the narrator, being the only one who remembers the alternate timeline. This is explained as him dying in the alternate timeline, causing his two consciousnesses to snap together and allowing him to undo it.
    • Explicitly referenced in another book in the series, when the Drode first "restores" the Animorphs' memories in a way that lets them still remember the last five or so minutes of conversation but not any other details about the world in which they now live, then mentions that their memories will be "buffered" as they follow Visser Four through history. The Time Matrix also seems to confer this ability on to everyone who uses it (at least for changes they make using the Time Matrix), including Visser Four himself.
    • Cassie is shown in Megamorphs #4 to be a temporal anomaly who has this ability by default—if her timeline is altered, she gradually becomes aware of the discrepancy and subconsciously causes the alternate timeline to fall apart.
  • Robert A. Heinlein's The Cat Who Walks Through Walls has an incident where the protagonist is told a nasty event from his past has been removed, thanks to time travel. He protests that he still remembers it, but this is explained as "a memory of a memory", which will fade.
  • The third book in The Dark Tower series subverts this. Roland is going insane because he was remembering two timelines, one where Jake died, and one where he didn't. Jake was having an even worse time about it.
  • In Dirk Gently's Holistic Detective Agency, time is altered to destroy most of Coleridge's poem "Kubla Khan" (which now ends at the line "And drunk the milk of paradise"), in consequence preventing a murder and the retroactive destruction of humanity, as well as introducing a composer named Johann Sebastian Bach. Only the time-traveling main characters remember the original reality.
  • Intentionally invoked in Night Watch. Thanks to narrativium, history is mutable and subject to popular perception, so it doesn't matter if Vimes' memories of the "original" version are different as long as events play out roughly the same.
  • This plays a big part of the plot of A Game of Universe, as the protagonist has not retained his memory, only occasional "afterimages" he can see with magical vision. He doesn't realize any time travel is happening until the person responsible shows up and explains that the only reason the protagonist is alive is because he's been hitting the Reset Button every time something goes wrong.
  • In The Golden Spiral, only Abby remembers how things were "supposed" to be after Zo starts messing with her past- erasing her best friend, her sister her father, from her life. explained because she's been "outside" of time. she can also sense when he changes something. later she learns that she can "fix" someone in reality( the can't be altered) and restore their ' true' memories by taking a real photograph- not digital, but film.
  • Justified by Chronos in the Incarnations of Immortality series. As the Incarnation of Time, him and his memory would be impervious to any ripple effects. (Within reason: He isn't allowed to affect the past in a way that would prevent him from becoming Chronos.)
  • In John Dies at the End, the Living Shadow monsters regularly jump around through time and change things for sinister, unknowable reasons. However, random people end up with memories from before the timeline was changed.
  • In Johnny and the Bomb everybody but Johnny forgets their time travel experiences, although Kirsty remembers them again after finding a piece of physical evidence.
  • In The Lathe of Heaven, George Orr is the only one who knows reality has changed. That makes sense, as his dream causes it. It is also discovered that anyone in the room with him when he is hypnotized into dreaming a change also knows it. That makes slightly less sense, although since his subconscious is involved and the method used is not machine based, it certainly is possible. Even though other people with him can know, they are still not sure it happens unless he reminds them or it is a major change (like 90% of the population dies).
  • The eponymous Nobody in Nobody Gets the Girl is a product of this for most people when they experience this fade away. But the limitations are he can't be seen by anybody who doesn't believe he is there, and he can't move objects when he is being observed by someone who can't see him. But he can be observed by video cameras.
  • While it covers dimensions more than time, all Travelers in The Pendragon Adventure retain their memories of how their worlds used to be. Their acolytes are the same. This is a good thing, because starting from around the seventh book of the series, the world begins to change severely.
  • In Ray Bradbury's A Sound of Thunder, several time travelers to the past realize that they have changed history when they return to the future and notice changes that no one else recognizes.
  • In The Stainless Steel Rat Saves the World, Ripple Effect causes your memories of the other timeline to change rapidly. If you don't exist in the present timeline and you forget who you are, you fade away! The Special Corps created a countermeasure in the form of a device you stick on your head that reminds you of who you are every few seconds to keep you from vanishing outside your own timeline. Since the time machine he was using to Set Right What Once Went Wrong could only carry one person (him,) Jim took several other scientists' devices to temporarily overwrite himself!
  • In Star Trek: Department of Temporal Investigations, the titular department keeps records protected by phase discriminators, shielding the data from alterations in the timeline. Although the agents themselves will have no knowledge of the previous history, they can research their own files to determine if changes have been made. In the novel Watching the Clock, there's also a subplot that takes two of the protagonists to a Place Beyond Time, leaving their memories of another character intact when she suffers a Ret Gone.
  • In the concluding trilogy of the Sword of Truth saga, a spell called Chainfire erases almost everyone's memory of Kahlan, but Richard is protected because he was holding the Sword of Truth when the spell was cast. This is implied to be one of its original purposes, besides just being preternaturally sharp and conferring the skills of past wielders on the current wielder. Ultimately, the Boxes of Orden are the only way to repair the damage, and that was their original purpose. And the Sword of Truth is the key to the Boxes of Orden, making the counter to the Chainfire spell. Sword of truth, indeed.
  • Inverted in Tempest: A Novel. Jackson remembers the new timeline when he jumps, but the original timeline never changes.
  • John Barnes's short story Things Undone varies this depending on the size of the changes made. If something small changes, certain antisocial people will only remember the way the world used to be, and everyone else will only remember what it becomes. It turns out a big change initially leaves those antisocial people with conflicting memories. If they become more social, integrating themselves into the flow of events, they'll wind up with both sets of full memories. If they stay withdrawn, however, the universe will eventually erase them.
  • Used to blackmail the title character in the Thursday Next series when her husband is "eradicated" by the villains, and she is the only person who remembers him. Played with a lot along the way. There's even a therapy group for other people in this situation. (Everyone else just thinks they're insane.)
  • Robert Silverberg's Up the Line discussed this and other temporal oddities fairly well.
  • In Xanth, Lacuna wishes for a more interesting life, changing a big chunk of history in the process, but only she and a handful of others remember this.
  • One recent short story featured a American sniper who is equipped with an experimental time machine sent on a mission to kill Osama bin Laden before 2001, comes back and finds the situation worse (without bin Laden inspiring a spectacular, but limited, attack, the terrorists who did launch an attack were more careful and the result far greater). So he tries again, going a little further back in time, and the situation is even worse. So he tries again. And again, and again. After offing Mohammed didn't work, he's finally trapped in 1st Century Palestine when his time machine breaks after trying to kill Pontius Pilate.
  • The time-traveling protagonist of Ward Moore's novel Bring the Jubilee accidentally ends up changing the outcome of The American Civil War from a Confederate victory to our own time-line. He remembers the previous history, but is stranded in our version of reality and lives of the rest of his life here.
  • In Rebecca Lickiss's Eccentric Circles, characters can remember what existed before it was rendered Ret Gone by the rifts.
  • The Dean Koontz novel Lightning has a complicated example. The traveler goes into the future and falls in love with a crippled woman. He then goes to her past (still his future) and prevents the crippling incident from happening; thus the later future that he visited no longer exists. He protects her in this way several times and eventually arrives at the timeline in which most of the book takes place, but he can still tell her about all of the other timelines that he visited.
  • In Pact, which is filled with creatures that toy with the memories of others, Isadora the Riddling Sphinx is proof against most memory manipulation, as remembering is part of what her kind was designed for. She can even stand against an effect that renders the person it hits an Unperson; though she'll usually lose a good amount of information about them personally, she retains enough to put the pieces together and describe their basic personality.

    Live-Action TV 
  • Doctor Who
    • In "The Time Meddler", the Doctor's companions suppose that, should the Monk succeed in changing history, their own memories would instantly change. While this might seem to exclude the Doctor from this trope, the balance of evidence points the other way, and there's no way for the companions to be doing anything more than guessing. Of course, many fans will angrily tell you that "The Aztecs" conclusively proves that you can't change history at all in the Whoniverse, so the question is moot. Both examples require that you discard the overwhelming evidence in the other direction, of course.
    • The closest the new series has gotten to a definitive stand on the issue is to say that the Time War was "invisible to lesser beings, but devastating to higher forms." The Word of God, so far as anyone can piece together from various comments, is that more highly evolved species, particularly the temporally active ones, have ripple-proof memory. Whether similar status is conferred upon humans who have time traveled is likely but uncertain. Comments by Russell T Davies explicitly name the Time Lords, Daleks, Gelth, Nestene Consciousness, and the Forests of Cheem as "higher beings".
      • In Flesh and Stone, it is explicitly stated, first through events, and later through dialogue, that a time traveling human gets ripple-proof memory too. "You're a time traveler now, Amy. Changes the way you see the universe. Forever. Good! Isn't it?"
      • They also establish, though, that this mostly applies to timeline changes from outside your own era, which is how Amy forgets about Rory when he's 'eaten' by one of the time cracks.
    • Last of the Time Lords: In what is known to Whovians as The Year that Never Was, characters aboard the Valiant experience this; it is explained that their proximity to the Paradox Machine allows for this.
    • The Stolen Earth: A representative of the Shadow Proclamation explains that, in the wake of the Time War, the lesser races only know of the Time Lords at all from "legends passed down from the higher beings".
    • Cold Blood adds a further complication: if a change to history undermines a time traveler's own personal history, they are only partially protected: the relevant memories will change, but the traveler can resist this through concentration. Or so we're told: the traveler in question fails to resist the change, so it is not clear that this ability is anything more than theoretical.
      • The Big Bang adds yet another wrinkle: growing up near a crack in time can do unusual things to someone's memory. If they end up having their personal history changed, the original memories will still be present, buried in their subconscious. This effect remains even if they become a time traveler.
      • The effects of proximity to a time crack are all-but-confirmed in "The Wedding of River Song", where Amy is again able to retain memories of timelines that never were.
    • Going along with having one's personal history changed, The Day of the Doctor features three Doctors meeting and pulling off a combination of Screw Destiny and Tricked Out Time to prevent what they see as their greatest failure. Their meeting and actions cause the timelines to go out of sync, causing only the "oldest" of the three Doctors to remember events.
    • In the Zagreus arc of the Big Finish Doctor Who audios, the Neverpeople, Gallifreyan criminals sentenced to removal from history, retain their memories of the timeline that had been theirs, while the rest of the universe — including the people responsible for their removal — have no recollection of them. One strange side effect is that the Time Lords believe that this particular method of execution has not been used in eons, since, in the resulting timeline, its victims never existed in the first place. The problem is that there are records resistant to the changes imposed by the chamber, and when the person who has routinely authorized its use hundreds if not thousands of times has a good look at them, she's so overcome by horror and guilt she enters the chamber willingly.
  • Journeyman
    • A number of episodes deal with Dan himself, such as when he meets his own father on the day the latter planned on leaving his family. Dan convinces him to talk to his sons about it, so they don't end up blaming themselves in the future. When Dan goes back to the present, he asks his brother about that night and finds out that their father did indeed explain everything to them before leaving. Additionally, when Dan accidentally leaves a digital camera in the past, he comes back to find that not only has computing technology skyrocketed (nanotech is ubiquitous), but his son is now a daughter. He ends up restoring the timeline, despite his wife's objections. Luckily for him, she doesn't remember anything.
  • Stargate SG-1 ("2010", "Moebius") and Stargate Atlantis ("Before I Sleep", "The Last Man"). Both follow the logic which states that the time-travelers should have alternative counterparts in the new timeline. Their earlier counterparts always seem to conveniently end up dying.
    • In Stargate Continuum, a Delayed Ripple Effect almost gets the team (minus the already-erased Teal'c and Vala) before they enter the Stargate. It turns out being in a wormhole at the time of the ripple effect makes you Ripple-Effect Proof. Who knew? Unusually, this example shows alternate versions of the man characters, except two — one was never born, and another died a hero some time ago. A third is only ever "seen" from the wrong side of a phone line.
    • In "Window of Opportunity", O'Neill and Teal'c qualify. Might be partly because time technically kept going, and the looping turned out to be somewhat selective.
    • In "Moebius", actually, the team didn't remember the time that they had erased once they set wrong what once went right. But their past selves had made a video tape to deal with this very problem, which convinced each of them that time travel had occurred and they needed to change it.
  • Star Trek, being deeply in love with time travel, has had many examples of this:
    • An example where this occurs to characters who didn't time travel: "The City on the Edge of Forever" from Star Trek: The Original Series. Hand Waved later on as being due to their proximity to the Guardian of Forever.
    • The New Voyages fan episode In Harm's Way treads similar ground; history is altered such that the Federation is fighting a losing war against a fleet of Doomsday Machines, and Kirk and his crew are stationed aboard the USS Farragut, with a Klingon first officer. Only Spock, who was engaged in studying the Guardian of Forever when the change took place, remembers the way things are "supposed" to be.
    • Lampshaded in the Star Trek: Deep Space Nine episode "Accession": Kira mentions an unfinished work of a poet who disappeared long ago. Sure enough, he shows up five minutes later. By the end of the episode, he's been sent back in time, and she's shocked to discover that the poem is now finished and again shocked that she remembers it ever being unfinished. "The Prophets work in mysterious ways."
      • Lampshaded again when the Deep Space Nine cast visits "The Trouble with Tribbles". Sisko complains that if he changed time, he would have been the first to notice. The Time Agents complain that people always say that. (Thankfully, he didn't change time in any significant fashion. Probably.)
      • Odo did bring a tribble back with him — when they had already been driven extinct, which is not a temporal paradox of any sort (and harkens back to Kirk's saving of Humpback whales in Star Trek IV), but would almost certainly constitute a violation of whatever laws the Federation has regarding the transport and breeding of endangered and/or environmentally dangerous species. Given the history of Klingon interaction with tribbles, it might even have led to a major diplomatic incident..
      • Another Lampshade in Visions when Past!Miles is warning Future!Miles about a disaster.
        Future!O'Brien: You look pretty bad.
        Past!O'Brien: It's the radiation.
        Future!O'Brien: But if you feel bad and you're my past self, shouldn't I feel bad too?
        Both: (in unison) I hate temporal mechanics.
      • In Star Trek Online, there are "Tribble Extermination Squads", which is considered one of the lowest positions a Klingon can hold, short of being kicked out of the military altogether.
    • In another episode of Deep Space Nine, Sisko, Dax, and Bashir are sent back to a tumultuous period in Earth's history and inadvertently change things such that civilization collapses. The ship in the present from which they'd departed was shielded from the timeline alterations by the same effect that sent them back in time. As before, they return to find history only mildly altered (in this case, a historical figure now bears an uncanny resemblance to Ben Sisko).
    • Two similar episodes from Star Trek: The Next Generation ("Yesterday's Enterprise") and Star Trek: Voyager ("Time and Again") feature history changing without anyone remembering it, but with the local telepaths/mysterious wanderers having odd feelings about something being out of place.
    • There's also the TNG episode Cause and Effect, in which the Enterprise gets itself trapped in a time loop and end up repeating the same day over and over. They DON'T know they're repeating it however, until various hints and a creepy sense of déjà vu start becoming apparent, and they catch on:
    Riker: You mean we could've come into this room, sat at this table and had this conversation a hundred times already?
    The crew are then (somehow) able to send a single one word message into the next timeline via implanting a message into Data's positronic net, thus giving them a one-shot chance at changing the future and avoiding the loop - all they could send was one single word, and hope that would be enough for Data to get the hint and change future events.
    • No one remembered history changing back from "Yesterday's Enterprise", either — it seemed to those aboard the Enterprise-D that nothing had happened. But the round trip of the Enterprise-C had an unintended consequence which would surface for a later season.
      • It's not clear just how much Guinan remembered of the timeline change: she calls the bridge to make sure everything is OK and then asks Geordi to tell her about Tasha Yar. In the original script of "Redemption, Part II" she says she has a vague memory of Tasha asking her something.
      • Guinan likewise had flashes of the "proper" timeline in the alternate one of that episode. Guinan's time-sensitivity is eventually explained in Generations as a side-effect of the "time" she spent in the non-temporal world of the Nexus. Whether this means Picard is now ripple-proof as well never got explored.
      • Guinan is also a Ripple Effect proof person as well. Despite the new war timeline meaning the Enterprise is staffed entirely by military and all the children and civilians are gone (because you'd obviously not bring them on a ship constantly in battle) Guinan is still on board as the only non military member running Ten Forward despite the rest of the staff being gone, and Guinan having no real job there because the alternate timeline crew survive entirely on military rations. Another clue to her that something wasn't right.
      • An Expanded Universe novel has several alternate realities converge. One of these is nearly identical to the reality in which the Enterprise-C disappears at Narenda III and travels to the future. However, in this case, by the time the Enterprise-D reaches it, the crew is already dead. They scuttle the ship so the Klingons don't get it and keep going.
    • A particularly convoluted example from a recent novel involved Scotty going back in time to save Kirk from "death" on the Enterprise-B. Since Kirk wasn't in the Nexus to be pulled out by Picard, the Enterprise-D was destroyed, and the Borg succeeded in changing history in First Contact. In the new timeline, only Scotty (and an accomplice?) recall the original timeline — and they're the only non-assimilated humans. Presumably the Borg know, but they aren't talking.
    • During the "Temporal Cold War" arc on Star Trek: Enterprise, Crewman Daniels, a time traveler from the far future, zaps Captain Archer to his own time to save him from capture by the Suliban. They both arrive on a devastated future Earth whose technology hadn't progressed even to TOS levels, where the Federation had never been founded (and, it's implied, the Romulan Empire became the dominant force in the galaxy). Archer doesn't understand how Daniels can still exist with his timeline so radically changed. Daniels claims not to know, but is also reluctant to go into the details of temporal mechanics with a person from Archer's era.
      • Yet another time change not having erased Daniels in "Carpenter Street" was explained as the ripple not having hit his century yet, but would if Archer didn't stop it. San Dimas Time.
    • The episode "Year of Hell" has Voyager going up against Krenim ship which is trying to restore the glory of their civilization by Ret Gone-ing others. Voyager's crew manages to devise shielding that protects it from the temporal waves generated by the weapon which change the timeline, which they share with other ships for an assault on the weapon. Then Captain Janeway orders everyone to turn theirs off while she rams Voyager into the timeship, just to make sure the Reset Button goes off cleanly. Ironically, this achieves the Krenim leader's goal as well; he'd accidentally ruined the Krenim empire (and RetGoned his wife) at the start of his temporal experiments and was desperately trying to undo the damage but never quite getting it right. With the timeship itself erased from history, his original mistake was also retconned away.
  • In Heroes, "Five Years Gone", Future Hiro remembers the timeline where Claire wasn't saved, but nobody else does. Interestingly, because Claire's survival is kept a secret from Future Hiro, he doesn't notice a difference between the timeline in which Claire was killed and the one in which she wasn't. Because of this, it's debatable whether he has Ripple-Proof Memory or not - because there's no difference, we wouldn't know if he previous memory was overwritten as soon as he sent Peter to save Claire.
  • Rimmer and Holly display this ability in the Red Dwarf episode "Timeslides".
    • Further, in "Angels & Demons", Lister mentions having "played pool with planets" as a point of reference for the remarkability of his first taste of an edible pot noodle. However, according to Kryten's explanation at the end of "White Hole", he shouldn't have been able to remember that. But that's okay.
      • As Kryten himself admits on one of the Smeg-Ups blooper specials, he was originally programmed to clean toilets, not explain things like DNA or time paradoxes. "In other words, I made a mistake. OK?!?"
      • He also says that no-one's ever seen a white hole before, so some of the theories about how they work (including not remembering things) might not be correct.
  • In Primeval series 2, Nick and Helen Cutter are the only ones who can remember Claudia Brown. Later, Jenny, the alternate version of Claudia, finds a photo of herself that she doesn't recall posing for. She realizes that everything Nick said was true.
    • Unusually, the altered timeline stays altered. By the time the latest season rolls around, the only people who remembered the original timeline are dead. Then again, it's been a long time since anyone cared about this. Even Nick stopped trying to change things and accepted the new reality.
  • Used in Mystery Science Theater 3000 episode 821 "Time Chasers". Crow, attempting to help Mike, goes back in time to keep him from getting stranded in space. When he returns, he learns that instead of Mike, he's partnered with his chain-smoking, beer-swilling Jerkass brother Eddie, who's whipped Servo into a quivering yes-man; only Crow remembers the original timeline, which he eventually restores.
    • The funniest part is that Eddie doesn't doubt him at all. He just gets pissed that Crow thinks their timeline "sucks".
  • In Terminator: The Sarah Connor Chronicles, the memories of time-travellers are apparently unaffected by timeline changes, as Derek Reese has flawless memories of meeting Andy Good in the future — despite the fact that, after travelling back to The Present Day, he murdered Andy, and their meeting thus never happened.
    • It's pretty clear that everything in the Terminator universe has Ontological Inertia, including people; John Connor doesn't vanish when the Machine War is averted in T2, nor do his mother's memories of Reese change no matter how much the War gets moved around (for that matter, the Kyle that Derek remembers probably isn't the Kyle that Sarah slept with, what with perturbations in the time stream, but John's genes don't change). In that universe, once something happens or exists, that's that.
      • Considering that the War wasn't averted, Reese still time traveled to save Sarah and conceive John.
      • Yeah, but the Reese that sired John traveled from a future where the war started in 1997. If Reese had to go back again, in the new timeline, it'd be a Reese who saw the war start in 2011. Essentially, a different person — conceivably, he could go back and find the grave of the earlier version of himself who died in the first movie.
      • This is easy: original Reese is from an alternate future, where the war began in 1997.
    • However, in at least one episode this is not the case: when Jesse kidnaps Charles Fisher from the future, she remembers Derek relating numerous tales of being tortured by Fisher, but Derek himself has no memory of any of that. They conclude that they are from two different futures.
      • The confusing thing is that while Jesse seems to think that she's from the 'original' future, and that she just saved Derek from torture and our Derek is from the new timeline, it ends up being pretty clear by the end that she has it backwards and our Derek is from the original future (Or at least an 'earlier' future.), and Jesse is from the new future that was just created by her kidnapping Charles Fisher. Regardless who is right, neither one of their memories change, because there is 100% Ontological Inertia in the Terminator universe, and changing the future has no effect on people who already went back in time.
  • Inconsistently subverted on Quantum Leap, where sometimes Sam remembers the unaltered timeline, and sometimes — as in the case of one change that resulted in his earlier self marrying the girl that initially got away — he doesn't. Some of this can be handwaved away with his "swiss cheese memory", but not all of it. The bulk of evidence suggests that if Sam's memory is changed at all, the changes only occur when he leaps. Al, however, always seems to remember the old timeline — that is, if he hasn't been erased and replaced by Roddy MacDowell, at least. It helps that he has Ziggy.
  • In the episode "What Ever Happened to Sarah Jane" of The Sarah Jane Adventures, an alien artifact bestows this power on whoever holds it at the "time" of the Ripple Effect.
  • In "A Stitch in Time," an episode of the revived The Outer Limits, an already-unbalanced scientist uses her time machine to go back and execute notorious serial killers before they hurt anyone. Each time history changes, and she remembers each and every change, driving her crazier and crazier. In the end, she (and a homicide detective following her murders) go back in time to save her younger self from the sexual assault which originally caused her problems. The scientist loses this (having essentially erased herself), but the detective gains it and realizes that her best friend was killed by one of the serial killers the scientist had no motivation to kill in the current timeline. The detective then starts killing serial killers...
  • In the Time Cop TV series, one episode has Logan and a villain accidentally altering the timeline in such a way that when they get back to the future, Logan is now a criminal mastermind and the villain is still in good standing with the police force. The versions of the characters that were just replaced had their own ongoing schemes—but the Ripple Effect Proof versions don't have a clue what's going on. This leads to such increasingly circuitous bouts of Fridge Logic between everyone's interactions that the show becomes So Bad, It's Good.
  • Angel, of the eponymous vampire-detective series, had an episode in which he dealt with the Oracles (Deus ex Machina disciples of the Powers That Be) to have a day undone and so that he was the only one who had memory of the events. In After the Fall, there's a Reset Button, but everyone in LA remembers the Hell on Earth. Eventually, most people not part of the masquerade become convinced that it was just a Shared Mass Hallucination.
  • Kamen Rider Ryuki: All Kamen Riders recruited by Shiro Kanzaki can have their memories erased when Kamen Rider Odin performs his Time Vent move. Since Shinji just stumbled onto his card deck, this makes him immune.
  • Mostly averted in the second season of Witchblade. At the end of the first season, Pez goes back in time to when the first season started. She doesn't retain any actual memories of the original timeline, but she does sometimes have a sense of when she should do something differently from the first time around, most notably the event in the pilot that got her partner killed; she avoids the encounter, and he survives season 2, but as a result, the main bad guy remains at large through the rest of the series.
  • In Kamen Rider Den-O, the Singularity Points like protagonist Ryotaro don't just have this, they have Ripple Effect Proof Existence, meaning that they can exist outside of time and changes to the timeline don't affect them at all; movie villain Gaoh needs an incredibly powerful MacGuffin just to kill Ryotaro and make it stick. This is a major plot point in several parts of the show, most prominently the mystery behind Yuuto Sakurai, who disappeared one year before the show and who has vanished from the memories of everyone who knew him - except Ryotaro, who is quite shocked when a teenager claiming to be Sakurai appears about halfway through the show as a rival Kamen Rider.
  • In Smallville, Clark travels backwards in time at least three times (once with a Kryptonian Crystal to save Lana's life, once with the future Legion of Superheroes' ring to undo his revealing to the world, and once to save himself as a baby in Krypton), and always remembers the timelines that no longer exist. None is longer than a day or two, so it's not a big deal. Also, this is Superman, so he's Everything-proof. In the lead up to the third example, Kara sent a message from past Krypton, which Dr Swan received in 1989 and recorded in his journal. Clark, reading the journal in 2007, notices the page is "new".
  • Charmed
    • When Cole changes the past, with the help of the Avatars, to ensure his conquering of Pheobe's heart (well not really), Paige "accidentally" sneezes in the middle of the ripple effect, ending up in the alternate present where everyone else forgot about her. They were actually aiming to remove her from continuity, and it technically worked, but her presence there destroyed Cole for good...until he came back, at least.
    • Another example: In the first season finale, Déjà Vu All Over Again, a demon repeatedly resets time to try to kill the Charmed Ones. Phoebe's power of premonition lets her retain some memories from each timeline, eventually remembering enough to defeat the demon.
  • Parker, the hero from Seven Days, was picked by Project Backstep for his high tolerance for pain and a photographic memory. He would be briefed on the event that needed to be changed and sent back to change it. Though neither he, nor other characters from the series have this ability. It did happen to a kid where the alien spacecraft went through a plane, who could remember the past seven days. Parker on the other hand, if he's not the one piloting the machine, forgets like the rest of them. This was actually the plot point of one episode, where Parker is about to be sent back in time, when he spits out the awful tea Olga gives him on the controls, causing a short which kick-starts the Backstep with only his duffel bag in the Sphere. Amazingly, the Sphere ends up in the same place 7 days prior, but all they find inside is the bag with a key (an actual key). They have no idea what needs to be stopped, so Dr. Mentnor re-enlists the help of a psychic whom he used once to try to resolve a hostage situation (the failure drove the little girl to a mental hospital). After touching the key, she starts getting glimpses of the future 7 days. With her help, the crisis is averted, although she does warn Parker to lay off Olga's tea.
  • The fourth season of Fringe is largely about exploring the implications of this concept. First with the adult version of Peter recorporealizing in an altered timeline where he died as a child, then with Olivia recovering her memories from the prior timeline at the expense of the ones that correspond with the current version of reality.
  • Eureka explores this to great effect several times. First, a season finale involves Jack traveling from the future to prevent all of reality from unraveling due to Henry previously going back in time to save his lover. In the following episode, he tries to ensure that his memories of his happy life with Alison come true, but inadvertently puts her off with his familiar attitude. Also, he notes that events are already changing, so the same future will no longer occur. Henry uses a device to erase Jack's memories of the future to spare him the pain, while keeping his own memories (of a slightly different future) intact. Then there's a whole season devoted to the main characters coming back from the 40s with Dr. Grant (who hitched a ride back with them) and seeing the changes made to Eureka. All of them remember the old timeline and try to keep quiet, as Eureka actually has protocols for just such an occurance. Henry is now married. Fargo is the head of Global Dynamics (partly thanks to his grandfather never having been frozen in the past in this reality). Alison's son is no longer autistic. Jack has never broken up with his girlfriend. Notably, the original timeline never gets restored, although Grant tries to alter it once again to no avail.
    • Interestingly, not only is the later timeline our timeline, but there was a hint that the original wasn't at least two seasons before it changed, as wormholes were called Einstein-Grant Bridges. Then Dr. Grant came forward in time, and after that they're called Einstein-Rosen Bridges (just like in our reality), presumably because Dr. Grant wasn't there to work with Einstein.
  • Averted in MythQuest. It is possible for the characters to travel into a myth and act it out, including a different ending. If that happens, everyone in the real world remembers the myth differently. While they don't remember what the myth was, they do remember that they changed it.
  • Audrey Parker of Haven is immune to the cursed powers of the town's residents, meaning that when reality goes sideways (versions so far include "Groundhog Day" Loop, Ret Gone, and Butterfly of Doom), she'll be the only one to notice things aren't normal. The Genre Savvy cast have learned to pay attention when she tells them about it.
  • On The X-Files in the "Groundhog Day" Loop episode "Monday", Agent Mulder managed to invoke this trope on his own by repeating to himself that there was a bomb right before the explosion - being in the same situation during the next loop triggered the memory.
  • Kicks off a plot arc on Warehouse13. Artie uses a cursed device to go back 24 hours and avert worldwide catastrophe; obviously, he arrives Just in Time to do so, and remembers what needs to be done. But the side effects aren't pretty.
    Pete: I’m not going to remember, am I?
    Artie: Remember what?
    Pete: Dying.
    • While Artie does rewind the time and change what was going to happen, the artifact he uses inexplicably disappears from its hiding place, which tips off Brother Adrian that something's up. Additionally, Helena gets suspicious and later correctly guesses what Artie has done, having some experience with Mental Time Travel herself (albeit in a You Already Changed The Past way).
  • In Legend of the Seeker, Zedd tries to cast a spell to "de-program" Cara, but it backfires and results in a new timeline caused by Cara never becoming a Mord-Sith and, thus, not leading the Mord-Sith and Darken Rahl to Richard as he was performing the Boxes of Orden ritual. Richard and Kahlan were able to complete the ritual and make the known world loyal to Richard. Richard becomes rules of D'Hara with Darken Rahl as his loyal advisor. Everything is great, as Zedd appears to be the only one who remembers the original timeline. Then it turns out that the Keeper remembers it as well, and orchestrates to break the power of Orden. Luckily, Zedd is able to get a Close Enough Timeline by using the same spell on another Mord-Sith (thus, undoing the first casting).
  • In The Worst Year of My Life, Again, Alex finds himself reliving the previous year, and he knows what's going to happen to him. Downplayed - he specifically says that he doesn’t perfectly remember everything that happened the first time around.

    Tabletop Games 
  • Feng Shui's Innerwalkers have this by default. Once someone has been through the Netherworld, they're removed from the timestream, and are thus unaffected by whatever changes are wrought by the chi of the world changing hands. They keep all the memories they have of what the world was like before entering the Netherworld, and thus do not have their memories changed like everyone else's when a shift happens. But the thing is, when something like a critical shift happens, the innerwalker can easily find himself as a much different version of himself from the new timeline, complete with a new name, new history, new enemies and the like, and no one who hasn't been through the Netherworld will remember anything but what the current version of the character is like, leading to serious Mind Screw. Innerwalkers who've gone through one too many critical shifts tend to retreat to the Netherworld full-time, no longer able to deal with living a life they can't recognize with loved ones they've never met.
    • A pretty good (and amusing) example is given in a supplement of two Innerwalkers who barely knew each other. A critical shift hits, and they find themselves world famous... and married. They're living together now, to keep up the celebrity mega-couple act, and are quite surprised to be slowly falling in love. The shift does suggest that if they had known each other, they'd get married, and they're sure getting to know each other now.
    • Some of the fluff fiction in supplements have characters changing equipment and abilities in a critical shift; a character with arcanowave schticks ending up without the implants and with different schticks after arcanowave tech is eliminated from the timestream, for instance, even though their memories remain. It contradicts the actual rules on what happens to Innerwalkers, but Feng Shui always does play a little fast and loose with rules.
  • This also can be purchased as the advantage of Temporal Inertia in GURPS.
  • In the AD&D 2E supplement Chronomancers, time traveling characters are vulnerable to changes made to their past — and aren't able to do much to prevent it, since they can't travel to a time they've already lived in. However, the supplement also includes a high-level spell that severs your personal time line, making it so you were immune to any changes made to your past, and so you could overlap your own past.
  • In Mage: The Ascension Czar Vargo (a powerful Steam Punk Mad Scientist mage with a bit of an idealistic bent) attempted to prevent World War One with an unprecedented global display of the power of his technomagic. He pushed reality so far that when it snapped back it erased all memory of him from existence, and to this day the only knowledge of him comes from a tiny handful of eyewitnesses who retained their unedited memories of the event.
  • History in Genius The Transgression has been accidentally changed in radical ways a few times despite the best efforts of various groups to preserve the timespace continuum, although neither the general population nor reality itself generally seem to notice. This means that some of the most spectacular world-changing events in the game setting only happened in continuities that no longer exist, and are only remembered by time travellers and a few other scattered people who somehow manage to remember them. As well as a few not so world-changing events, like each and every one of the successful Hitler assassinations.
  • The 1980's time travel game Timemaster used a version of this. When history is changed, everyone including the PCs remember the changed version ... but if the PCs make their "Paranormal Memory" roll, they also remember the original timeline.

    Theatre 

    Video Games 
  • In Achron, you play a general precisely because of your nature as an 'achronal': an entity outside of time and unaffected by changes to the timestream.
  • Link (and Tatl) in The Legend of Zelda: Majora's Mask. Possibly the Happy Mask Salesman as well. Probably justified since the Goddess of Time is the one enabling them to travel back in time.
    • Also the woman running the Clock Town Bank. She is able to recall your name and how much you have deposited, before you technically first deposited it, by looking at a mark on your hand which, once applied, never appears to be changed, meaning it cannot possibly have up-to-date information on the rupees you haven't actually deposited because you reset time.
  • One of the most interesting aversions of this trope is The Journeyman Project games. The main character is a member of the titular Journeyman Project, a government agency which was created in response to the emergence of time travel technology to keep history from being changed. Changes in time create a temporal distortion that travels only forward in time from the moment of the change. One agent is constantly on duty to monitor for such changes; in the event that one occurs, the agent time-jumps back into the time of dinosaurs, a period of history considered "safe" because any changes would wipe out humanity. A record of all events in human history is kept there and can be referenced against a similar record in the future. The differences allow the agent to pinpoint the focal points and prevent the changes. The only reason this works is because the agent and lithmus record are not actually subjected to the ripple.
    • Only the first one, technically, although this is generally averted. In the later entries, it becomes possible to detect changes to the timeline without the archive disc. The latter is part of the backstory of The Journeyman Project 2: Buried in Time, where Gage Blackwood (the first game's unnamed Agent 5) is falsely accused of tampering with history for personal gain; the evidence against him consists of mini-temporal distortions originating from several time periods he visited. In the opening of the third game, Agent 3 tries to get the TSA's attention by leaving her Jump Suit time machine behind, setting off a massive temporal distortion.
  • Anyone in Time Hollow for the DS who either owns a Hollow Pen or was pulled through a Hole has this. Used as a bit of a running gag with one character who introduces himself to the main character every time they meet, since the main character meets him about once per chapter, and undoes their meeting at the end along with everything else that went wrong that day.
  • The main party in Chrono Trigger. Anyone that time-travels, for that matter. The fansite "Chrono Compendium" calls this phenomenon "Time-Traveller's Immunity", and extends it to include total immunity to any change that occurs due to their own travel. (Except, oddly, at the beginning of the game when Marle prevents her own birth accidentally and subsequently disappears (there is also a joke alternate ending where everyone is turned into a Reptite. But that seems to be the exception in the game, not the rule.)
    • The most commonly accepted theory is that it was done by The Entity in order to set the rest of the games events in motion. There's no Word of God on it though.
  • A weird related effect occurs in Mario & Luigi: Partners in Time. At one point, you end up altering E. Gadd's memories of the past. He's susceptible to this, but somehow realizes it's happening.
  • Montague Castanella of City of Heroes gets this as a superpower. He was already a proficient mage before he realized he had this ability; there wasn't a reason to suspect he possessed it until the Time Police showed up.
  • In Dark Cloud 2, Monica, the time-traveler from the future, naturally retains her memories of what said future should have been like until Griffon destroyed it from the past. As she and Max work together to restore the future (well, future from Max's perspective, but Monica's past) they run into a small bit of Time Travel Tense Trouble (for instance, they must create the origin of a factory that Monica remembers as having provided technology to a lab, even though neither the factory nor the lab exists yet.) As they restore these "origin points" and more elements from these locations reappear, inhabitants of restored future villages have no memory of what should have been there, but they do feel that "something is missing" until the village is completed. In the most notable case, a king from the future is astonished at a change in history he doesn't remember, but that Max's mother Elena, his contemporary, recognizes it as an improvement Max and Monica made in the past's future known timeline (implying that she is aware of, and remembers, both the original and the improved one.) Meanwhile, their flunkies just roll with it, and presumably their memories were rewritten along with history.
    • And it goes without saying: although the Big Bad is defeated in the present (Max's time,) monumental events threaten the world (the Blue Moon turns into the Star of Destruction, and falls from the sky,) and remains of the battle stay there (such as the Moon Flower Palace, crashed just outside Palm Brinks) the good guys from the future have no knowledge of any this until it actually occurs.
  • Averted in Cross Channel. Taichi and Youko often figure out what's going on, but that is because there is one spot that doesn't reset at the end of every week. Records of past Taichis are kept here. Miki at one point or another also discovered this and began hiding inside it every Sunday in order to avoid the resets. However, Nanaka DOES remember all the past weeks. But, as Taichi notices, she's not really 'there' and isn't exactly looping like the rest.
  • This comes with the Reality Warper abilities of the Star Singers in Final Fantasy Crystal Chronicles: Ring of Fates. It only applies to the one doing the altering at the time. The multiplayer mode however demonstrates that powerful entities, even if they have current timeline versions, can leak through. One even returning as a boss in the original Crystal Chronicles, and the current versions may have déjà vu (or in one case a relapse) of their previous selves.
  • In Legacy of Kain: Soul Reaver 2, Kain is seen in clear anguish as new memories flood his mind after a substantial Time Paradox takes place, realizing that in changing history, he and Raziel did exactly what the Hylden wanted them to do. Not exactly averted as Kain still seemed to remember the original timeline, and that's what was causing his anguish and allowed him to give Raziel one last piece of advice to avert the change, which Raziel didn't heed.
  • Played straight in Singularity as Renko as well as everyone on the island is perfectly aware of what is happening to the timeline. This is what allows Barisov to attempt to fix the timeline.
  • Star Trek Online, being a veritable fountain of Continuity Nods, naturally ends up featuring this in some way. The most prominent example is likely the "Past Imperfect" storyline, which involves the Guardian of Forever granting Ripple Effect-proof memory to the player's crew due to proximity. There are also some unusual examples, in that Present!B'Vat doesn't seem to recall his past self's Future Me Scares Me moment, where he effectively betrays himself. It also leads to some fairly amazing Tricked Out Time, Stable Time Loop, etc. moments.
  • The fact that Tatsuya didn't give up his memories in Persona 2: Innocent Sin sets up the entire story of Eternal Punishment where the world may end again because of his desire to protect his Cool Big Sis / Love Interest Maya.
  • This is a major character point to Rachel (and by proxy, her butler Valkenhayn) in BlazBlue, who remembers over 72,500 years of looped time. It is also shown that Hazama/Terumi shares this ability in the second game.
    • It might also be a Deconstructed Trope, as it is heavily implied that Terumi, who has lived through FAR more loops than Rachel, eventually snapped and decided to pay the world back for every single loop he had been forced to relive in it.
  • Dissidia states that the warriors are kept called for the next cycle of war - the side that lost will have no memories, though, while the winning warriors remember their last battle.
  • This happens to anyone Sissel helps in Ghost Trick (by way of going back in time and preventing deaths), himself included. Granted, the end of the game leaves us on a note where the player (with the help of three other ghosts) just prevented the entire game from happening, so no one remembers except Sissel, who is still dead—kind of—at the very end, and the other ghosts, restored to their natural lives.
  • You, the protagonist, have this in Millennia Altered Destinies by virtue of piloting the XTM, a hyper-advanced Cool Ship capable of traveling through space/time and powered by gravitational energy. Any time you change something, your ship shakes, and your on-board AI warns you of an incoming Temporal Storm. As it happens, you can watch the onboard historical database of the Echelon galaxy and it will instantly change the moment the XTM is hit by the storm. The database is intentionally not shielded from the ripple effect, allowing you to see the outcome of your changes. According to Word of God, the game originally had a Nonstandard Game Over triggered when you would make a change making the game unwinnable, resulting in a massive Temporal Storm destroying the XTM. However, when they realized that such an event was impossible given the mechanics of the game (you can always undo what you've done), they removed this option. The goal of the game is to guide four races to prosperity in the Echelon galaxy by intervening in their histories and setting them on the right course.
  • In Final Fantasy XIII-2, Serah and Noel remember all of the separate timelines they create and can move between them at will. Noel's memories of his own time aren't so ripple-proof. The more the main timeline is changed, the more of his life Noel forgets. It's heavily implied that he's being erased from reality... and his presence at the end of the game is a major indicator that things are about to go horribly wrong.
  • This is a gameplay mechanic in games like Braid and the Prince of Persia Sands of Time Trilogy. Temporarily reversing time allows for correcting mistakes only because you remember what happened the "first time."
  • An interesting case in Second Sight. The protagonist, John Vattic finds himself in a hospital with no memories of his past. The memories come back steadily and he remembers them very vividly (to the point of passing out during the recalls). However, every time he remembers something, he finds that certain things in the present have changed. For example, he looks up the information on his possible Love Interest and finds out that she's dead. He then has another flashback (playable), in which he ends up saving her life. After snapping out of the flashback, he looks at the computer again and notes that she's now alive but in a mental institution. Close to the end of the game comes the twist: the past is actually the present, and the present is actually a possible future he's seeing using his latent Psychic Powers.
  • In Bioshock Infinite, people who are killed in one dimension retain their memory of being dead, which results in nose bleeds and insanity. Booker also retains his memory of being the hero of the Vox Rebellion as well as dying when he travels to a different dimension.
  • In Assassin's Creed III DLC "The Tyranny of King Washington," Connor retains his memory of the original timeline and is utterly stunned that so many of his Revolutionary allies have gone evil. His mother is surprised when he easily puts on his father's Assassin blades, as if he's done that a hundred times. Then it turns out that it was All Just a Dream induced by an Apple given to Washington showing both of them a possible future. Washington is horrified and asks Connor to put the Apple where no one will find it. He then grows determined to ensure that the new nation remains a republic.

    Web Comics 
  • Explicitly "explained" with the retroactive changes caused by the titular Misfile: Ash and Emily can remember their lives before reality was changed because their souls are unavailable to the filing system for updates, so their memories can't be altered by the filing system. The other main character in on the secret, Rumisiel, is an angel, and so is either not included in the filing system or is unaffected by changes to Earth's files.
    • Rumisiel may not be ripple proof; he only knew that he'd messed up a couple of files and roughly where to find his victims. His first guess on what he'd done to Ash was that he'd aged her into a teenager. It's possible that he was too high at the time to realize exactly what he'd done, and only figured it out once he was explicitly told.
  • In Breakpoint City, Ben wonders if this is possible when he realizes that he just accidentally gave someone the blueprints for his time machine, goes back to their apartment, and finds a construction zone in its place. If she altered the past enough that she no longer lives there, how can he remember meeting her there, since he wouldn't have met her there?
  • A great deal of the plot of the now-completed webcomic Narbonic is based on the time-travel adventure of Dave Davenport, and on the fact that afterwards he's the only one who remembers that he used to smoke.
    • Largely, this is an extremely long-term foreshadowing of events involved in the series finale. It's heavily implied that time travel can never really change history, but the astute reader will know this is untrue because of the smoking thing. Which happened years earlier in real world time.
  • This bites Zoe in the ass in Sluggy Freelance. She is downright pissed to discover that, thanks to the changes she made to the past, her history exam now includes an essay question on "The War of the Bug Squishers", a war Zoe helped start by going back in time, and consequently, doesn't know how it ended (or even that it's the same war she helped start).
  • Not involving actual time travel, but a teacher at the school The Good Witch is immune to the effects of the mass memory-altering spells that convince everyone else that the past happened differently.
  • Both played straight and double-subverted in Wapsi Square. Jin remembers every iteration of the Stable Time Loop the characters are meant to resolve, but isn't talking. Meanwhile, Brandi wrote a book in a previous iteration that explains step by step what to do, which is only accessible due to the existence of the Bibliothiki. The main character, however, is left completely in the dark until it's resolved.
  • For some unexplained reason, when history began to change in Ansem Retort, Riku had this. He managed to get Axel and Zexion to remember the proper timeline when he got them to remember that Andrew Jackson (who they fuse into) is on the twenty dollar bill, and not Jack Bauer.
  • In Schlock Mercenary, when Kevyn Andreyasn and a miniature version of Sergeant Schlock went back in time to prevent the Bad Future, Schlock accidentally merged with Future!Schlock and now has both sets of memories.
  • When a Hero of Time in Homestuck goes back in time to make a change to restore the alpha timeline, they remember the alternate timeline that they experienced. Also, when John becomes unstuck from canon and actually alters something we had already seen in the alpha timeline, Dave and Jade both have a feeling that the new way it happens isn't how it is supposed to go. Another version of John fixes things.

    Web Original 
  • Ben "Yahtzee" Croshaw's short story, Richard and Maureen's Amazing Time Travel Adventure plays with the trope. The main characters of the story are able to invent a time machine and make changes in the timeline merely by speculating about them. As they're doing this, their memories of how things used to be spontaneously vanish.
  • At the climax to Red vs. Blue's Blood Gulch Chronicles, Wyoming's time-resetting power resets his foes' memory, with the exception of Tucker, whose alien sword prevents the effect and lets him and Church beat Wyoming.

    Western Animation 
  • Justified in Code Lyoko, where the Return to the Past function doesn't affect the memories of anybody who has been scanned into the Supercomputer (as well as all the Supercomputer's programs — and incidentally XANA). However, they only travel to the past and see it as Mental Time Travel, which avoids some problems (most notably, they always remember both histories). In the prequel, this became a problem when Jeremie hadn't been scanned and thus didn't remember. Fortunately, he'd been playing with the supercomputer for long enough that he bought their story immediately.
  • Lampshaded in an episode of Static Shock: A new metahuman with time travel powers who goes by the name of Timezone appears and teams up with Static and Gear; they, along with Ebon, have a time travelling adventure, at the end of which Timezone goes back in time and prevents herself from ever getting powers. She ends up with no memory of the events, and as Richie explains, their adventure now never happened. When Virgil protests that he and Richie both remember the events, Richie advises him not to think too hard about it. This also handwaves the paradox of how she could've prevented herself from getting her powers without her powers.
  • American Dragon Jake Long lampshaded this in the last episode. Jake is talking about Rose, and Spud points out that Jake shouldn't even remember her because of how his wish altered reality. Jake presents a photo and Spud says that that shouldn't exist either.
  • Justice League
    • In "The Once and Future Thing", the League goes on a time-travelling adventure against Chronos; while several members travel around, only the two that are there when the reset happens remember it. And those two (one of whom is Batman) have to take a moment to recover from the mental whiplash of cutting instantly from a desperate chase through time to... sitting calmly at a cafeteria table, back where it all started.
    • Earlier, in "The Savage Time," a force field that Green Lantern was using to guide a spaceship in for a landing protects him and everyone in it from the effects of a timeline change.
  • Jackie Chan Adventures had an episode in which the Big Bad Shendu had used Jackie in a plot to rewrite the history of the world (in a literal, giant Book of History) that more or less canceled all of Shendu's defeats and favors the villains. While in the process of rewriting history, Jade rips a page off the book that mentions her place in history. She keeps this paper so when history is rewritten only she remembers how things were. In this alternative reality Shendu also remembers what things were like, so he is surprised when Jade is able to gather all the main characters to combat him. In the end, the good guys rewrite history to what things were originally like and only they remember this alternative reality.
    • All humans retain their original memories in that series when history is altered by time-travel even the ones who didn't travel. For example, when Jade accidentally went back to 1976, she prevented Jackie from gaining a scar. While it disappeared from Present Jackie's body, he still remembered it and that clued him to the place in time she went to. When Future Jade came to Present Time to destroy a set of magical teeth so they wouldn't be used to restore Shendu, Future Jackie and Future Uncle still remembered them being used in their time.
  • Averted in Kim Possible: A Sitch in Time, where nobody remembers the alternate timeline at the end… except Ron has a subconscious aversion to Norwegian meatcakes, and can't figure out why. Played straight earlier in the movie, where Ron is looking at yearbook pictures, and is confused when one of them changes.
  • In an episode of the Men In Black animated series, an enemy uses time travel to slowly reduce the MiB to a small backroom operation. Jay is the only one who notices the changes, as he had been previously affected by an alien device that made super-intelligent and immune to the ripple effect.
  • In Danny Phantom, Clockwork sets time back two hours before the Nasty Burger incident that would trigger the Bad Future so neither Danny's parents nor his teacher Lancer gained knowledge of their once imminent deaths and Danny's Secret Identity.
  • Averted in the South Park episode "Go God Go XII". Cartman calls his past self, causing several changes to the future world that Cartman apparently doesn't notice. But played straight later in the same episode when Cartman changes the past again and only remembers the old timeline.
  • In the episode of The Adventures of Sonic the Hedgehog where Robotnik, Scratch, Grounder, Sonic and Tails go back to an Ancient Egypt-like era, Scratch and Grounder make it so that two of Sonic's ancestors don't meet, resulting in Sonic not being born. But though Sonic disappears from existence, for plot convenience Tails is still there and remembers him, allowing him to set Sonic's ancestors back up.
  • In the Futurama episode "Time Keeps On Slippin'", Farnsworth using chronitons to age his atomic supermen from superbabies causes the universe to randomly skip forward in time. Everyone acts normally during the skips, only to suddenly get Laser-Guided Amnesia when time starts up again normally. Things get even more confusing when isolated areas begin skipping, which observing characters can see and comment upon.
  • After Johnny Test changed Porkbelly's history, he had to take a test about the city's history. He failed it because he remembered the original history and not the new history.
  • Dog City: Baron goes back to the time the pilgrims purchased the new world from the natives and made a better offer: squeak toys. This created a Bad Future where he rules. Somehow, Ace and Eddie had this and, after visiting a timeline where Eddie ruled, went back to the past and made an even better offer: a technologically advanced (even for present time standards) fire hydrant the heroes took from the Eddie-ruled timeline.
  • While not being a time travel example, in The Fairly OddParents, there are a lot of episodes where Timmy makes wishes that drastically alter the world, and all the characters in the episode act like the world has always been like this, except for Timmy and his fairies. Also, some episodes with time travel play this trope in its natural form.
  • The finale of Scooby-Doo! Mystery Incorporated. The protagonists remember the original timeline because of this; Harlan Ellison also remembers because of his inherent psychic abilities.
  • Star Trek: The Animated Series episode "Yesteryear". A trip back through the Guardian of Forever changed history by causing Spock to die as a child, before he entered Starfleet. Only the time travelers remembered the original timeline in which Spock existed.
  • Randy Cunningham: 9th Grade Ninja: When the Sorcerer's past was altered and his eight-century-long imprisonment erased, he still remembered it. Later, when Randy and the original Ninja imprisoned the Sorcerer back in the 13th century, Present-time Sorcerer didn't forget his brief freedom.

    Real Life 
  • This help wanted ad.
  • Stephen Hawking's time traveler party, as mentioned in Into the Universe. No one came... or did they? Maybe he's keeping mum.
  • A theory about the workings of our universe posits that unlike energy (and by extension mass), information can be created out of nothing and disappear into nothing. This might allow for Ripple-Effect Proof Memory, provided time travel is possible.
  • There is a slight lag with broadcasting in any live performance. This allows you to cut out segments that could be offensive to certain people (which carries with it some Paranoia Fuel about censoring unpopular ideas). The people with this therefore would likely be those who attended the live performance.


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