Ripple Effect Proof Memory - Television Tropes & Idioms

Obligatory Suzumiya Haruhi reference and an interesting example. Haruhi accidently sets the last two weeks of summer to repeat endlessly because she doesn't want it to end. Nobody has ripple proof memory and Suzumiya has the least ripple proof memory of all. The rest of the brigade do however, experience déjà vu at an increasing rate. They've gone through about 15 thousand repetitions, with realizations of what's going on increasing in frequency. Yuki, though, apparently exists partially outside time or something and remembers every... single... time. Yes, she is now subjectively several hundred years older or something close to that. Justified!
- And in "Disappearance", when Yuki reshapes the world, she makes it so Kyon has a Ripple Effect Proof Memory. Everyone else does not, however.
Deconstructed in Higurashi No Naku Koro Ni. It's in fact the main source of conflict during the second season.
Occurs in xxxHolic 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 all but a few people once her time starts moving again and she dies as she should have years before.
Pretty much all instances of Time Travel in Pokemon. 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.

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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.

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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 Astro City 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 Ripple Effect Proof Memory (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.
- Wait, wait, wait. Spidey has this? *Shoots a grunt in the head* YAY!!!!!!!!!
- Wolverine knowing is an interesting plot point. As it turns out, Scarlet Witch's rewrite gave everybody what they most wanted (Magneto rules a world were mutants are more and more common, Spidey's married to Gwen Stacy and his Uncle Ben's still alive, etc), but what Wolverine most wanted was to have an unaltered memory (as his past was lost to him from all the experiments done). So while everyone else is having their notion of reality screwed with, he actually ends up having his own history straight for the first time in his existence as a character. This carries over after everyone else has their memory restored- and naturally, given how he lost his memory, sparks a Roaring Rampage Of Revenge.
The late Bart Allen, the hero known as Impulse, Kid Flash II and (briefly) Flash IV, had a permanently Ripple Effect Proof Memory 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.
- It's speculated by some that Impulse's Ripple Effect Proof Memory is an effect of being a time anomaly himself; when he first arrived in the present, the timeline he was native to did not exist, and only came into being a few months later thanks to a Crisis Crossover.
Tom Strong featured a beautiful 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.

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Time Travel stories are rife in the world of Harry Potter fanfiction. One almost univeral 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.
- It should be noted that canonically this should not be possible. Based on the climax of Harry Potter and the Prisoner of Azkaban, the Potter Verse has an immutable timeline.
  - It's impossible given what is shown in the books, but not by what is referred to. Your past self committing suicide is supposed to be a danger of time-travel. If there was an immutable timeline, this would be impossible. Even if killing your future self is what's being referred to as suicide, nobody would go back in time after they killed someone who looked like them, so it wouldn't be a problem.
  - What if you went back in time to stop yourself from killing someone and only realized at the last second that the person you killed was yourself?

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Naturally, the Back to the Future trilogy.
- It is a bit strange to note, 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 literally 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.
- 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.
  - Which fails to explain where the OTHER Alternate 1985 Marty resulting from the events of the first film is...
  - Just because Biff sent Marty to boarding school, doesn't mean he's still there. He could be merging with or overwriting his clones.
- 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.
  - Of course, it could be something else than Ripple Effect Proof Memory. For Doc, (who's already Absent Minded), it HAS been 30 years since he last saw Marty in cowboy clothes (the 1955 to 1985 period and the period between him arriving in 1885 and Marty showing up). A more direct example of this is the following: 1985 Doc is sent in 1885. 1955 Doc learns that Bufford Tannen will kill his future self in 1885, and sends Marty back to 1885 to rescue 1985 Doc. 1985 Doc is however unaware of anything his 1955 version (which, again, represent his past self) knows by that point: he doesn't know Bufford's going to kill him, and he does not know Marty is about to show up to rescue him; despite his 1955 (past, yet located in the future) self being aware of both those facts.
- It's pretty much necessary that Marty's memory adjusts after the first movie, at least for there to be anything like a happy ending. Remembering a completely different life than what actually happened in the revised timeline would pretty much inevitably destroy his life.
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 physical 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 Jesus-like markings in the future, 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.
The movie 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.
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. Of course, 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 animated film 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.
In the Disney film Minutemen, the time travelers have this, but the people who asked them to change the past don't. Fortunately, the 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 Ripple Effect Proof Memory!
Godzilla vs. King Ghidorah, the only Godzilla movie so far to feature time travel, uses this trope. After the timeline has been altered in WWII 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 even 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...yet references to Ghidorah are made and Godzilla is still at the larger scale. Wall Banger alert!

Close Films

The third book in The Dark Tower series subverted this. Roland was going insane because he was remembering two timelines, one where Jake died, and one where he didn't. Of course, Jake was having an even worse time about it.
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 Lathe of Heaven, George Orr is the only one who knows reality has changed. Of course, 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).
Robert Silverberg's Up the Line discussed this and other temporal oddities fairly well.
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.
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.)
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.
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 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 literally 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!
This plays a big part of the plot of A Game of Universe, as the protagonist has no Ripple Effect Proof 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.
Time travel is used several times in Animorphs; one in particular has 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.
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 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.
In the concluding trilogy of the Sword of Truth sage, a magic spell called Chainfire erases Kahlan from the memory of everyone. Everyone except for Richard, of course (the Sword of Truth protected him).

Close Literature

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 devistating 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".
Journeyman
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?
  - Man, those things can do everything!
  - Donuts; is there anything they can't do?
  - 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 have Ripple Effect Proof Memory. Might be party due to the fact that 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.
- Star Trek The Animated Series with "Yesteryear", which also featured a trip back through the Guardian of Forever that changed history. Only the time travelers remembered the original timeline in which Spock existed.
- 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..
- In another episode of Deep Space Nine, Sisko and Dax 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.
- In Star Trek First Contact, the Enterprise becomes Ripple Effect Proof due to getting caught in the Borg ship's "temporal wake" before they followed it back through time.
- 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.
- 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.
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 programed to clean toilets, not explain things like DNA or time paradoxes. "In other words, I made a mistake. OK?!?"
In Primeval series 2, Nick and Helen Cutter are the only ones who can remember Claudia Brown.
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.
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.
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.
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 one episode of the revived Outer Limits, an already-unbalanced female 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, a female homicide detective uses the machine to go back and save the scientist from the sexual assault which originally caused her problems. 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 Its Good.
Angel, of the eponymous vampire-detective series, had an episode in which he dealt with the Oracles (Deus Ex Machina — almost literally — 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.
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 Ripple Effect Proof Memory, 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 by means not recalled by This Troper, 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 pretty much Everything-proof.

Close Live Action TV

Feng Shui's Innerwalkers have this by default. Once someone has been through the Netherworld, they're basically 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.
- It's notable that 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.
- Likewise, 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. Of course, given how duplicitous Time Lords and their politics can get, and how evil the Neverpeople are, how much we can trust what we're told is arguable.
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.

Close Tabletop Games

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.
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. An agent is constantly on duty at all times, and in the event of the detection of a "temporal rip" (the ripple effect), the agent will jump back to prehistoric times and reclaim a disc containing a complete history of the world. This keeps both the history and the agent from being altered by the rip, which travels only forward in time and won't affect anything not in the time periods it hits. Comparing the disc with a complete history of the post-rip world essentially shows the agent exactly what's been changed-thus forming the entire basis of the games.
- Only the first one, technically, although Ripple Effect Proof Memory 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.
Pokemon Mystery Dungeon. Question: if Insert Player Name Here never existed, then how does Insert Partner Name Here remember he/she even existed?
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. But that seems to be the exception in the game, not the rule.)
A weird related effect occurs in Mario And 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 Ripple Effect Proof Memory 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.) However, in one 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 as an improvement Max and Monica made in the future known timeline.

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Explicitly "explained" with the retroactive changes caused by the 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 are 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.
  - Of course, it's entirely 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.
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).

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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.

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In Code Lyoko, 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 incidently 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).
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.
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.
In Justice League Unlimited, 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.
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.
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 boiler 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.
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.

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JFK was supposed to live! I swear it!
- Wait... Are you saying he didn't?
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