History Main / ForgottenPhlebotinum

[[folder:Anime and Manga]]

* ''Manga/JoJosBizarreAdventure'': In [[Manga/BattleTendency Part 2]], it's shown that [[StupidJetpackHitler Nazi Germany had the technology to turn people into extremely powerful cyborgs]], even [[WeCanRebuildHim those who have suffered deadly wounds like being blown up by a grenade]]. This is rarely referenced afterward, save for two characters' mechanical hands. When one of those characters loses their legs, the idea of them ever being replaced with cybernetics is never brought up.

** In the first episode Sailor Moon's hairclip things (on her odango/buns) can magically allow her to hear people in distress. This comes in handy, as she hears her best friend [[WeirdnessMagnet Naru]] being attacked by the MonsterOfTheWeek and goes to save her. This power is never shown again in later episodes, even though it would probably have come in handy. Similarly, in the first chapter of the [[Manga/SailorMoon manga]], the costume included a mask in which she could see the monster attacking Naru by looking in the goggles. The goggles were quickly phased out in the manga, last seen in one transformation sequence where Usagi discarded them as she transformed, though why this happened was never explained. Considering that the monsters of the week/chapter were usually close by anyway, this power wasn't really that necessary in retrospect...

* In ''Anime/SuperDimensionFortressMacross'', we see that the HumongousMecha piloted by humans have head-mounted cannons - that got used exactly four times during the ''entire show''. Only twice as a weapon - both of the other times they were used as ''cutting tools''.
** Thankfully, the head cannons see more consistent use in later ''Anime/{{Macross}}'' series.

* Franchise/{{Superman}}:

* ''Series/BlakesSeven''.

** The TARDIS has had many features used over the decades that were completely forgotten soon afterwards: it can drift back to its owner if separated from them in time ([[Recap/DoctorWhoS12E5RevengeOfTheCybermen "Revenge of the Cybermen"]]), it has a Space-Time Visualiser ([[Recap/DoctorWhoS2E7TheSpaceMuseum "The Space Museum"]], [[Recap/DoctorWhoS2E8TheChase "The Chase"]] and [[Recap/DoctorWhoS4E6TheMoonbase "The Moonbase"]]), a Hostile Action Displacement System ([[Recap/DoctorWhoS6E4TheKrotons "The Krotons"]], [[Recap/DoctorWhoS33E8ColdWar "Cold War"]]) and other features. Considering that the TARDIS was a museum piece even before the Doctor stole it over a millennium ago and is highly temperamental even at the best of times, it's entirely probable that these things literally don't work anymore.

** [[Recap/DoctorWhoS13E3PyramidsOfMars "Pyramids of Mars"]]: The Doctor says the TARDIS' controls are isomorphic, meaning only he can operate it, which keeps Sutekh from having him killed. Given the number of times others have operated the TARDIS, this was either another lie or a security setting.
** In [[Recap/DoctorWhoS14E2TheHandOfFear "The Hand of Fear"]], the Fourth Doctor states that the TARDIS' temporal grace disallows violence within the TARDIS. Subsequently (and previous) stories ignored this. The Eleventh Doctor [[Recap/DoctorWhoS32E8LetsKillHitler later admitted]] that it was a "clever lie".
** The Chula, mentioned in [[Recap/DoctorWhoS27E9TheEmptyChild "The Empty Child"]]/[[Recap/DoctorWhoS27E10TheDoctorDances "The Doctor Dances"]], [[spoiler:produced nanobots capable of healing any injury and even reviving the dead, and in enough numbers to work over whole planets worth of people.]] Why hasn't the Doctor simply gone to Chula and got some for himself? One possible justification is that the Chula are implied to be [[ProudWarriorRaceGuy warriors]], with Jack's ship and the pod containing the nanogenes being a stolen Chula warship and ambulance for patching up their soldiers, respectively. Such a trip might not only be too dangerous, but the Chula might not ''want'' to share this technology with anyone.
** At the end of [[Recap/DoctorWho2005CSTheChristmasInvasion "The Christmas Invasion"]] [[spoiler:the vast alien starship that had been menacing the whole planet is utterly destroyed by a colossal laser fired from beneath London. This fantastic weapon devised by Torchwood London from captured alien technology for the defense of the kingdom from extraterrestrial perils is never again mentioned, despite London being menaced by aliens so frequently that its citizens get into the habit of evacuating over Christmas so as not to be there when the monsters turn up]]. However, [[spoiler:the same technology (or, at least, similar special effects) seems to now be incorporated into the ''Valiant'', as seen in [[Recap/DoctorWhoS30E5ThePoisonSky "The Poison Sky"]], so even if the main weapon was destroyed, it's not all gone to waste. At least, until [[Recap/DoctorWhoS30E12TheStolenEarth "The Stolen Earth"]], when spoiler:the ''Valiant'' is overwhelmed and destroyed by the Daleks off-screen]].
** At the end of [[Recap/DoctorWhoS30E1PartnersInCrime "Partners in Crime"]], the Doctor discards into a rubbish bin a sonic pen which opened a deadlock seal when used with his own screwdriver, one of the few locks his sonic screwdriver can't deal with.[[note]]Justified since the deadlock seal in question belonged to the pen's owner, so that was probably the ''only'' deadlock seal that the pen could open.[[/note]]
** [[Recap/DoctorWhoS38E3Orphan55 "Orphan 55"]] has an inexplicable absence of the TARDIS' TranslatorMicrobes when Graham and Yaz are unable to read a sign written in [[spoiler:Cyrillic]], requiring the Doctor to translate for them — even though the translation has worked on both writing and [[spoiler:Russian]] before. The only even slightly plausible explanation, not counting NegativeContinuity, is that the team's current distance from the TARDIS (since they were teleported directly to the planet the episode is set on) made it impossible, but the fact that everyone else at Tranquillity Spa thus apparently speaks 21st century English puts a big hole in this theory.

* The [[WaveMotionGun Phase Transit Cannon]] from ''Wing Commander II'' is never mentioned again outside of a brief note in the manual for the ''Kilrathi Saga'' compilation mentioning that it was discontinued due to technical problems, and the [[KillItWithFire flash-packs]] from ''Wing Commander IV'' isn't mentioned anywhere at all in later ''VideoGame/WingCommander'' games, as if the tech has vanished.

[[folder:Webcomics]]

* ''WesternAnimation/HeManAndTheMastersOfTheUniverse'': Skeletor had robot knights that he used as foot soldiers alongside his Evil Warriors. After a while, he stopped using them.

* ''WesternAnimation/AvatarTheLastAirbender'': Events surrounding the second season finale left many [[http://mad-sniper.deviantart.com/art/Forget-Something-43181126 wondering]] why Katara, who had theorized that her [[ChekhovsGun vial of water from the sacred oasis]] retained healing properties, didn't make so much as an attempt to whip it out and use on the mortally wounded TragicHero Jet a few episodes beforehand. [[WordOfGod The DVD commentary]] has the co-creators admit that they forgot it, [[HandWave but said]] [[HoldingBackThePhlebotinum it wouldn't have worked anyway]]. In universe, it could be written off as Katara saving the water in case Aang had become mortally wounded, especially since Jett's wound was internal.

*** In an example which works in reverse, in [[Recap/StarTrekS1E25TheDevilInTheDark The Devil In The Dark]], [=McCoy=] uses a silicon-based cement to heal the Horta, said to be used to build emergency shelters. Too bad they didn't bother to beam any of that stuff down to Sulu and company as they froze on the surface of the planet in [[Recap/StarTrekS1E5TheEnemyWithin The Enemy Within]]

*** The Rainbow of Light is introduced in ''WesternAnimation/MyLittlePonyRescueAtMidnightCastle'' as a powerful FantasticNuke and said to be one of the most powerful magic artifacts in Ponyland. The number of times it's used can be counted on one hand; against Tirek, against Catrina, against the Witches of the Volcano of Gloom and the Smooze, and to clear away rain clouds so they can pick cherries. After that, it's never seen nor mentioned again, save for once when Megan remembers they have it and plans to use it, only to drop it where she can't get it back and has it returned to her after the threat has been defeated.

* As pointed out in ''[[WebVideo/YuGiOhTheAbridgedSeries Yu-Gi-Oh!: The Abridged Movie]]'', Kaiba never used the cards given to him by Pegasus ever again, even in episodes set later, and though they are able to defeat the Egyptian God Cards. Nor does anyone in the series ever mention either the Pyramid of Light or the Blue-Eyes Shining Dragon. Ever. (Granted, the movie wasn't part of the original storyline, neither anime or manga.)

This trope does not necessarily denote bad writing. It can be (as noted in the ''[[Webcomic/TheOrderOfTheStick Order of the Stick]]'' example) essential to the story. If the protagonists have some piece of phlebotinum that makes them nearly or actually invincible, [[DramaPreservingHandicap many plots have to be thrown out the window.]] Some would call this unwillingness to [[StatusQuoIsGod change the Status Quo]] and then adapt to the new order of things "lazy", but when one is working on a regular series, changing the status quo, interesting though it can be dramatically, is not something to be done lightly. When it's a SharedUniverse this is even more the case.

Creator/LarryNiven is scornful of this trope, and coined Niven's Law, which states that once a technology or discovery has been introduced into a fictional setting, it must continue to exist in all chronologically later stories in that setting. The secret may be lost for a variety of reasons — society enters a dark age, the discoverer deliberately covers it up, or there really were NoPlansNoPrototypeNoBackup — but Niven would maintain that this smacks of lazy writing. At the very least, the precedent that such a machine is ''physically possible'' in the setting must be maintained, which would make it likely that older, HigherTechSpecies will possess it even if it never became prevalent in the protagonists' society.

Note that this trope is for powers or devices that are forgotten in general. Something which the character does use a lot and only is forgotten this one time is an example of ForgotAboutHisPowers. If it is remembered, but there's some excuse as to why it isn't used or won't work again, that's HoldingBackThePhlebotinum or ItOnlyWorksOnce. If they acknowledge it but don't have it on their persons, it's WeHaveForgottenThePhlebotinum. If they (finally!) remember to use it in the end, it's a ForgottenSuperweapon. When it's ''not'' forgotten and ''is'' used in a later episode because a writer wants to [[ContinuityNod acknowledge continuity]], it is ChekhovsBoomerang. Compare also with NeverRecycleYourSchemes in the case of villains. If it hasn't necessarily been forgotten but can no longer be used on a grand scale for whatever reason, see TechnologyErasureEvent.

Note that this trope is for powers or devices that are forgotten in general. Something which the character does use a lot and only is forgotten this one time is an example of ForgotAboutHisPowers. If it is remembered, but there's some excuse as to why it isn't used or won't work again, that's HoldingBackThePhlebotinum or ItOnlyWorksOnce. If they acknowledge it but don't have it on their persons, it's WeHaveForgottenThePhlebotinum. If they (finally!) remember to use it in the end, it's a ForgottenSuperweapon. When it's ''not'' forgotten and ''is'' used in a later episode because a writer wants to [[ContinuityNod acknowledge continuity]], it is ChekhovsBoomerang. If it hasn't necessarily been forgotten but can no longer be used on a grand scale for whatever reason, see TechnologyErasureEvent. Compare also with NeverRecycleYourSchemes in the case of villains.

Note that this trope is for powers or devices that are forgotten in general. Something which the character does use a lot and only is forgotten this one time is an example of ForgotAboutHisPowers. If it is remembered, but there's some excuse as to why it isn't used or won't work again, that's HoldingBackThePhlebotinum or ItOnlyWorksOnce. If they acknowledge it but don't have it on their persons, it's WeHaveForgottenThePhlebotinum. If they (finally!) remember to use it in the end, it's a ForgottenSuperweapon. When it's ''not'' forgotten and ''is'' used in a later episode because a writer wants to [[ContinuityNod acknowledge continuity]], it is ChekhovsBoomerang. Compare also with NeverRecycleYourSchemes in the case of villains.

** In ''Film/StarTrek2009'', the Spock from an alternate future introduces "transwarp transporting", which works across interstellar distances. He shows this to the younger version of Scotty, and uses it to send him and Kirk to the ''Enterprise'', which is currently traveling at warp speed. In ''Film/StarTrekIntoDarkness'', Harrison uses it to beam from Earth to the Klingon homeworld Qo'noS. This demonstrates that knowledge of the technology ''did'' leak out, but is now exclusively used by the villains, with the heroes seemingly no longer remembering how to do it, even though they were the first to learn how it works. Of course, it turns out [[spoiler:Harrison was on a top-secret Starfleet weapons development project, which implies the good guys are studying it, just ''quietly''.]]
** ''Film/StarTrekIntoDarkness'': It is revealed late in the film that [[spoiler: an augment's blood can resurrect the dead]], and is subsequently used to heal [[spoiler:Kirk from fatal radiation poisoning (after a point in which everything but his higher brain functions have failed)]]. This is a pretty significant discovery to have lost for two hundred years. [[spoiler:At the end of the movie, Starfleet just refreezes Harrison/Khan and locks him and the other augments away. Presumably they want to avoid any more disasters like, oh, ''the plot of the movie'', whose climax makes 9/11 look like a toy plane crash.]]

** In ''Film/IronMan1'', Tony Stark uses a small missile to easily obliterate the military tank that has just knocked him out of the sky. A small magazine of these would be incredibly useful in many situations in future movies, but apparently, he forgets to include more than one per suit. He does use a bunch of micro-missiles in later films, and eventually the nanotech armor means he can ''make'' missiles.
** In ''Film/AvengersAgeOfUltron'', Helen Cho has built a "regeneration cradle" that can heal grievous injuries by creating synthetic tissue and bonding it to the victim's cells. Apparently, nobody thought to use this on [[spoiler: Comicbook/WarMachine]] after a serious fall cost him the use of his legs in ''Film/CaptainAmericaCivilWar''. Heck, the movie even has a scene where doctors are shown examining him after the accident, and Helen isn't even ''mentioned''. Justifiable, considering that [[spoiler:there seems to only be one cradle, which was severely damaged in ''Ultron'', when Vision awakened and exploded out of it violently enough to knock Thor across the room]].

* ''Franchise/StarWars'': In the epilogue of ''Film/TheEmpireStrikesBack'', Luke Skywalker gets a like-OEM [[ArtificialLimbs prosthetic hand]] installed to replace the one Darth Vader removed in their duel. This is apparently the level of medical care that is available to plucky ragtag rebel groups within a week of the Galactic Empire kicking their asses at Hoth. Which has the effect of making Padmé Amidala's prophesied DeathByChildbirth in ''Film/RevengeOfTheSith'' as motivation for Anakin seem like she never visited a doctor the entire time she was pregnant: by precedent it would be surprising if anybody in her social class ever even had a bad cold that century. (Her actual death is marginally more justifiable considering [[spoiler:she was {{Force choke}}d by Anakin/Vader beforehand]].)

* ''WesternAnimation/FamilyGuy'': "[[Recap/FamilyGuyS4E3BlindAmbition Blind Ambition]]" has Peter go blind, and ends with him [[StatusQuoIsGod back to normal]] thanks to an eye transplant. Fast forward to "[[FamilyGuyS20E1LASIKInstinct LASIK Instinct]]", where Lois goes blind from botched LASIK surgery. Peter mentions his own brush with blindness in the former episode, but no one mentions the eye transplant. Fortunately, her eyes end up healing on their own.

* ''VideoGame/Borderlands2'' has a standard-fare New-U ([[TradeSnark TM]]) Respawn system. For the most part, it's [[GameplayAndStorySegregation ignored]]; all characters are [[KilledOffForReal killed off for real]] within the game's plot... with the sole exception of the "[[ExactlyWhatItSaysOnTheTin Kill Yourself]]" sidequest, in which the player must use the New-U to collect their reward. The game's developers regretted this so much that DLC New-U machines would sometimes say "This respawn is not canon" when resurrecting the player.

Note that this trope is for powers or devices that are forgotten in general. Something which the character does use a lot and only is forgotten this one time is an example of ForgotAboutHisPowers. If the device is remembered, but there's some contrived excuse as to why it isn't available or won't work, that's HoldingBackThePhlebotinum or ItOnlyWorksOnce. Not to be confused with WeHaveForgottenThePhlebotinum. If they (finally!) remember to use it in the end, it's a ForgottenSuperweapon. When it's ''not'' forgotten and ''is'' used in a later episode because a writer wants to [[ContinuityNod acknowledge continuity]], it is ChekhovsBoomerang. Compare also with NeverRecycleYourSchemes in the case of villains.

* The mortar used for the Great Wall of China - which has lasted for hundreds of years - also used to fall into this trope [[spoiler: until recently, when scientists discovered that the secret was...sticky rice!]]

** In the fifth episode, Protect the Pure Heart! A Three-Way Battle, Ami uses her mini supercomputer to track Unazuki's Pure Heart Crystal after it had been stolen from her. Ami doesn't use her supercomputer again in this season, in spite of how useful it could have been in tracking the Talismans.
** In one episode, Rei divines using the Sacred Fire to try to uncover the answer behind her strange premonitions. Why she couldn't have done this to find out more about the Talismans is never stated.
** After Chibi-Usa's Pure Heart Crystal is stolen by a possessed Hotaru, the evil entity controlling her was revealed to be Mistress 9, not Sailor Saturn, and the other Senshi realize that Hotaru had been possessed by a Daimon the whole time. It would have been logical for Sailor Moon to use the Silver Crystal to free Hotaru from Mistress 9's possession, as she had used it in the previous seasons to return the carriers of the Rainbow Crystals to their human forms, freed Mamoru from Metallia's control, purge the evil from the Spectre Sisters and turn them into normal humans, and purged the evil from Black Lady and turned her back into Chibi-Usa. Purging evil from a person or place has been a power of Sailor Moon's since the beginning and it's a power that doesn't drain her of her energy, so it would stand to reason that this would be able to save the world and defeat the enemy without sacrificing Hotaru. Instead, the Silver Crystal isn't even mentioned as a possible option in defeating the Death Busters or saving Hotaru, with its last mention being the second episode of the season where Usagi worried it had lost its power after her transformation came undone. It was revitalized by her and Mamoru's love and allowed her to transform again after her brooch became the Cosmic Heart Compact, but it's never mentioned for the healing powers it is known for, resulting in a lasting dilemma over whether Hotaru can be saved or not.

* ''Manga/JoJosBizarreAdventure'':
** The first two parts focused on protagonists using [[PowerOfTheSun the Ripple]] in [[SwissArmySuperpower a wide variety of ways]] to fight vampires and similar creatures. From part three onward, the series focuses instead on [[FightingSpirit Stand]]-based duels, no new Ripple users are introduced, and the one Ripple-user that's still around only uses its [[ThisLooksLikeAJobForAquaman now-highly situational]] vampire-slaying ability.
** Cyborgs were introduced in Part 2 and are rarely referenced afterward, save for two characters' mechanical hands. When one of those characters loses their legs, the idea of them ever being replaced with cybernetics is never brought up.

** A segment of a season 3 episode opens with Icy boasting about a new fire power Valtor gave her. In the Trix's battles against the Winx, including the one just a few minutes later, she doesn't use it (and in fact, it's ''Darcy'' who sets a library on fire in a later episode, not Icy). And during the battle in the same episode, Layla sneaks up behind Darcy and Stormy to tie them up, even though way back in the second ever episode, she sensed Bloom's presence behind a garbage can, even though Bloom was well out of her view. (However, the [=non-4K=] version does mitigate the stupidity in both cases somewhat.)
** The Trix only used their fusion powers once to fight Lord Darkar, and never again after it, despite the fact that such a power could have been useful in any one on one fight.
** A season 1 episode saw Icy destroy Red Fountain by freezing it with a nifty ice dragon. Season finale, Icy doesn't even make any effort to use it to freeze Alfea, or to take on Bloom, who has an fire-energy dragon of her own.
** Bloom was shown to be able to use her powers to revive the dead. It's not explained why [[spoiler:Nabu]] is still dead. This was changed to breaking a sleeping spell in the 4kids version, which removes the contention entirely.
** In early season 3 there's nothing stopping a blind Layla from waiting to use Queen Ligea's healing staff the next sunset after she uses it on its owner. However, Faragonda gets around this by revealing she has Fairy Dust.
** The Charmix from season 2. Sure, it was SoLastSeason, but there's nothing else preventing the fairies who hadn't earned their Enchantix from using it in season 3, especially like when they're battling the Trix. Yet the only time it's even mentioned in season 3 is when the school headmistress talks about Enchantix.
** In the 21st episode of the third season, Nabu claimed that the reason he had stowed away on the Specialists ship was so he could practice his invisibility spells against monsters living in the area the Winx were travelling to. Nabu's ability to turn invisible hasn't been seen again since this episode. (Although it's possible that he used this ability off-screen during season 4's episode 20 when he went to the nature fairy Diana's castle to try to save the Specialists, but this is just a theory...)