A plot element that doesn’t get fully developed, perhaps on the assumption that they’ll have the sequel to take care of it. The element can be a relationship, a theme, or a character that clearly has a lot more possible development, but doesn’t get it. The central plot is no less complete and these aspects may have just been there to enlarge the universe, but they're there and available for later use -- more story to tell later. This can backfire if the sequel doesn't get made.

Compare SequelHook, which only occurs at the end of the story and is specifically geared toward inviting a sequel, DevelopmentGag, where hints of certain pathways the story could have taken are left as tidbits, and RefittedForSequel, where an element is ''dropped'' from the original production only to be modified to fit a later work.

The mouse in WhatHappenedToTheMouse can seem like one of these, but unlike a mouse, something that has been saved didn't disappear, it just wasn't resolved-- it is still present.

When this happens excessively, this will develop into a KudzuPlot.



[[folder:Anime & Manga]]
* ''Manga/{{Arachnid}}'' gets an ending with little closure for the heroine and several loose ends, but years later the sidestory ''Caterpillar'' became a POVSequel after its prequel arc.
* Reinforce Zwei of the ''Franchise/LyricalNanoha'' series. During ''[[Anime/MagicalGirlLyricalNanohaAs A's]]'' she was the very definition of LastEpisodeNewCharacter; she only had a single line at the very end of the last episode of the season. Come ''[[Anime/MagicalGirlLyricalNanohaStrikers StrikerS]]'' onward however she gets considerably more characterization and screen time.
* Nagisa Momoe, [[spoiler: the MagicalGirl form of the witch [[BreakoutCharacter Charlotte/Bebe]]]] is introduced in Anime/PuellaMagiMadokaMagicaTheMovieRebellion. Despite the hype for her appearance and her [[TrailersAlwaysLie prominent placement in advertisements for the movie]] she gets very little characterisation or build-up compared to the other magical girls. WordOfGod says that if they ever do make a sequel to Rebellion they intend to do a lot more with her character.

[[folder:Films -- Animation]]
* Po's origins in the first ''WesternAnimation/KungFuPanda''. It looks like we're going to find out toward the end of the movie, but then that turns into TheUnreveal. It's part of the premise of the sequel.

[[folder:Films -- Live-Action]]
* Despite originally being touted as the "secret origin of Spider-Man", ''Film/TheAmazingSpiderMan'' left a lot of unanswered questions about Peter's parents and the nature of their experiments, which were finally addressed in ''Film/TheAmazingSpiderMan2''.
* Likewise, ''Film/TheAmazingSpiderMan2'' doesn't really resolve the situation with Harry's condition, and only introduces the Rhino for a SequelHook concerning the Script/SinisterSix.
* Franchise/MarvelCinematicUniverse:
** A deleted subplot from ''Film/{{The Avengers|2012}}'' focusing on Captain America's attempts at rebuilding his old life (which ended up only alluded to) was included in ''Film/CaptainAmericaTheWinterSoldier''.
** In ''Film/IronMan'', Rhodey looks at the silver prototype Iron Man suit and says, "[[ComicBook/WarMachine Next time, baby]]." Unintentionally funny in that Rhodey had been recast by the next film where he actually gets to wear the armor.
** Early drafts of the script for ''Film/CaptainAmericaTheFirstAvenger'' had Baron von Strucker as a side villain working under the ComicBook/RedSkull, the film's BigBad. The writers felt that using Strucker in such a minor role would be a "waste," so they wrote him out. He eventually made his debut in TheStinger of ''Film/CaptainAmericaTheWinterSoldier'', and was used briefly as one of the villains in ''Film/AvengersAgeOfUltron''.
** According to Joss Whedon, an amazingly awesome, fist-pumping Hulk moment from the climax of ''Age of Ultron'' was cut for disrupting the flow of the finale. He cited this trope as his reason for not revealing what it was, since Marvel can use it in a future film.
* ''Film/BatmanBegins'' is an excellent example. When it ended, the plot was resolved, but there was unresolved romance between Bruce Wayne and Rachel Dawes to provide fodder for the next movie.
* This is attempted with Humma Kavula in ''Film/TheHitchhikersGuideToTheGalaxy'' movie. The Point of View Gun was clearly setting up a plot where he tries to brainwash everyone in the galaxy and take Zaphod's place. Too bad there won't be a second movie to make these things worthwhile.
* ''Film/ThePhantomMenace'' and ''Film/AttackOfTheClones'' ended with several plot points dangling to be picked up in the next installment. Technically, even the last movie of the prequel trilogy, ''Film/RevengeOfTheSith'', ended with dangling plotlines... which were already resolved in the original ''Franchise/StarWars'' trilogy.
** In ''Film/TheForceAwakens'' the fate or identity of Rey's family is never revealed, but it has been confirmed that that issue will be resolved later on in the sequel trilogy. As of ''Film/TheLastJedi'', they have been revealed by Kylo Ren to be [[spoiler:nobody important - drunkards who sold their daughter for drinking money and abandoned her on Jakku]]. Whether this is true or not is yet to be seen.
* In ''Film/TronLegacy'' the son of the bad guy from the original ''Film/{{Tron}}'', played by Cilian Murphy, appears as an Encom board member, but does little save prove his technical savvy and quick mind. With his connection to the history of Tron and the plans for a third movie, it seems likely that he was there to foreshadow a larger role in that plot.
* According to WordOfGod, in ''Film/{{Godzilla 1998}}'' there were going to be other {{kaiju}}, but they got held back to appear in the sequel. Perhaps if they had put them in the movie there would actually have been a sequel.
* In the first Creator/ChristopherReeve ''Film/{{Superman}}'' film, General Zod is roaring to Jor-El, "[[KneelBeforeZod You will bow down before me, Jor-El! Both you and, one day, your heirs!]]" However, he is then cast into the PhantomZone and we have to wait to the next film to see him carry out that threat.
* ''Film/GreenLantern'' has Sinestro, traditionally Hal Jordan's nemesis as a fellow member of the corp. While this fits in with comics continuity, one gets the feeling that this wouldn't be the case if Warner Brothers wasn't hoping to make it into a franchise.
* ''Film/GIJoeTheRiseOfCobra'' is, of course, the story of the rise of Cobra. So Cobra Commander doesn't become Cobra Commander until the last couple of scenes, setting up the sequel ''Film/GIJoeRetaliation''.
* Borderline example in ''Film/TheHobbit'', which includes some of the {{retcon}}s and [[AllThereInTheManual context]] that in the original books were included in the sequel ''Literature/TheLordOfTheRings''. It sort of fits in this trope because unlike the books, ''Film/TheLordOfTheRings'' movies were made first, and ''The Hobbit'' movies are effectively a prequel.
* Averted in the first ''[[Film/TheTerminator Terminator]]''. There were a couple scenes filmed in which Sarah discovered [=SkyNet=]'s origins in Cyberdine and suggested to Reese that maybe they should try to destroy it to prevent the future war as well as a longer ending in which it was revealed that Cyberdine picked up the destroyed Terminator chip and arm, both setting up events that would occur in ''Film/Terminator2JudgmentDay''. James Cameron ultimately had these scenes cut. (Though the sequel still used these ideas)
* ''Film/TheGoldenCompass'' omitted the scenes at the end of the novel on which it is based, in which [[spoiler:Lyra inadvertently betrays her best friend to her father and costs the boy his life.]] We should theoretically have seen those at the start of ''The Subtle Knife.'' Then the whole thing fell through.
* Although the Mutos of ''Film/{{Godzilla 2014}}'' were introduced as {{Canon Foreigner}}s rather than updated versions of classic Creator/{{Toho}} monsters in order to give the film a bit more narrative freedom, Creator/GarethEdwards has jokingly stated that he is contacting the casting agents of creatures like Mothra and [[ArchEnemy King Ghidorah]] so that they can appear in sequels.
* The character of ComicBook/{{Gambit}} has been hit by this several times. He was originally intended to make a cameo in ''Film/X2XMenUnited'', (he ended up just being a name on a computer screen) but it was decided to save the character for ''Film/XMenTheLastStand''. After being written out of that film as well, he finally appeared in ''Film/XMenOriginsWolverine''. After that film was declared CanonDiscontinuity, there were plans to re-introduce Gambit in ''Film/XMenDaysOfFuturePast'', which also failed to materialize. He's currently set to appear in ''Film/XMenApocalypse'', played by Creator/ChanningTatum.
** Jubilee got hit with the same thing. She was originally supposed to appear in ''Days of Future Past'' as one of the future X-Men, but was cut for unknown reasons. She'll instead be used in ''Apocalypse'' as one of the new recruits.
** TheStinger of ''Film/{{Deadpool|2016}}'' has [[spoiler:Wade telling the audience that Cable is planned for the sequel]].
* Early drafts of the script of ''Film/SpiderMan1'' had both the [[ComicBook/NormanOsborn Green Goblin]] and ComicBook/DoctorOctopus as villains. Seeing as how they didn't want to overcrowd the movie with three different origin stories, Doc Ock was cut from the film and later showed up in ''Film/SpiderMan2''
* Early drafts of ''Film/TeenageMutantNinjaTurtles2014'' featured Casey Jones, Beebop and Rocksteady, but all three characters ended up being written out. They'll be appearing in the sequel.

* In the first ''Literature/AnonymousRex'' book, Vincent's [[DeadPartner partner has been killed]], leaving him a cynic, but how it happened is left unsaid. The second book is a {{Prequel}} where at the very end the death happens.
* Creator/BrandonSanderson [[WordOfGod says]] that he has many developments in [[FunctionalMagic BioChroma]] that he plans to put into a sequel to ''Literature/{{Warbreaker}}'' named ''Nightblood''. However, he is not entirely clear on if he will actually write it, and it has been put on hold until after he establishes his ''Literature/TheStormlightArchive'' series in [[Franchise/TheCosmere the same]] [[TheVerse Verse]].

[[folder:Video Games]]
* The $30 expansion for ''VideoGame/SaintsRowTheThird'' titled ''Enter the Dominatrix'' (originally thought to be an [[AprilFoolsDay April Fools joke]], but later revealed to be real) was announced to be canceled but later released for the next game.
* During the final mission of ''VideoGame/StarFoxAssault'', the Star Wolf team (who are [[EnemyMine allies to the Star Fox team for the moment]]) draw off the enemy ships pursuing the Star Fox team, allowing them to reach the game's FinalBoss, and are not seen again, leaving it unclear whether they survived. There has been [[VideoGame/StarFoxAssault another game]] released in the series since then and all three members of Star Wolf did appear, confirming that they did survive, though there is ongoing debate among the fandom over whether that game is canon or not.
* ''VideoGame/BlazBlueCalamityTrigger'' does not explain what exactly happened to Arakune, why Litchi is so bent on rescuing him, what Hazama is up to, who he works for, why Carl is looking for his father, what "Amaterasu" is, who the other five of the Six Heroes are, among many other plot details, creating a MindScrew in general. ''VideoGame/BlazBlueContinuumShift'', the sequel, answers these questions and brings up more. For instance, now that we know Carl is looking for his father because he's an absolute scumbag, we learn that he is a {{Chessmaster}} villain but nothing about what he wants or what he intends to do. Arakune is regaining sentience, but Litchi is about to do to herself what Arakune did before. Bang has the power to close portals to The Edge but has yet to have an opportunity to use it. And so forth.
* ''VideoGame/MassEffect2'':
** The Quarians are worried over a remote star dying far faster than it ought to be. Tali hypothesizes it's due to dark energy affecting the interior of the star, but remarks that no race has the ability or any particular motive to destroy one. Nevertheless, she voices concern over the possibility of an adversary powerful enough to take a star out. The explanation is left open for ''VideoGame/MassEffect3''. Amusingly, this has ended up as an AbortedArc - it's one of the few dangling threads that isn't addressed at all (not even in one of Shepard's emails). Perhaps it will be addressed in the expected new storyline set in the universe.
** [[WhatCouldHaveBeen Originally this was supposed to be the motive for the Reapers.]] They were intended to be interested in stopping the spreading of Dark Energy before it could tear the universe apart. And the key to this was biotics. [[spoiler: This was replaced with the ending of the entirety of the story being about the Reapers as a Rouge AI]]. Given the level of reception of the ending, it seems that this could have been better, though that is likely just because the current ending is so unpopular.
* ''Franchise/{{Pokemon}}'':
** ''VideoGame/PokemonBlackAndWhite'' left a number of loose ends that weren't wrapped up when the story was finished. Fans were expecting a [[UpdatedRerelease "Grey Version"]] following the pattern from past generations, but instead full sequels were released: ''VideoGame/PokemonBlack2AndWhite2''.
** While ''Videogame/PokemonXAndY'' did have Zygarde as a BonusBoss, [[Anime/{{Pokemon}} the Anime]] featured forms for it not found in those games. Because there was no UpdatedRerelease or {{Sequel}} for the Kalos games,[[note]]which averted this Trope for other loose ends...[[/note]] those extra forms were put into ''Videogame/PokemonSunAndMoon'' (and ''its'' {{Updated Rerelease}}s) as a sidequest.
* The Playstation version of ''VideoGame/SoulEdge''[=/=]''VideoGame/SoulBlade'' was intended to feature certain characters as guest characters but in the end there wasn't time to implement them. Among these guest characters would have been Arthur, Kathandra and Monkasei. Arthur would appear in ''[=SoulCalibur=]'' as an optional replacement for Mitsurugi in Arcade machines (mainly for the Korean market but available in American ones too). Kathandra would be renamed to Cassandra and first appear in ''[=SoulCalibur=] II''. Monkasei would be reworked into Yun-Sung and first appear in ''[=SoulCalibur=] II''. Yun-Sung's name would change to Yun-Seong from ''[=SoulCalibur=] III'' onwards.
* ''VideoGame/SuperSmashBros'':
** Bowser, King Dedede, and Mewtwo were meant to be in the first ''Super Smash Bros.'' on the Nintendo 64; they did not get in due to time and budget constraints. Bowser and Mewtwo would eventually make it into ''Melee'', while King Dedede would not join until ''Brawl''. Pit was also considered for ''Melee'' as a retro character (among many other characters), but the Ice Climbers were added over him due to their gameplay potential. Pit would go on to join in Brawl, with an updated appearance, which would lead to [[VideoGame/KidIcarusUprising a new game]] after over two decades.
** Miis were also considered to be added in ''Brawl'', but Sakurai decided against adding them, because, at the time, he could not figure out how to implement them. They join in the Wii U / 3DS iterations as fully customizable characters.
** The [[VideoGame/AnimalCrossing Villager]] was considered to join the battle in ''Brawl'', but Sakurai likewise decided not to include him because ''Animal Crossing'' being about as peaceful as a video game series can get, he couldn't think of any good moves to give him. By the time the fourth game started development, he eventually did find good moves for him, and thus the Villager became playable.
** Creator/ShigeruMiyamoto personally requested VideoGame/PacMan be made a playable character for ''Brawl'' (Pac-Man is his favorite video game character), but Creator/MasahiroSakurai was unable to think of a good moveset at the time. He would make his debut in ''U/3DS'', and indeed, most of his attacks there draw inspiration from other Namco games rather than his home series alone.
* ''VideoGame/Sonic3AndKnuckles'': Due to the game being split in two parts because of time constraints, most plotlines, the second half of the story, and most (if not all) of the Sonic & Knuckles content ended up becoming this.
** Flying Battery was originally going to be a Sonic 3 stage placed between Carnival Night and [=IceCap=], but they choose to save it for Sonic & Knuckles, feeling that this one would be too short otherwise.
** Hidden Palace was going to be a [[ExactlyWhatItSaysOnTheTin hidden]] Sonic 2 stage where Sonic would gain his [[SuperMode Super form]] after collecting all Chaos Emeralds, but had to be scrapped due to time constraints. Two years later, the stage was incorporated into Sonic 3 & Knuckles, albeit using different layout, graphics and music, but keeping its concept, function (replacing Super Sonic with Hyper Sonic) and lore (albeit altered to fit with the game and the established canon), even making the area more of a central element in the story. Eventually, the 2013 smartphone Sonic 2 port added back the Zone as an extra bonus, but it stripped it off its functions and lore and changed it into more of a prehistoric-themed stage to differentiate it from the S3&K incarnation.
** A more minor ''Sonic'' example was the Sunset Park Act 3 theme from ''VideoGame/SonicTheHedgehogTripleTrouble''. It was originally supposed to be used in ''VideoGame/SonicTheHedgehogChaos'', but was DummiedOut before finally being used in ''Triple Trouble''... to the delight of many fans, who consider it to be [[CrowningMusicOfAwesome the best song]] [[SonicTheHedgehog/AwesomeMusic in any 8-bit Sonic game]].
* Nova Terra was the main character of the ''{{VideoGame/Starcraft}}'' GaidenGame Starcraft:Ghost, a third-person shooter. The game went through a long DevelopmentHell until it was finally cancelled, but Nova becomes an important side character in ''VideoGame/StarcraftII''.
* Some elements of ''VideoGame/WarcraftII'''s backstory ([[AllThereInTheManual especially concerning]] [[CosmeticallyDifferentSides the different human factions]]) weren't seen in ''VideoGame/WarcraftIII'', but returned with a vengeance in ''VideoGame/WorldOfWarcraft''.
* Shigeru Miyamoto has always liked the concept of riding a dinosaur that eats enemies (a similar dragon appears in ''VideoGame/DevilWorld''), and he always intended one to appear in the ''Franchise/SuperMarioBros'' series. However, due to technological limitations, he couldn't include one in either ''VideoGame/SuperMarioBros1'' or ''VideoGame/SuperMarioBros3''. The leap to 16 bits in ''VideoGame/SuperMarioWorld'' gave them enough power to finally introduce Yoshi to the ''Mario'' universe.

[[folder:Web Original]]
* In ''Series/{{Noob}}'', Omega Zell and Gaea were meant to both have something big happen to them at the end of Season 5, which was supposed to be the last of the webseries. Part of Season 5's production ran concurrently with a crowfunding campaign meant to finance a movie that would be a sequel to the webseries. When the crowdfunding turned extremely successful, the creator decided to move these big moments to ''Film/NoobLeConseilDesTroisFactions'' so they could be made more impressive than if they had happened during the webseries.

[[folder:Western Animation]]
* ''WesternAnimation/AvatarTheLastAirbender'' was initially supposed to go in-depth about the origin of the Avatar Cycle. This was cut for time and instead covered in season two of ''WesternAnimation/TheLegendOfKorra''.
** ''Korra'' itself has this to a smaller extent in the form of Kuvira, who appeared briefly in the finale of season 3 (with a very noticeable character model and soundtrack, mind you) before returning with a much larger role in season 4.
* ''WesternAnimation/TheSimpsons'' episode "[[Recap/TheSimpsonsS14E12ImSpellingAsFastAsICan I'm Spelling as Fast as I Can]]" was going to have a LeadIn where Bart realises he wasted his summer and rushes all the activities he intended to do on the last day. It ended up being cut for time and used in "[[Recap/TheSimpsonsS17E21TheMonkeySuit The Monkey Suit]]" instead, three seasons later.
* The ''WesternAnimation/StevenUniverse'' episode "[[Recap/StevenUniverseS3E5HitTheDiamond Hit the Diamond]]" was going to have a scene where Steven gives nicknames to the Ruby Squad, but it ended up being cut. It took until "[[Recap/StevenUniverseS3E23BackToTheMoon Back to the Moon]]", the Squad's second appearance, for the nickname scene to happen.