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A TimeTravel trope, Retroactive Preparation is a twist on the YouAlreadyChangedThePast plot where the existence of a StableTimeLoop works to the advantage of the character's goals rather than thwarting them.

Let's say your favorite show is about to air, but you forgot to program your [[TechnologyMarchesOn VCR or DVR]] to record it. You run up to your front door, discover it locked, and realize you don't have your keys. What do you do? Break a window? Bust down the door? Drop down the chimney? Watch it at a neighbor's house? Hurry! There's less than a minute left! Oh, if only you'd thought to leave a key hidden under the doormat or something!

But wait! You have the next best thing: A time machine!

Secure in that knowledge, you look under the doormat and discover the key -- it's been left there for you by your future self. Thanks to future-you, you've been prepared the entire time.

If you have a time machine, then no matter what hurdle is set before you, you have all the time in the world to prepare for it ''after'' you've already overcome it, even if you are running on SanDimasTime. This rule mainly applies when the situation can be solved by having the right equipment at the right time, and the people in said situation are aware of the StableTimeLoop. It's like being CrazyPrepared, minus the foresight. After you "discover" your key and watch your show, you just make sure to use the time machine and put the key under the doormat for your past self.

Of course, there's no need to actually show anyone setting it up, just the end results.

If it ''is'' shown getting set up, sometimes a very strange thing will happen: The time traveler might end up rigging both the way past and original obstacle. E.g., when you're putting the key in place, you discover the door was left unlocked, and you know it 'was' locked, so you lock it.

Compare TrickedOutTime, the circumvention of the StableTimeLoop, and contrast YouAlreadyChangedThePast, the failed attempt to SetRightWhatOnceWentWrong. See also TemporalParadox.

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!!Examples

[[folder:Anime and Manga]]
* In ''[[LightNovel/HaruhiSuzumiya The Disappearance of Haruhi Suzumiya]]'', Kyon [[spoiler: mobilizes the SOS-dan to come back in time and save himself from Asakura and fix the whole parallel universe thing.]]
* ''Manga/{{Bleach}}'': Fullbringers manipulate souls, and according to them all matter has souls. [[spoiler:Tsukushima's special power allows him to become a [[SelfInsertFic self-insert character]] in anyone's lives by stabbing them, retroactively becoming their friend, lover, commander, etc. Then he reveals that he can do this to ''any inorganic matter'' by retroactively preparing a trap for his opponent, Byakuya. Oh, and BTW? He's seen all his moves too.]]
* ''Anime/PuellaMagiMadokaMagica'' has [[spoiler: Homura]], who combines her [[ResetButton time]] [[GroundhogDayLoop powers]] to try and [[spoiler: save Madoka]]. At this point, she's basically running a NewGamePlus with all the [[HyperspaceArsenal weapons]] and experience she's gained.
** She's also the [[Pantheon/TimeAndSpace current Trope Goddess.]]

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[[folder:ComicBooks]]
* A variation occurs in ''[[ComicBook/SupermanAndBatmanGenerations Superman and Batman Generations III]]'': [[spoiler:{{Darkseid}}'s plan to conquer Earth starts by sending an invasion fleet to attack the planet. Should they fail, the survivors time travel back 100 years and try again, and so on and so forth.]]
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[[folder:Fanfiction]]
* In ''Fanfic/KyonBigDamnHero'', Kyon has to travel several days back to prepare countermeasures when [[spoiler:Sasaki is kidnapped]].
** At one point the SOS Brigade is in an urgent need of a dimensional anchor. Immediately after Kyon realizes one may be in Tsuruya's possession there's a knock on the door: Tsuruya just arrived to the clubroom to deliver the dimensional anchor, as per requested by Kyon('s future self).
%%* ''FanFic/HarryPotterAndTheMethodsOfRationality'' plays {{Xanatos Speed Chess}} with this trope.
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[[folder:Films]]
* Not only is it used in ''[[BillAndTedsExcellentAdventure Bill & Ted's Excellent Adventure]]'', it's practically elevated to a martial art in ''Bill & Ted's Bogus Journey'', where the climax has both the titular heroes and their nemesis making use of this trope [[spoiler: before pointing out that only the ''winner'' of the showdown can actually make use of it]].
* In ''Film/{{Paycheck}}'', Ben Affleck's character does this not by going back in time, but by seeing the future before being stricken with amnesia.
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[[folder:Literature]]
* In ''Literature/ArtemisFowl: The Time Paradox'', Artemis and Holly use this once to get out of trouble, but a second attempt falls flat.
* This is the premise of Creator/PhilipKDick's short story "Paycheck".
* Creator/JackMcDevitt's novel ''Time Travelers Never Die'' makes extensive use of this principle.
** So does ''The Man Who Folded Himself'' by David Gerrold, the time traveler using it even to get "immortal".
* {{Subverted|Trope}} in ''Literature/TheRiftwarCycle'' where Pug sometimes receive instructions apparently written by himself in the future. They are actually written by the god Kalkin.
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[[folder:Live Action TV]]
* ''Series/DoctorWho'':
** Because of this rule, The Doctor was able to save River Song in "Forest of the Dead".
** This is also the Doctor's only recourse in "Blink", not so much helping himself as helping Sally Sparrow defeat the Weeping Angels in 2007 because they sent him back to the 1960s without the TARDIS.
** Parodied in the non-canonical ''The Curse of Fatal Death'', where both the Doctor and the Master attempt this. Repeatedly.
** Used in the Series 5 finale "The Big Bang", repeatedly, where we first see the Doctor show up and give random orders, leave, come back a second later, give more, and repeat a few times. Later, we see it from the other side, and learn he's doing this in real time in the future as he figures out what he needed to have already have happened. Thanks to the TimeyWimeyBall in that universe, he probably can't rely on things he's going to do later, so going back and retroactively doing them the instant before he needs them is safer.
*** Rather cleverly at the very end, we find out that two events earlier in the series that didn't make much sense at the time (the TARDIS returning to young Amy waiting on the Doctor, despite us knowing that she didn't see him again till twelve years later; and the Doctor telling Amy to 'remember what I told you when you were seven') turn out to be future versions of the Doctor, setting things up so Amy will remember him. [[spoiler:Well, actually, it's the Doctor reversing through his own timeline as he gets erased from time, so he's really just taking advantage of involuntary time travel rather than having planned it, but it works the same way.]]
** Straight-up depended upon by the Doctor in [[Recap/DoctorWho2011RedNoseDaySpecialSpaceAndTime the Red Nose Day special "Space"]]:
--> '''Amy:''' You don't know [[ContextSensitiveButton which lever]]?
-->'''Doctor:''' No, but I'm about to find out.
--> ''He gestures dramatically towards a door from which a future Doctor immediately enters the scene.''
--> '''Future Doctor:''' The [[InherentlyFunnyWords wibbly]] [[TechnoBabble lever]]!
** Taken to ridiculous levels in "The Day of the Doctor" where the Doctor pulls off a thousand-year preparation in order to [[spoiler:save Gallifrey by placing it in a time lock]].
* ''Series/StargateSG1'' two-part episode "Moebius" may not be a straight example, but it probably felt like that to the characters. In the beginning, they need a Zero-Point Module, decide to go back in time to when there was one on Earth, then hide it in a recently-discovered excavation site. At the end, General O'Neill finds himself watching a video of himself and his team explaining how and why they went back in time, which was recently discovered at an excavation site alongside the Zero-Point Module they needed. The only part O'Neill understands is that he doesn't have to do anything now that someone from another timeline did it for him.
-->'''Jack O'Neill:''' So... we don't have to go back in time and get the ZPM because... we already went back in time and got the ZPM?\\
'''Sam Carter:''' ... Pretty much.\\
'''Jack O'Neill:''' ... Alright then, let's go fishing.
** The movie ''[[Film/StargateContinuum Continuum]]'' brings up the question: what if both sides have time travel technology? Ba'al attempts to use this rule, but is defeated when Mitchell travels back even further and stops him in the past. Confused yet?
** The ''Series/StargateAtlantis'' crew probably wouldn't have survived the first episode if it weren't for the efforts of an alternate Dr. Weir and this trope.
* Averted in ''Series/SevenDays'', when the Russians manage to get their time travel technology off the ground thanks to Olga. Unfortunately, the technology is controlled by a rogue Russian general who proceeds to kill the Russian president and take power, intending to use the Sphere to prevent any attempts to remove him from power. Parker manages to "backstep" and stop the Russian program before their first jump. Interestingly, Olga previously worked on another Russian time travel program, which did not bear fruit but got her recruited into the Backstep program.
* ''Series/KamenRiderDouble'' has an odd variation on this. The Yesterday Dopant has the power to make someone do whatever they were doing [[ExactlyWhatItSaysOnTheTin exactly 24 hours ago]]. When Double shows up to fight it, Yesterday specifically baits him into actions that, when affected by Yesterday's power the next day, will cause him to try and assassinate a public figure.
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[[folder:Tabletop Games]]
* In the time-traveling RPG ''TabletopGame/{{Continuum}}'', this is called "slipshanking," and it's a viable alternative to [[HelpYourselfInTheFuture your future self actually showing]] up to help you out of a jam (a "Gemini"). Contrary to the Bill & Ted example, the game's rules insist that the player arrange the slipshank in-game, or take a Frag penalty. Too much slipshanking is a sign of poor planning, and a rude imposition on your future self who has other things to do.
* This is one of the bonus options in ''[[http://dig1000holes.wordpress.com/time-temp/ Time and Temp]]'' after you've gathered enough knowledge to come up with a good plan (represented by writing your die rolls into a grid and creating certain patterns).
* A card in ''TabletopGame/{{Chrononauts}}'' is called "Memo from Your Future Self". it effectively works like this, instantly negating the last card another player played. The German Chocolate Cake artifact can also be used as a Memo and the image on the card shows it having a postcard attached. (WordofGod [[http://www.wunderland.com/LooneyLabs/Chrononauts/Mysteries.html#1.1 says]] that it is not the postcard but the cake itself, and that the cake is just so good that it distracts the other player from [[TimeTravelTenseTrouble doing what they just did]]. Presumably the postcard is just to tell yourself when to use it.)
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[[folder:Video Games]]
* ''VideoGame/TimeSplitters: Future Perfect'' had numerous examples of this. One of the earliest examples is also one of the most memorable - you are given a key by your future self that you need to progress, and later pass the key on to your past self, [[TemporalParadox leaving its initial existence unexplained]]. FridgeLogic also sets in when you consider the fact that ''one'' key is being infinitely passed from Cortez to Cortez, meaning it'll probably wear down and break at some point.
* In ''{{Achron}}'' this is a very basic tactic. If your base is attacked, you can go back and build defenses in preparation.
* Subverted in ''{{Singularity}}'', where the player receives advice from the future in the form of time-reversed chalk marks on the walls. You'd think that would be a huge help, but they wind up not helping because whoever wrote them has/will-have-gone completely bonkers from excessive time travel and can't explain anything coherently enough for the messages to be helpful at the time you receive them.
* The Francise/KingdomHearts series is the result of the BigBad Xehanort doing this to himself. He uses his past self in his schemes to get the X-Blade, thus planting a seed of darkness in his past self's heart, which acts as a catalyst to eventually corrupt him into the monster that he becomes, [[StableTimeLoop who eventually uses his past self in his schemes...]]
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[[folder:Webcomics]]
* ''IrregularWebcomic'' [[http://www.irregularwebcomic.net/2367.html accomplishes this]] and ensures a StableTimeLoop at the same time.
* Thomas Overbeck's ''Webcomic/TimesLikeThis'', a webcomic focused on time travel, makes an art out of this.
* {{Homestuck}}: {{Stable Time Loop}}s are everywhere in this series, and there are devices that can send anything to any point in time as well as devices that can pull anything from any point in time as long as no paradoxes are created. The best example is the Bunny - [[ZigZaggedTrope although it also helps cause the problems it was created to solve]].
** A more subtle example: The trolls have the ability to contact anyone at any point in their timeline - up until a TimeCrash event. That TimeCrash event turns out to be important, so they eventually help the human characters create the event by telling them what they do in the future and passing on information from their future selves. This eventually leads the humans to do those things and pass on that information to the trolls.
** Lord English is a time-traveling demon who can only enter a universe once it has died. Once he enters, he can travel back in time and prepare his own summoning.
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[[folder:Web Original]]
* The OldeEnglish sketch "Pizza Delivery" parodies this in a RunningGag whereby all the preparation is for the sake of, well, pizza delivery.
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[[folder:Western Animation]]
* This trope sets the plot in motion in the ''WesternAnimation/{{Futurama}}'' movie ''Bender's Big Score''.
* In the ''KimPossible'' movie "A Sitch in Time", [[spoiler:Shego]] used the time monkey idol to change a whole lot of things, including making tons of money by buying a big company before the bubble burst, [[TimeyWimeyBall causing Ron to move to Norway]], [[TakeOverTheWorld Taking Over The World]] by mind probing the entire population, [[TimeyWimeyBall and travelling back to the future!past to tell her past self to steal the Time Monkey Idol]].
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[[folder:Real Life]]
* This is what Catholics believe [[TimeTravelTenseTrouble has happened]] when they pray for the souls of the dead. {{God}} hears their request in the present, but since He is eternal[[note]]'Eternal' in this case is a specific theological term meaning 'existing and acting in all points of time as if they were the present', rather than the common usage meaning 'endless'[[/note]], He works in the past to convince the person who [[TimeTravelTenseTrouble will be]] prayed for to repent.
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