For almost a full season, the plucky folks who [[WeHelpTheHelpless help those in need]] have defeated MonsterOfTheWeek after MonsterOfTheWeek, protected the space-time continuum from invading aliens, stopped an {{Antimatter}} explosion from removing North America from the face of the planet, and saved the [[OurPresidentsAreDifferent President]].

Now, however, they are vexed by someone who seems to know their strengths, their weaknesses, and everything in between. They're outmaneuvered, outnumbered, and outsmarted. The season ends with the villain gloating over them, saying their most dangerous tasks up to that point have simply been tests he has engineered.

The Arc Welder cometh.

Arc Welding is a retroactive form of ContinuityCreep that occurs when a series which has heretofore been episodic {{retcon}}s itself so that it's all linked in a StoryArc. The most common approach to Arc Welding is probably when one antagonist, hidden up to that point, is responsible for all the major threats the protagonists have faced thus far.

Alternatively, several arcs might be revealed to part of a larger MythArc. This is rarer, possibly because it's harder to do well and shows that would benefit from it might not last long enough to play out the {{retcon}}.

Arc welding is different from StoryArc or MythArc because it is always retroactive. Series that start out with a StoryArc or MythArc already in place generally aren't welded. If something were already part of an arc, it wouldn't need welding.

The creators may be simply putting unrelated crap together for the sake of using up the budget now that they're renewed. It can be also be a stroke of brilliance, the creators now realizing an underlying theme of their work on the series thus far. Lastly, Arc Welding itself can be plotted from the beginning, as TheReveal. In the absence of the confirmation provided by the WordOfGod, Arc Welding is YMMV.

Compare CanonWelding, which ties together different series, and InnocuouslyImportantEpisode, which retroactively ties a seemingly unrelated event into an existing StoryArc. See also MetaOrigin, PatchworkStory, HyperlinkStory. Under the right circumstances, GreaterScopeVillain and GreaterScopeParagon can both come into play as well, especially if the events of seemingly unrelated parts of a story are later revealed to have been caused by or tied to a specific villain or specific hero.

[[JustForFun/IThoughtItMeant Has nothing to do with welding metal using arcing electicity.]] For info on that, go [[ here]]. For a minigame on that, go to ''VideoGame/MetroidPrime3Corruption''.



[[folder:Anime and Manga]]
* ''Manga/{{Bleach}}'': Was the plot up to BigBad Aizen's defeat a self-contained arc unconnected to the Thousand Year Blood War? Hell no! Aizen's deeply involved in many of the events that set up the War, but the Final Arc's BigBad was secretly involved in many earlier events as well. While the first arc appears to be a protracted chess game between Aizen and Urahara, the final arc answers the question of ''who had provided the chessboard''. The final arc connects events as disparate as the death of Ichigo's mother, Rukia's execution, Ichigo's substitute shinigami badge, Aizen's hollowfication experiments, Ryuuken's hatred of Quincies, and more. WordOfGod has indicated that the arc welding actually occurred at the end of the Soul Society arc when Creator/TiteKubo realised how to end the story on the basis of what he'd written up until that point. This discredited a fan theory that the length of the Arrancar Arc was a result of Kubo stalling because he hadn't figured out how to end the plotline. Thus far, {{Rewrite}} {{Retcon}}s have been avoided, although several events (most particularly Masaki's death) have had to be {{Revision}}ed.
* ''Franchise/{{Naruto}}'':
** A minor example: A {{Filler}} episode of [[Manga/{{Naruto}} the original series]] revealed that Mizuki attempted to steal the kinjutsu scroll on [[BigBad Orochimaru's]] orders. This revelation occurred around episode 160 or so, and Mizuki stole the scroll in episode 1.
** A major example: Tobi is largely responsible for/connected to the origins of Naruto (he unleashed the Nine-Tailed Fox on the Hidden Leaf Village, forcing the Fourth Hokage to seal it in Naruto), Sasuke (he helped Itachi with the Uchiha massacre), the messed-up state of the Hidden Mist Village in Part 1 (he was mind-controlling its leader), etc.
** ''Kakashi Gaiden'' was originally just a short prequel arc detailing the origin story of Kakashi. Years later, it turned out to also be the beginning of the origin story for Tobi himself.
** The Sage of the Six Paths is first mentioned as being the founder of the ninja arts (and the first guy with the [[MagicalEye Rinnegan]]), but is later revealed to be both the ancestor of the Senju, Uchiha, and Uzumaki clans, ''and'' the guy who split the almighty Ten-Tailed Beast into the nine different Tailed Beasts that exist today, creating the MOON on the whole process.
* ''Every'' subplot in ''Anime/ExcelSaga'', which were all PlayedForLaughs, actually got tied together in the [[GainaxEnding surprisingly serious finale.]]
* In Franchise/SailorMoon Creator/DiC tried to do this to all the bad guys that appeared during the second season. Then later [[spoiler: Creator/NaokoTakeuchi did this with the bad guy ''Chaos'' at the end of the [[Manga/SailorMoon manga]] who was supposedly responsible for the appearance of all the previous {{Big Bad}}s]].
* ''Manga/TenjhoTenge''. Every bad thing that ever happened to anyone turned out to be the work of [[spoiler:the protagonist's dad]]. Even the stuff that happened centuries ago.
* ''Anime/YuGiOhGX'' has this with season four, where it is revealed that the release of the Sacred Beasts, the Light of Destruction, and Yubel's schemes were all used by the final BigBad Darkness for...something.
* ''Anime/YuGiOh5DS'', the villains of the first major story arc are Roman Godwin and [[spoiler:his brother Rex]], who are revealed to be responsible for the Zero Reverse incident that severed Domino City in two. The next season revealed Roman's turn to evil was engineered by the AncientConspiracy Yliaster as a plot to destroy Domino City with Zero Reverse. After the three leaders of Yliaster were defeated, the founder of the organization, Z-one, appeared as the final antagonist of the series, picking up the trio's plans to destroy Domino. The final arc also revealed that Paradox, the antagonist of ''Anime/YuGiOhBondsBeyondTime'', was also an agent of Yliaster working on a secondary plan in that film.
* Chapter 170 of ''Manga/YuYuHakusho'' confirms that [[spoiler:everything that happened in the series was a result of ''King Enma's'' actions. He created falsified reports of demon crimes in the human realm, let evil demons into the human realm, and even brainwashed innocent demons for his Spirit Detectives to finish off, increasing Enma's reputation within Spirit World, since the Spirit Detectives were under his command. This gave Enma the authority to erect a barrier between the three realms, as supposed demon "crimes" would create the illusion that this was a righteous act, and not totalitarian, since the spirit energy unused by humans was a valuable resource to the Spirit World.]]
* ''Manga/PokemonSpecial'' tends to do this:
** Both good guys and bad unexpectedly show up in later arcs with gambits ahoy, but FRLG and Emerald take the cake. FRLG was a result of all the previous arcs while Emerald was a direct consequence of FRLG. For reference, Emerald was the ''sixth'' arc, and Pokemon in general rarely bothers with continuing plots across multiple games/series/whatever.
** Volumes 29 (climax of Emerald) and 38 (climax of Diamond and Pearl, beginning of Platinum) brought together and resolved so many plot lines from different arcs to the point that the {{HSQ}} was reached.
* Happened quite a lot in ''Manga/FistOfTheNorthStar''. A few volumes after Kenshiro's TokenMotivationalNemesis Shin was killed off, it is revealed that the reason why he turned on Kenshiro in the first place was because Ken's stepbrother Jagi (a later villain) persuaded him. Later, Shin is revealed to have only faced Kenshiro to build upon the Gosha Stars' lie that Yuria died as a result of her suicide attempt, so that Raoh won't be able to find her.
%%* ''Literature/TheTatamiGalaxy'' is built around this trope.
* ''Anime/PrettyCureAllStars DX 3'' did the same thing the manga ''Manga/SailorMoon'' did with Black Hole. Though since ''DX 3'' is mostly non-canon to the series they're connected to, it kinda really doesn't count.
* This is pretty much the whole reason the ''Manga/MobileSuitCrossboneGundam'' manga exists: without it, ''Anime/MobileSuitGundamF91'' and ''Anime/MobileSuitVictoryGundam'' come off as two unconnected stories that just happen to be set in the UC timeline. With it, the stories are tied together into a larger overarching narrative with the Jupiter Empire and its aristocratic oligarchical philosophy as TheManBehindTheMan of both the anime series' {{Big Bad}}s.
* ''Anime/DanganRonpa3'' ties together the plot arcs of [[VisualNovel/DanganRonpa Makoto Naegi and the 78th class of Hope's Peak Academy]], [[VisualNovel/SuperDanganRonpa2 Hajime Hinata and the 77th class]], and [[VideoGame/AbsoluteDespairGirls Komaru Naegi and the events in Towa City]].

[[folder:Comic Books]]
* Creator/AlanMoore is famous for re-visioning and changing characters to suit his conception, however he always ensures that the stories preceding his work were given a good conclusion with all background details and subplots resolved so that ''he'' can get on and [[AndNowForSomethingCompletelyDifferent do something different]], he states that he does this because readers would otherwise feel cheated that the stories they followed had no payoff.
** In ''ComicBook/SwampThing'', he famously resolved Alec Holland's quest to become human again by choosing to TakeAThirdOption, [[spoiler:the Swamp Thing was never Alec Holland, the scientist was DeadAllAlong and his consciousness was absorbed by a swamp creature who believed he was "Alec Holland".]] This DownerBeginning resolved the FailureIsTheOnlyOption nature of the premise, re-purposed and recycled supporting characters to give them new roles in a DarkerAndEdgier world and Moore even allowed [[spoiler:Alec Holland a HappyEnding reunion with his wife during Swamp Thing and Etrigan's journey to the afterlife]].
** In ''Comicbook/{{Miracleman}}'' a DarkerAndEdgier reboot of the childish British originals, the bizarre and fantastical Mick Anglo 50s stories [[spoiler:are retconned into artificial memories via LotusEaterMachine by the BigBad]], ensuring that the old stories had a context and important to the modern version.
* ''ComicBook/BuffyTheVampireSlayer'':
** The end of Season 8 sets up the the background of {{ComicBook/Fray}}, written 10 years earlier.
** When Whistler shows a vision of the future to come in a world without magic, it's clearly the world of {{ComicBook/Fray}}, if you notice the hovercars.
* ''ComicBook/CerebusTheAardvark'' did this ''a lot''. There were very few minor, throwaway characters. Just about anyone who talked to Cerebus at some point is revealed to be important to the plot somehow.
* The comic ''ComicBook/{{Transmetropolitan}}'' starts its MythArc with issue #13 (the Year of the Bastard storyline), but starts Arc Welding sometime around issue #30. Though it takes a while, events from the first issue are eventually revealed to have had an impact all the way to the last.
* One of the highest quality examples of this is Creator/DonRosa's ''ComicBook/TheLifeAndTimesOfScroogeMcDuck'' series, which takes every random reference Creator/CarlBarks ever made to Scrooge's past and puts together a comprehensive, sensical and engaging character biography. If the Eisner award is to be believed, it ''really'' worked.
* Creator/GeoffJohns did this in the Franchise/GreenLantern books, introducing an "emotional spectrum" that people can draw power from. The Green Lantern Corps fall square in the middle at green willpower; with red rage, orange avarice and yellow fear on one side and blue hope, indigo compassion, and violet love on the other. Not only are existing characters being tied into the spectrum (villainess Star Sapphire tapping into love energy, for example), but Johns has established whole rival corps for each (like yellow ring-wielder Sinestro starting his own Sinestro Corps of fear).
** It all started with his revival of Hal Jordan. The Retcon that explained away Hal's villainy also accounted for the periods of self doubt the character had been through, the graying of his hair, the reason the Spectre chose him as a host, and the reason why Hal was tempted by the power he stole while Kyle wasn't.
** Before Johns, there was Steve Engelhart, who across several series and years tied together previously unrelated characters including the Creator/JackKirby version of Manhunter from the 1970s, the Zamarons, and the recurring mystery villain the Predator by revealing that they were all connected to the Guardians. Around the same time, Marv Wolfman showed that the Controllers from the ''Comicbook/LegionOfSuperHeroes'' were also a Guardian offshoot.
* In the Franchise/{{Marvel Universe}}, The writers and editors of all of its comics revealed that [[spoiler: Weapon X is in fact controlled by an organization that has existed since before WWII called Weapon Plus, [[NebulousEvilOrganization a secret governmental organization hellbent on eradicating mutants]], who is responsible (directly or indirectly) [[GreaterScopeVillain for a LOT of the crappy stuff that Wolverine went through in his life. Also, they are (directly or indirectly) responsible for the existence of many heroes and villains of the Marvel Universe, not just Wolverine himself.]] They created project rebirth, wich makes them indirectly responsible for the creation of Captain America and Isaiah Bradley(or to be more specific, the super soldier serum, AKA Weapon I). They also created Weapon II(a weird squirrel with Wolverine's powers), The Skinless Man(Weapon III), Nuke(One of Daredevil's villains and Weapon VII), X-23, Deadpool, Huntsman(Weapon XII), Fantomex(Weapon XIII), The Stepford Cuckoos(Clones of Emma Frost and Weapon XIV), Ultimaton(Weapon XV), Allgod(Weapon XVI) and according to WordOfGod, they are also responsible for creating or empowering many more unknown characters, both heroes and villains. In some comics, it's also implied that they might have been involved with the prison experiments that gave Luke Cage his powers, the program that created the sentinels and the Red Room Black Widow Ops organization that created the multiple Black Widows(like Natasha Romanoff and Yelena Belova). The organization has also been known to work with and provide money and ressources to other villainous organizations(especially those that hate the X-men) like A.I.M., HYDRA, The Hellfire Club, ROXXON, The Purifiers, OSCORP, ect...Later on, it's revealed that Weapon Plus was created and controlled by an even GREATER greater scope villain known as Romulus. He claims to be responsible for EVERYTHING that happened in Logan's life and more, with plenty of evidence to back up said claim (Such as immense intimate knowledge of Wolverine's life, for example). The aforementioned John Sublime was pulling strings in the program as well, and to make things even more confusing, WordOfGod from the writer of the very first Weapon X story indicated that the original greater scope villain was going to be Apocalypse, but this never saw print for unknown reasons. Needless to say, this was revealed decades after weapon X's first appearance, wich is ironic, because Weapon Plus made it's first appearance more than 75 years before it was named or written into Marvel canon, in Captain America's first appearance. Granted, Weapon Plus isn't fought often by the superheroes, but despite what anyone might believe, they are still active and plaguing the Marvel Universe with it's atrocious experiments and horrifying creations...]]
* ''ComicBook/{{Wolverine}}'': In volumes 3 and 4, and in ''Wolverine: Origins'', Marvel decided to reveal {{Wolverine}}'s [[ExpansionPackPast long and complicated]] backstory. It turns out just about every bad thing that ever happened to him was orchestrated by a single figure known as Romulus. This is reiterated in the handbook ''Wolverine: Weapon X Files'', where almost every entry has a note saying "this was probably a plan by Romulus".
* James Robinson's ''Comicbook/{{Starman}}'' managed to provide a coherent connection between the [[LegacyCharacter various characters who had used that name]], even though with one or two exceptions, none of them [[InNameOnly had any relation, or indeed even the same powers]].
* In ''[[Comicbook/UltimateSpiderMan Ultimate Spider-Man]]'', several {{Batman Cold Open}}s involving him fighting some villain who attacked "Roxxon Industries" were welded together when the CEO of that company (a person rather lacking in common sense) hired some mercenaries to bring him in for questioning about why he was fighting those people.
* Creator/KurtBusiek's ''Comicbook/AvengersForever'' story indulges in arc welding throughout, revealing that [[spoiler: every action ever taken by the villain Immortus was done in the interests of preventing the destruction of humanity by the Time Keepers. A number of seemingly unrelated plotlines turned out to have taken place under the influence of Immortus.]]
* One storyline of ''Franchise/ArchieComics'' was the result of the events in previous stories: over the past couple of months, Jughead has experienced cranial injury from different objects (box of comic books, flamingo statue, typewriter, football, and a [[ItMakesSenseInContext ball of hamburgers]]). Somehow this causes his body metabolism to go in reverse; wherein usually any food he eats is instantly digested (explaining why he stays so thin), all the foods he eats now turn into fatty tissue, resulting in Jughead gaining a lot of weight overnight.
* ''[[Comicbook/ArchieComicsSonicTheHedgehog Sonic the Hedgehog]]'': During the "Enerjak Reborn" arc, [[MadScientist Dr. Finitevus]] reveals how everything he's done since his introduction has been part of his grand plan to create a new [[PhysicalGod Enerjak]]. It's also revealed that he was the (at the time) unnamed Echidna scientist who attempted to return Chaos Knuckles to normal by draining his power (the backfire of which is what rendered him [[EvilAlbino albino]]).
** Issue 233: many of [[spoiler: Geoffrey St. John]]'s past actions are shown in a new light, as it's explained that he was working on a master plan to [[spoiler: make Ixis Naugus king of Acorn]].
** When the [[QuirkyMinibossSquad Destructix's]] backstories were revealed, a bit of this was applied to Sergeant Simian and Predator Hawk. They were shown to, in the past, have been members of the Gorilla Guerillas and the Battle Bird Armada (respectively), groups that were introduced after they were, but before the story arc that revealed their past memberships.
* An early story in the first ''ComicBook/{{Deathstroke}}'' series revealed that a character who had appeared once in a flashback story years earlier had in fact been seeking vengeance on Slade for years and was responsible for the kidnapping and maiming of Slade's younger son Joseph and the recruitment of his older son Grant for an experiment that would kill him.
* During his ''Comicbook/IronMan'' run, Frank Tieri created a rival for Tony named Tiberius Stone. Years later, Creator/DanSlott brought Tiberius out of Comic Book Limbo and revealed that he was the ancestor of Tyler Stone, one of the major villains from ''Comicbook/SpiderMan2099''.
* In ''ComicStrip/NonSequitur'', Wiley frequently used three separate sets of recurring characters: {{everyman}} Joe and his drinking buddy, Bob, BrattyHalfPint Danae and Sunday-only character, diner-owner "Offshore" Flo and her tall-tale telling patron, Eddie. Eventually, after years of the characters appearing in their own spheres, Wiley brought them all together: Joe and Bob are brothers, Flo is their mother and Danae and her younger sister are Joe's kids. (Eddie's still just "Eddie").
* Pretty much everything in [[Comicbook/GrantMorrisonsBatman Grant Morrison's run on Batman]] ties back to either Dr. Hurt and the Black Glove, or [[spoiler: Talia]]'s Leviathan organization.
* Another Batman example: the climax of the ''[[ComicBook/BatmanTheBlackMirror Black Mirror]]'' arc reveals that [[TheSociopath James Gordon Jr.]] was involved, one way or another, in pretty much ''everything'' villainous that occurred over the course of the arc. He also implies that he was the one who inspired ComicBook/TheJoker to cripple Barbara back in ''Comicbook/TheKillingJoke'', though it's unclear if that's true or if he's just screwing with her.
* Jonathan Hickman's run of ''ComicBook/TheAvengers'' reveals that ComicBook/CaptainUniverse, ComicBook/TheNewUniverse and its remake Newuniversal all share the same origin.
** In the process of doing this, it merges both versions of the New Universe, stating that the original was another form of the reimagined version.
* Since DC Comics rebooted the line with the ComicBook/{{New 52}} in 2011, each September issue has been been part of a themed month, such as the 2012 issues being "Zero issues " exploring the revised origins of DC's heroes. Rather than detail the series, ''Franchise/TheFlash'' instead tied the issues into the on-going narrative.
** 2012: Zero issue - The debut of [[spoiler:Daniel West]], who would be revealed as the New 52's Reverse Flash over the course ofvthe next year.
** 2013: Villain issues - The issue devoted to the Reverse Flash ties directly into the ongoing story arc of the time, whilst issues devoted to Grodd and the Rogues led directly into the Rogues's ''ComicBook/ForeverEvil'' mini-series.
** 2014: Future's End - The issue ties directly into the Future Flash story arc that had been going on since April.
* ''ComicBook/TheCloneSaga'' had one moment where Peter is arrested for deaths that were connected to the clone Kaine. To his horror, the times those people were killed were [[ComicBook/KravensLastHunt during the time he was buried alive]] and he has no alibi without blowing his secret identity.
* In one of the oldest examples, ''Strange Tales'' #146 reveals that A.I.M. and the Secret Empire, previously treated as brand-new, independent threats to Comicbook/NickFury, Comicbook/IncredibleHulk, and Comicbook/SubMariner are just front organizations for a regrouped Hydra.
* ''ComicBook/{{Onslaught}}'' does this with three elements:
** When Bishop first appeared in the Franchise/XMen comics, a key part of his backstory was finding a garbled tape of Jean Grey talking about a traitor in the X-Men's ranks who'd killed everyone, seemingly starting with Professor Xavier and that they shouldn't have trusted and something or someone. Furthermore, an older man known as the Witness is seemingly an older Gambit, being the only survivor, which led Bishop to suspect that Gambit was the traitor. When ''Onslaught'' finally kicked off, the one-shot ''Onslaught: X-Men'' tied the tape into its plot, showing it in its entirety: Professor Xavier himself was the traitor (this ''is'' ''Onslaught'' after all), Jean believed Juggernaut was the first to die, and that the X-Men should have suspected that Xavier's mindwipe of Magneto in ''ComicBook/FatalAttractions'' could (and would) backfire (as it's what led into Onslaught).
** A bit of [[CharacterizationMarchesOn characterization marching on]] was [[TeacherStudentRomance Professor Xavier having romantic feelings for Jean Grey]] in the early issues. Onslaught delighted in showing Jean this in trying to get her to join his side.
** Additionally, as noted before, Onslaught has his roots in the events of ''ComicBook/FatalAttractions'', as Xavier mindwiping Magneto following his ripping out Wolverine's Adamantium is what led to Onslaught's existence.
* In one of the most jaw-dropping examples out there, ''[[ComicBook/DCRebirth DC Universe: Rebirth #1]]'' revealed the true creator of ComicBook/TheNew52 universe: [[spoiler:[[ComicBook/{{Watchmen}} Dr. Manhattan]]. The experiment at the end of the story gave birth to this world. Furthermore, the pre-''ComicBook/{{Flashpoint}}'' and ''New 52'' universes are the same universe.]]
* In ''ComicBook/XMen'', several originally unrelated stories and characters eventually came together throughout the '90s to show that the villains Mr. Sinister and Apocalypse had been rivals since the Victorian era, and it was Sinister's attempts to create a mutant powerful enough to destroy Apocalypse for good that motivated his manipulations of Comicbook/JeanGrey and the Summers brothers and ultimately gave rise to the birth of Nathan Summers, a.k.a. Cable. Of course, this did give rise to the famous ContinuitySnarl that is Cable's backstory, which involves a post-apocalyptic future, a sibling from ''another'' post-apocalyptic future, an alien virus that turns flesh into cybernetic metal, a clone mother who launched a demonic invasion of Earth, and a crazy clone "brother."
* ''Comicbook/{{Supergirl}}'': In a ''Superman Family'' issue, writer Jack C. Harris revealed that most of criminals and Villains-Of-The-Month that bedeviled the titular heroine during his run were controlled by Lesla-Lar, Supergirl's first villain whom she defeated in a story written twenty years prior.
* Creator/AlEwing's run of ''ComicBook/TheUltimates2015'' ties in that series' main storyline with elements from Matt Fraction's run of ''Defenders'', Kieron Gillen's ''Iron Man'', and Grant Morrison's ''Marvel Boy''. [[spoiler:In fact, the main villain turns out to be something mentioned once in a throwaway line of the later.]] It also ties these elements in to something established in Ewing's work on ''New Avengers'', the previous iterations of existence (of which the current Marvel Universe is the eighth or seventh, depending on who's asked).
* In its first arc, Geoff Johns' run on ''ComicBook/TeenTitans'' does this with two of the Titans' oldest enemies, [[SinisterMinister Brother Blood]] and [[DemonLordsAndArchDevils Trigon]]. Specifically, it's revealed that the former's cult is actually a ReligionOfEvil built around the worship of the latter.

[[folder:Fan Works]]
* Dr. Brainstorm from ''Fanfic/CalvinAndHobbesTheSeries'' [[BlatantLies claims]] to have done this in order to build the [[DoomyDoomsOfDoom Doom]] [[SpaceStation Satellite]].
** Played straight in "Our Solemn Hour", [[spoiler: where [[BigBad Holographic Retro]] reveals he was behind the power outage in "Surge", the return of [[{{Technopath}} Electro]] in "Part Three", the "save Aankor" plan in "Invasion", and the FreakyFridayFlip in "Bodyswap" (though he intended it to [[LaserGuidedAmnesia erase their memories]]).]]
* The ''FanFic/HarmonysWarriors'' series of stories does this to tie together the stories based on the X-Men movies and those based on the Franchise/MarvelCinematicUniverse: Gustav, the BigBad of ''X-Questrians: First Class'', is revealed in ''Captain Equestria'' to have been a member of HYDRA back in the day, serving as Hoity Toity/Red Skull's [[TheDragon Dragon]].
* In the ''Fanfic/PonyPOVSeriesChaosVerse'', the BigBad [[spoiler: [[EnemyWithout Nightmare Phobia]]]] is revealed to be behind nearly every problem the Mane Six have for most of the show up to "Luna Eclipsed" (excluding Discord) by [[ManipulativeBastard manipulating their emotions]] to make them act in self-destructive ways.
* Then in the ''FanFic/PonyPOVSeries'' proper, a single chapter ("The Connection") manages to tie together EVERY arc, story and alternate universe together into a single story of redemption, salvation, hope and change. Namely, [[spoiler: when the alicorn version of Twilight from the [[BadFuture Dark World]] finished saving it, she then created an alternate timeline by blowing herself up (twice!) into four beings -- Shining Armor, [[ForWantOfANail whose presence would prevent Twilight from creating the Dark World by keeping her own canon from melting down]], and the three [[MysteriousWatcher Interviewers]] who've been recording this story and guiding the heroes the whole time.]]
* ''Fanfic/ReimaginedEnterprise'' puts together many different disconnected references and plot points from ''Franchise/StarTrek'' canon into new stories.
* ''Fanfic/TheLionKingAdventures'':
** [[spoiler: Death]], the BigBad of Series 3, reveals in ''Darkness Falls'' that he was directly responsible for ''everything'' that happened to Simba and his friends throughout the series.
** ''The End'' reveals that Series 5 BigBad [[spoiler: [[GodIsEvil The Writer]]]] is the UltimateEvil who created every other villain in the series, all for no other reason than [[ForTheEvulz his own amusement]].
* In the ''FanFic/FacingTheFutureSeries'', it's revealed in ''A Family Thing'' that [[ArchEnemy Vlad]] was behind Vortex and Nocturne's escape from Observant custody, and their subsequent actions, in ''Hearts and Minds''.
* It's [[FandomSpecificPlot very common in the fandom for]] ''Franchise/SpyroTheDragon'' to combine ''VideoGame/TheLegendOfSpyro'' continuity with the original series. Oftentimes, it's used to bring characters from the older games into the new ones, ''especially'' the other dragons. Other times, it's just used to attempt to bring the two alternate plotlines together.
* Fanfic/TheDearSweetieBelleContinuity originated as disparate stories (Rarity's letter to Sweetie Belle, Luna and Shining Armor's affair, the romantic setups of ''Morning Glory'') which the author realized fit together well. He also attempted to tie in another of his stories regarding an AU where Luna took over, [[ but that didn't work out so well]].
* ''Fanfic/FlaihhsamSSpahkh'' does a fair amount of this. Spock's appearance on Romulus in the TNG two-parter "[[Recap/StarTrekTheNextGenerationS5E7Unification1 Unification]]" is referred to, and he has since become the official ambassador to Romulus, {{foreshadowing}} his relationship with the Romulans in the '09 ''Film/StarTrek'' movie, and spearheads the effort by the Federation to get the cloaking device for the USS ''Defiant'' following the clusterfuck with the USS ''Odyssey'' in "[[Recap/StarTrekDeepSpaceNineS02E26TheJemHadar The Jem'Hadar]]".
* ''[[Fanfic/GuardiansWizardsAndKungFuFighters Guardians, Wizards, and Kung-Fu Fighters]]'' does this with a couple of secondary antagonists from ''WesternAnimation/JackieChanAdventures''. Recurring crime boss Bartholomew Chang and oneshot relic thief Vanessa Barone are presented as the heads of the Asian and European branches of the Dark Hand, respectfully, despite neither having a known connection to the organization in canon.

[[folder:Films -- Live-Action]]
* In ''Film/{{Scream 3}}'', the killer, [[spoiler: Roman]], reveals that he was responsible for the events of [[Film/{{Scream 1996}} the first movie]] and [[Film/{{Scream 2}} the second movie]], being the one who inspired [[spoiler:Billy]] and later [[spoiler: his mother]] to start killing.
* [[Film/TheHowling Howling VII]] ''tried'' to do this, and actually did an admirable job. Unfortunately, the director chose to have the exposition delived in massive {{Info Dump}}s. The Website/AgonyBooth had a field day with it:
--> ''If you do, put this story in several five-minute segments. We wouldn't want to exhaust the poor Inspector, would we?''
* In the Franchise/MarvelCinematicUniverse, the later Phase One films dealt with an object of power called the Tesseract and TheStinger to ''Film/TheAvengers2012'' revealed that Thanos was that film's GreaterScopeVillain. TheStinger of ''Film/ThorTheDarkWorld'' would then tie those two together with its own MacGuffin, the Aether, when it stated that the Tesseract and the Aether are both Cinematic Universe versions of [[ComicBook/TheInfinityGauntlet Infinity Stones]], which Thanos has historically been involved with in the comics.
** In a smaller instance, in the first ''[[Film/IronMan1 Iron Man]]'' movie we are told that Howard and Maria Stark died in an accident when Tony was younger. Not much thought is given to this since unfortunately, car accidents are a common occurrence in real life. Then, years later during ''Film/CaptainAmericaTheWinterSoldier'', we find out via FreezeFrameBonus that [[spoiler:the accident was deliberately caused after the Starks were targeted for assassination by HYDRA]]. ''Film/CaptainAmericaCivilWar'' follows up on this by confirming that [[spoiler: not only did HYDRA order the assassination, but Bucky was the one to carry it out, savagely beating the Starks to death.]]
* ''Film/{{Spectre}}'' establishes that [[NebulousEvilOrganization SPECTRE]] [[HijackedByGanon was behind]] the group QUANTUM from ''Film/CasinoRoyale2006'' and ''Film/QuantumOfSolace'', as well as Raoul Silva from ''Film/{{Skyfall}}''. Behind-the-scenes, QUANTUM was created as a SuspiciouslySimilarSubstitute for SPECTRE, as SPECTRE's film rights were ScrewedByTheLawyers for decades. When those film rights were finally dealt with, it was only natural for the movies to reintroduce SPECTRE and pull a HijackedByGanon.

* ''Literature/AwakeInTheNightLand'', which is set in the universe of Creator/WilliamHopeHodgson's ''Literature/TheNightLand'', linked this book to ''Literature/TheHouseOnTheBorderland'' by stating that the titular house is the entrance to the House of Silence of The Night Land, but in the past.
* ''Franchise/TheDarkTower'' series is a major ArcWelding project for the works of Creator/StephenKing, bringing together multiple previously introduced concepts and characters for a SavingTheWorld plot of epic proportions. It had long been established that many of King's works took place in the same continuity (the towns of Derry and Castle Rock were recurring locations, and there were a few characters that appeared in multiple works), but their plots had generally stayed independent from one another before that point. ''The Dark Tower'' reveals that '''all''' of his works coexist with each other, even when they seem to take place in different universes--because his world is a {{multiverse}} where multiple parallel Earths exist simultaneously, and certain gifted characters can travel from one parallel world to another. To elaborate:
** The vampires from ''Literature/SalemsLot'' and the "Low Men" from [[Literature/HeartsInAtlantis "Low Men in Yellow Coats"]] are both part of a massive army commanded by the mysterious Crimson King from ''Literature/{{Insomnia}}''. Randall Flagg from ''Literature/TheStand'' and ''Literature/TheEyesOfTheDragon'' is the Crimson King's [[TheDragon Dragon]], serving as his emissary on Earth.
** The psychics Ted Brautigan (from "Low Men in Yellow Coats") and Dinky Earnshaw (from "Literature/EverythingsEventual") are two of many psychics being systematically tracked down and recruited by the Crimson King's agents so that they can harness their abilities to bring the Dark Tower crashing down. Though never stated, it's presumed that characters like Danny Torrance from ''Literature/TheShining'' and Carrie White from ''Literature/{{Carrie}}'' are similar such psychics, and that their abilities could also bring down the Tower if so utilized.
** The mystical "Turtle" entity from ''Literature/{{It}}'' is "Maturin", one of several Guardian spirits that exists to protect the Dark Tower. Each world has its own Guardian (in Roland Deschain's world, for example, it's a bear called "Shardik"), and they all oppose the Crimson King in his quest to destroy reality.
** Project Arrowhead from ''Literature/TheMist'' is one of the few agencies ever to successfully discover the nature of the Multiverse, and their theory about the existence of parallel worlds was 100% true. Also, the titular mist was a "thinny", a weak spot in the barrier between parallel worlds that characteristically emits white fog and high-pitched keening noises that can drive a person insane. And the monsters from the mist were creatures from "Todash", the primordial darkness between worlds from which the Crimson King was born.
** The world of ''Literature/TheStand'', which becomes a post-apocalyptic wasteland in the wake of a disastrous plague, is one of many parallel worlds that exists in the Multiverse. Randall Flagg was trying to conquer that world in the name of the Crimson King, and he wanted to build his own new civilization atop the ashes so that his new subjects could be added to the Crimson King's army.
* ''Franchise/DoctorWhoExpandedUniverse'':
** The ''Literature/DoctorWhoMissingAdventures'' novel ''Venusian Lullaby'' takes a lot of the [[RunningGag throwaway one-liners]] the Third Doctor used to make about his adventures on Venus (that the Venusians sing lullabies, play hopscotch, etc.) and makes a coherent alien race out of them (living about a billion years in the past, when Venus might have been habitable). They're radially symmetrical and move by hopping. Oddly, no mention is made of the oft-referenced "Venusian Aikido" (at least by that name), nor how he might have learned it from such odd creatures.
** The ''Literature/PastDoctorAdventures'' novel ''Divided Loyalties'' establishes that the Doctor was part of a clique in the Prydonian Academy on Gallifrey with the other renegades featured in the original series (the Master, the Monk, the War Chief, the Rani and Drax), Vansell (introduced in the [[AudioPlay/BigFinishDoctorWho Big Finish audio drama]] [[Recap/BigFinishDoctorWho001TheSirensOfTime "The Sirens of Time"]] earlier that year), two new characters (Jelpax and Millenia), and Rallon, who is revealed to have been posessed by the Celestial Toymaker, who used his body in the First Doctor serial by that name.
** ''[[Recap/DoctorWhoNewAdventuresOriginalSin Original Sin]]'' establishes that [[spoiler:Tobias Vaughn from "[[Recap/DoctorWhoS6E3TheInvasion The Invasion]]"]] was responsible for various advanced technologies that plagued the Third Doctor, and also created the glitterguns from "[[Recap/DoctorWhoS12E5RevengeOfTheCybermen Revenge of the Cybermen]]".
** John Peel's Eighth Doctor novel ''War of the Daleks'' does this with the final four Dalek serials of the classic series ([[Recap/DoctorWhoS17E1DestinyOfTheDaleks "Destiny"]], [[Recap/DoctorWhoS21E4ResurrectionOfTheDaleks "Resurrection"]], [[Recap/DoctorWhoS22E6RevelationOfTheDaleks "Revelation"]] and [[Recap/DoctorWhoS25E1RemembranceOfTheDaleks "Remembrance of the Daleks"]]), creating a single overarching plot which was promptly ignored by every ''Who'' writer since.
** ''The Doctor: His Lives and Times'' (a reference book mostly written as an in-universe ScrapbookStory) ties stories together to provide more of a narrative for each Doctor's adventures. Most blatantly, the Seventh Doctor section suggests that [[Recap/DoctorWhoS26E3TheCurseOfFenric Fenric]]'s manipulation wasn't just responsible for "[[Recap/DoctorWhoS24E4Dragonfire Iceworld]] and [[Recap/DoctorWhoS25E3SilverNemesis Nemesis]]", but for almost everything that happened to that incarnation.
* After Creator/IsaacAsimov's extensive CanonWelding of his ''Literature/{{Foundation}}'', Empire and Robots series into one, the final volume of the Second Foundation Trilogy, ''Foundation's Triumph'' by Creator/DavidBrin was a fantastic example of Arc Welding together almost every single book in the series together even better than Asimov had done.
* All 7 other of the ''Literature/IncarnationsOfImmortality'' series, encompassing epic acts by Death, Time, Fate, War, Nature, God and the Devil had this trope. In the last novel in the series, ''Literature/UnderAVelvetCloak'', all of these acts are only minor compared to Nox's (the Incarnation of Night/Secrets) actions (whose actions choose which universes live or die).
* The Larry Niven ''Literature/KnownSpace'' stories develop a bad case of this later on, as the hugely successful ''Literature/{{Ringworld}}'' degenerated into increasingly complex and incomprehensible attempts to produce a Unified Field Theory Of Everything.
* Arthur C. Clarke's ''Rama'' and related sort-of-sequels to ''Literature/TwoThousandOneASpaceOdyssey''.
* ''Literature/LemonySnicketTheUnauthorizedAutobiography'' played this for laughs. Most of the book consists of explaining how everything that had happened up to that point in [[Literature/ASeriesOfUnfortunateEvents the series]] was related to the VFD in various ludicrous ways.
* The first ''Literature/{{Noob}}'' novel did this to some episodes of the [[Series/{{Noob}} original webseries]], making it part of the ''[[FictionalVideoGame Horizon]]'' storyline. When an episode of Season 1 needed to show a character doing FetchQuest (which happened three or four times out of twenty often stand-alone episodes) the QuestGiver always happened to be InTheHood and dressed in BlackCloak, something that could easily be normal for the game and/or due to NoBudget. The first novel, chronologically set after the first season, reveals that [[spoiler: the black cloak is actually a trademark for a group that is after the DismantledMacGuffin central to the first novel; some of the pieces were used as decoration for random objects that they sometimes couldn't go get themselves without attracting attention, hence the fetch quests]].
* ''Literature/SherlockHolmes'': It was revealed, in the first of the two stories by Creator/ArthurConanDoyle to directly feature Moriarty, that the master villain had been involved in several of Holmes' cases before, but had simply never been mentioned until then.
* This sort of thing is quite common in ''Franchise/StarTrekNovelVerse'' books:
** The ''Series/StarTrekTheNextGeneration'' novel ''Q & A'' has every Q-episode of ''TNG'' as being part of a long term plan to [[spoiler: prepare Picard for meeting the beings that sit in judgement over the universe, and convince them it's worth saving]]. Except "Q-Pid". That one he just did for the hell of it. Or possibly for the FoeYay.
** Similarly, the ''Series/StarTrekTheNextGeneration'' novel ''Q-Squared'' implies that almost all the temporal anomalies encountered by Picard and his crew were also the work of Q - and goes on the add a relationship between Q and one-shot villain Trelane from ''Series/StarTrekTheOriginalSeries'' too.
** Peter David is quite fond of this. In ''Vendetta'', the planet-killed from ''The Doomsday Machine'' turns out to have been engineered by a long-dead race as their final revenge against the Borg.
** ''Literature/StarTrekForgedInFire'' ties Sulu's captaincy of the ''Excelsior'' (as seen in ''The Undiscovered Country'' and explored further in ''Literature/StarTrekTheLostEra'') to the Blood Oath plot from the eponymous episode of ''Series/StarTrekDeepSpaceNine''. In other words, Sulu's story arc is now made part of the backstory of Curzon Dax and the Klingon trio of Kor, Kang and Koloth. The novel also ties in the Klingon Forehead arc, from ''Series/StarTrekEnterprise'' and ''Literature/StarTrekVanguard''.
** The ''Literature/StarTrekTyphonPact'' novel ''Paths of Disharmony'' links the ''Literature/StarTrekVanguard'' story arc to those of the ''Literature/StarTrekDeepSpaceNineRelaunch'' and the post-''Literature/StarTrekDestiny'' line, making it all relevant to the current events of the novel.
** A rather pleasing example in the ''Literature/StarTrekVoyagerRelaunch'' with the exploits of Kahless, retroactively linking the novel line's Klingon saga to the relaunch in interesting ways. In ''Literature/StarTrekATimeTo'', Kahless had replaced himself with a hologram (equipped with a mobile emitter) and wandered off to Cygnet IV, supposedly to "do whatever (he) felt like". It was also a test, allowing him to give his usual HurricaneOfAphorisms when the ruse was discovered. In the ''Literature/StarTrekVoyagerRelaunch'', though, it's revealed why he was on Cygnet IV specifically. [[spoiler: The secret headquarters of the qawHaq'hoch are located there, and he's keeping the plates spinning in the plan to keep Miral (B'Elanna and Tom's daughter) safe from the fanatics trying to kill her. Further, the mobile emitter for his holographic replacement was created by B'Elanna herself]].
** Any Christopher L. Bennett novel in the line (''Ex Machina'', ''The Buried Age'', ''Watching The Clock'') is like this. It sometimes borders on ContinuityLockout, but never crosses the line.
** The ''Q Continuum'' trilogy ties together three previously unconnected malevolent energy beings from the original series and movies along with the Galactic Barrier (yes, one of them is "God" from Star Trek V), and as an extension explains why proximity to the barrier resulted in the development of telekinetic powers and personality shift in the original series pilot.
*** We also get a bit of patching for one PlotHole with Star Trek V. The barrier was at the edge of the galaxy in the show, and nigh impossible to get through. In the movie, it was in the ''middle'' of the galaxy and they managed to get in easily enough. Well, it turns out there's two barriers. One is keeping something bad in, the other is keeping something much, MUCH worse ''out.''
* Many ''Franchise/StarWarsLegends'' sources tie in many of [[BigBad Palpatine's]] and especially [[Literature/TheThrawnTrilogy Thrawn's]] actions as being to prepare the galaxy for [[Literature/NewJediOrder the Yuuzhan Vong invasion]]. The degree to which this is accepted by fans varies--it's pretty much considered canon for Thrawn's motivation, but most see Palpatine as just using it as an excuse.
** Jacen Solo's FaceHeelTurn in ''Literature/LegacyOfTheForce'' is seemingly being tied to the BigBad [[EldritchAbomination Abeloth]] in ''Literature/FateOfTheJedi''.
** Another example is Cade Skywalker's unique abilities in ''ComicBook/StarWarsLegacy''. His ability to sense vulnerable fractures has been tied to Mace Windu's sense for more metaphorical "shatterpoints" from [[Literature/{{Shatterpoint}} the book of the same name]], and his ability to heal serious injuries and death using the Dark Side is uncannily close to what Palpatine claimed Darth Plagueis could do in ''Film/RevengeOfTheSith''. And considering that other sources hint that Plagueis created Anakin, it may be connected to that too... [[spoiler: though that was {{Jossed}} in the ''Literature/DarthPlagueis'' novel. Anakin was created as a backlash against Plagueis's machinations.]]
** Back to the subject of Abeloth, the final ''Fate of the Jedi'' novel reveals that she's connected to the Son, the Daughter, and the Father, the living embodiments of the Force first seen in ''WesternAnimation/StarWarsTheCloneWars''.
* Some ''Literature/WarriorCats'' books have melded two subplots together to make their story through use of a retcon.
** ''Crookedstar's Promise'' introduces the Dark Forest to the past and shows it influencing the events of book as early as ''Fire and Ice'' through use of Crookedstar's story.
** ''Yellowfang's Secret'' makes it so that [=SkyClan=] is directly responsible for the rise of Brokenstar, even though they had died out years before his birth.

[[folder:Live-Action TV]]
* Graem Bauer and the "Bluetooth Group" in ''Series/TwentyFour''. The cabal of influential businessmen in the fifth season ordering Christopher Henderson et al. to do their dirty jobs was initially planned to be a shadowy group whose true motives were never explained (and they had no connection whatsoever to Jack or his past). In the sixth season, the previously unnamed head of this group was revealed to "Graem Bauer", and it was explained that he was responsible for most of the government's shady activities going all the way back to the fourth season (when Walt Cummings tried to have Jack killed). Graem is then revealed to be TheManBehindTheMan, as his (and Jack's) father Philip shows up and murders him in his very first appearance.
** Season 7 does it ''again'', revealing the season's BigBad, Alan Wilson, to have been behind even the Bauers' involvement, and the ultimate authority over the Season 5 conspiracy, being head of a [[TheOmniscientCouncilOfVagueness powerful group]] that had been manipulating events for some time and remained at large at the end of the season. Then the storyline [[AbortedArc disappeared without a trace]].
* ''Series/AgentsOfSHIELD'':
** Various, seemingly independent threats throughout Season 1, such as Project Centipede and [[CorruptCorporateExecutive Ian Quinn's]] corporation, are eventually be revealed to all be orchestrated by the same BigBad, [[HiddenVillain the Clairvoyant]] [[spoiler: who turns out to be a HYDRA agent, tying into the events of ''Film/CaptainAmericaTheWinterSoldier''.]]
** One of Season 2's initial main villains, "[[DeadlyDoctor the Doctor]]" [[spoiler: (Calvin Johnson, aka Cal Zabo, aka the comics Mr. Hyde)]] is revealed in the second half of the season to have been working on ([[LoveMakesYouEvil as he perceived it]]) the behalf of [[spoiler: his wife, Jiaying]], who eventually serves as the season's FinalBoss. She, in turn, can blame her StartOfDarkness on [[MadScientist Daniel Whitehall]], the other of the first half of the season's main villains. So, in this way, most of the season's main villains were all connected to each other.
* As part of the showrunners of ''Series/{{Alias}}''' attempts to course-correct after the debacle that was the series' third season, several elements from those episodes, such as Sloane's Omnifam enterprise and seasonal bad guy group The Covenant, were brought back and retconned into being parts of season four BigBad [[spoiler: Elena Derevko]]'s master plan.
* One of the more explicitly identified examples of Arc Welding comes from ''Series/{{Angel}}'''s fourth season, where Skip notes that everything that's happened to Angel and company for a very long time -- Angel's ensouling, Cordelia's ascension, Fred's being trapped in Pylea, Lorne's banishment ''from'' Pylea -- were all part of a GambitRoulette. (It's known that this was all one big {{retcon}} because it wouldn't have worked without Creator/CharismaCarpenter's real-life pregnancy.)
** A smaller version then happened in the next and final season: faced with ExecutiveMeddling to be more episodic without any arcs, after finding out the show would be canceled anyway, Creator/JossWhedon spent the last two episodes revealing that many of the villains over the season were part of a group called the Circle of the Black Thorn, then having the heroes kill them all.
* ''Series/{{Arrow}}'': The first episode of the second season features a group of copycat vigilantes, who among other things kill Starling City's mayor. The midseason finale reveals that they were organized by [[DarkMessiah Brother Blood]] [[spoiler: and [[TheManBehindTheMan Slade]]]], in order to give [[VillainWithGoodPublicity Blood]] the opening he needs to run for mayor.
** Each season also finds a way to tie together its Present Day and Flashback storylines:
*** Season 1 revealed that [[BigBad Malcolm Merlyn]] was responsible for the shipwreck that stranded Oliver on the island to begin with.
*** Season 2's storylines are connected by [[PsychoSerum Mirakuru]]. It was his search for it that led [[EvilutionaryBiologist Dr. Ivo]] to the island in the flashbacks, it's being used as part of Brother Blood's plans in the present, [[spoiler: and it's responsible for Slade's FaceHeelTurn in the flashbacks that leads to him being BigBad in the present]].
*** Season 3's storylines are loosely connected by the presence of Maseo, who was Oliver's ARGUS handler in Hong Kong before his son's death by the Alpha/Omega virus led to him joining the League of Assassins, becoming TheDragon to Ra's Al Ghul in the present. The final episodes tie the storylines more tightly together, however, as [[spoiler: Ra's gets his hands on Alpha/Omega and intends to destroy Starling City with it.]]
*** Season 4's storylines also share only vague connections with each other -- the organization Oliver is sent to infiltrate in the flashbacks is Shadowspire, who serve as VillainOfTheWeek in one episode's present setting and served as part of [[spoiler: Andy Diggle]]'s StartOfDarkness. Also, the [[MacGuffin magic idol]] that flashback villain Baron Reiter is after also serves as [[BigBad Damien Darhk's]] power source in the present.
*** Season 5's storylines have yet another vague connection in that the flashbacks have Oliver being mentored by Talia Al-Ghul, who in the present in now working with new BigBad Prometheus.
** Late in Season 3, Ra's Al Ghul reveals the existence of his rival, Damien Darhk, the leader of H.I.V.E., and that he was responsible for various episodic threats that Team Arrow had faced in Seasons 2 and 3. This on top of H.I.V.E. being responsible for Deadshot becoming a mercenary and the death of Diggle's brother.
* ''Series/BattlestarGalactica2003'' did this extensively in its second half, due to a bad case of Writing by the Seat of Your Pants which stacked up. Creator Ron D. Moore later admitted that despite the show's initial dependence on meticulously plotted storyarcs, he hadn't actually planned out anything for the show beyond the end of the second season (various ideas like "another Battlestar also survived" or "what if they find a habitable planet that isn't Earth"? had been exhausted). The result was that with a bunch of disparate plotlines that he hadn't planned out, he desperately tried to ''retroactively'' weld them all together as related. For example, he admitted he had no idea ''why'' the much-hyped Hybrid child Hera was important, let alone how it related to the rest of the main plots, until he was writing ''the series finale itself''. At the 2009 Paley Center post-finale panel (videos are on youtube of this), you can see Moore give his bizarre self-justification that he is fully capable of ''retroactively'' welding unrelated storyarcs together in a way that works. Needless to say, critics and reviewers were disenchanted as the show wore on.
* ''Series/TheBlacklist'': From the start, it was clear that [[VillainProtagonist Reddington]] only sent the FBI after people on the Blacklist as part of a larger plan, but it's not until the end of season 1, in the two-part "Berlin" episode, that we start to see what that plan is and exactly how the various Blacklisters fit into it.
** "The Director, Conclusion" finally puts together all the hints and pieces of Red's plan throughout the first half of Season 3 to undermine [[NebulousEvilOrganization the Cabal]] enough that he can [[spoiler: exonerate the framed Keen, and take down the Director]].
** "Mr. Gregory Devry" reveals the existence of Shell Island Retreat, a gathering and alliance of the leaders of the world's most powerful criminal organizations. Aside from revealing Reddington himself as a member, several past Blacklisters are mentioned as having been involved before being taken down.
%%%%%* Series/BurnNotice: Anson, Anson, Anson
* ''Series/{{Chuck}}'' welded arcs on top of arcs. About midway through the first season everything that happened up to that point was revealed to largely be the result of a CIA splinter group known as FULCRUM attempting to steal the Intersect. By late in Season 2, Chuck has begun to speculate that many one-shot villains earlier in the first season such as Laszlo were actually connected to the Intersect project and FULCRUM. The Season 2 finale reveals that Fulcrum was part of a larger organization called the Ring. The middle of Season 3 reveals that the Ring's direct involvement goes back much further, and that another one-shot villain from Season 2 was actually working for them. When Season 4 rolls around, you learn that yet another one-shot villain from Season 2 was actually working for new series big bad Volkoff Industries, and that the entire history of the Intersect project itself was directly connected to Volkoff himself. Finally in Season 5 you learn that rogue CIA agent Quinn was quite literally behind EVERYTHING--Fulcrum, the Ring, and Volkoff Industries--out of his desire to get revenge on Chuck for "stealing" the Intersect from him.
* ''Series/TheDefenders2017'' bridges together the two different plot lines involving [[AncientConspiracy the Hand]] introduced in previous series. In ''Series/{{Daredevil|2015}}'', they're established as being in a SecretWar with [[AncientTradition the Chaste]], while in ''Series/IronFist2017'', they're stated to be ancient enemies of [[HiddenElfVillage K'un L'un]]. Here it's revealed that the Hand was founded by exiles from K'un L'un, and the Chaste was created afterwards to serve as the Iron Fist's army to fight them in defense of the city.
* ''Series/DoctorWho'':
** There was a bit of Arc Welding near the end of its original run, when Ace's involvement with the Doctor between [[Recap/DoctorWhoS24E4Dragonfire "Dragonfire"]] and [[Recap/DoctorWhoS26E3TheCurseOfFenric "The Curse of Fenric"]] (eight multi-part stories over three seasons by that point) was revealed to be part of Fenric's BatmanGambit to trap the Doctor (moral of the story: don't try a BatmanGambit against a {{Chessmaster}}). It also provided a [[HilariousInHindsight bit of disappointment]] for Classic Who fans when the series returned and [[ArcWords "Bad Wolf"]] turned out not to be a returned Fenric.
** Between the Classic and revival series, the Time War, a cataclysmic war between the Daleks and the Time Lords, annihilated both races for good with the exception of the Doctor. The series eventually connects this event to the Fourth Doctor story [[Recap/DoctorWhoS12E4GenesisOfTheDaleks "Genesis of the Daleks"]], where the Doctor attempted a genocide of the species but failed (which has no serious effects on the Classic series's overarching plot save for [[HijackedByGanon introducing Davros]]) -- reimagining the event as the Time Lords firing the first shot in the war.
** In Series 5 of the new series, the startling lack of historical commentary about a big freaking [[Recap/DoctorWhoS30E14TheNextDoctor Cyberking]] stomping around Victorian London is retconned to have been another casualty of the cracks in time.
** [[Recap/DoctorWho2013CSTheTimeOfTheDoctor "The Time of the Doctor"]], the Eleventh Doctor's GrandFinale, concludes virtually all major ongoing plots (the cracks in time, the explosion of the TARDIS, the First Question, etc.) by tying them into the Ninth and Tenth Doctor Time War MythArc.
** In Clara's first appearance in Series 7, [[Recap/DoctorWhoS33E6TheBellsOfSaintJohn "The Bells of Saint John"]], she offhandedly mentions she got the TARDIS phone number from a woman in a shop who told her it was a help line. Flashforward to the Series 8 premiere, [[Recap/DoctorWhoS34E1DeepBreath "Deep Breath"]], where a mysterious ad in a paper reunites Clara and the recently regenerated Twelfth Doctor, after which he brings up the phone incident again, pointing out that someone seems to want them together. Flashforward again to the season finale, [[Recap/DoctorWhoS34E12DeathInHeaven "Death in Heaven"]], where it's revealed that that woman was [[BigBad Missy]], who brought Clara and the Doctor together as part of her larger overall scheme against the Doctor.
* A similar event occurred in ''Series/{{Firefly}}'', another Creator/JossWhedon show. Although the Reavers and River's torture at the hands of the Alliance are introduced in the pilot episode, the ''Film/{{Serenity}}'' movie later ret-cons them to being linked together. Now, instead of being a group of bloodthirsty savages as a parallel to the American Indians depicted in pulp Westerns, they are analagous to the Infected from ''Film/TwentyEightDaysLater'', and the reason that River is being so strongly hunted by the Alliance is that she knows secrets like this.
* ''Series/KaizokuSentaiGokaiger'' episode 40, which not only turns the Gokaigers' EarlyBirdCameo (a BigLippedAlligatorMoment during the ''[[Series/TensouSentaiGoseiger Goseiger]]''/''[[Series/SamuraiSentaiShinkenger Shinkenger]]'' ReunionShow) a canon event, but also ties into the team's quest of GottaCatchThemAll.
* In the old ''Series/KamenRider'' series, many an evil organization was ruled by a guy called the "[insert this year's evil organization name] Great Leader," always voiced by veteran voice actor Creator/GoroNaya. Welding comes in with the later seasons having the new [Organization] Great Leader often say "oh, yeah, I was behind them all, and those ''other'' organizations from the last couple of series I ''wasn't'' in too!" Not only were all of Naya's "Great Leaders" made one character, with the final enemy of ''Black RX'' voiced by Naya as well, it's theorized that ''every pre-hiatus Kamen Rider villain ever'' is either the Great leader himself or one of his pawns.
** As for the modern era, he appears in teamups now and again, first voiced by Naya up until his death, and then replaced by Creator/TomokazuSeki, though he doesn't take credit for seasons he wasn't in. However, the NonSerialMovie of ''Faiz'' gave the BigBad three ManBehindTheMan figures, one being played by Naya. This in a series that also has people being turned into monsters. Though far from canon, there's a real case to be made for the Great Leader being behind that series.
** The more recent series have Foundation X playing the same part: ''Double, OOO'' and ''Fourze'' all had them involved behind the scenes. The "Foundation X Trilogy" culminated in a film where they're finally the BigBad instead of just ''behind'' the BigBad... but the film's villain Lem Kannagi was a rogue member and his defeat was no setback to the organization. They're perfectly capable of saying "Oh, did you think [insert your favorite new villain here] did it alone?" about any series after them (except ''[[CosmicHorrorStory Gaim]]'', perhaps.) On top of ''that,'' Kannagi's final form was a similarly-named homage to that of an old-school villain, and who were all the old-school villains created by, again?
* A great many of the episodes of the revival of ''[[Series/TheOuterLimits1995 The Outer Limits]]'' are retroactively revealed to take place in the same continuity. Unfortunately for continuity, several of those episodes are entirely contradictory. Some of them, however, are stated as taking place in {{Alternate Timeline}}s.
* ''Franchise/PowerRangers'' had two major examples of this:
** ''Series/PowerRangersInSpace'' revealed that [[BigBad Dark Specter]] was behind everything that happened in the series to that point. Combining the narratives of all the previous seasons ([[Series/MightyMorphinPowerRangers Mighty Morphin]], [[Series/PowerRangersZeo Zeo]], [[Series/PowerRangersTurbo Turbo]], and In Space) into one greater arc.
** In ''Series/PowerRangersNinjaStorm'' it is revealed that each plot by the BigBad Lothor was actually part of a very smart BatmanGambit.
* At the end of the first season of ''Series/TheSopranos'', Big Pussy has vanished. [[TitleDrop No one knows anything]]. The writers of the show were just going to let it go at that--people do, indeed, vanish with no explanation, though it's rare. However, when they heard how the fans were wondering what happened to him, they welded Pussy into the story of Jimmy's being TheMole, with him being a second one.
* ''Franchise/StarTrek'': ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'' does excellent examples of {{Story Arc}}s and also of Arc Welding. Starting in mid-season 2 and possibly earlier, the seeds are planted in an almost offhanded manner for the coming storyline. Then, at the end of season 2, it's all revealed to be part of a big plot that isn't concluded until the final episode of the final season -- which itself is the finale of a 9-part arc within the MythArc of the show.
** Also, ExecutiveMeddling resulted in the Klingons returning to their [[Series/StarTrekTheOriginalSeries Kirk-era]] level of villainy just as the Dominion was planned to take center stage. ThePowersThatBe did the best they could, and made it fit at the end by making Changeling manipulation responsible.
* ''Series/{{Stella|US}}'' used [[YouLookFamiliar one frequent actor]] to set up an arc for the series.
* Arc Patching, if not Arc Welding, was done in ''Series/VeronicaMars'', when the season 2 bus bombing storyline wrapped up. The perpetrator was revealed to also have raped Veronica at Shelly Pomroy's party, a storyline thought to be wrapped up in season 1 as being not rape, but mutually drugged-up semi-consensual sex. This explained Veronica's chlamydia, despite her having only two (or, as TheReveal made plain, actually three) sexual partners and presumably using protection, the existence of which was used to paint Veronica as a slut and therefore untrustworthy in the trial of Aaron Echolls. The blatant illegality of delving into her medical records for some reason ''not'' resulting in a mistrial is another debate entirely.
* ''Series/{{Whitechapel}}'' did this in its fourth season. Up until this point, the team had dealt with unrelated cases, but the fourth season not only introduces the existence of the supernatural, but posits that all the grisly crimes in Whitechapel are the work of a "provocateur" who goads all the murderers into committing their crimes.
* ''Series/TheXFiles'' did this in later seasons, with dormant alien DNA supposedly accounting for much of the apparently Earthbound paranormal activity Mulder and Scully investigated.

* One of the few examples (perhaps the only one, seeing as concept albums are nowhere near as common as normal albums) occurring in Music: Music/BetweenTheBuriedAndMe do this with their Parallax storyline when it's revealed that Prospect 2 was [[spoiler:the adult male that talked too much in "Lost Perfection", and that he was one of the three lovers of the woman in "Prequel to the Sequel".]]
* Music/MarilynManson's ''Antichrist Superstar'' and ''Mechanical Animals'' were originally thought of as two separate concept albums, as they have different protagonists, plots, and points, plus the entire universe is destroyed at the end of ''Antichrist Superstar''. With ''Holy Wood'' however, the Triptych was revealed, and the plot flows in reverse, from ''Holy Wood'' to ''Mechanical Animals'' to ''Antichrist Superstar''. The protagonist of ''Holy Wood'', Adam Kadmon, the first to rebel against Holy Wood, is the father of The Worm/Antichrist Superstar from, well, guess. Coma (who in the novel, only Chapter 10 of which was ever released, is the daughter of the leader of Holy Wood), is his mother, who after the suicide of Adam Kadmon, falls into rampant drug use and then the aliens Alpha and Omēga fall in love with her. When she herself dies in the song "Coma White", both lose hope, and the song "Irresponsible Hate Anthem", from ''Antichrist Superstar'', is actually performed by Omēga, not The Worm, as proven by the three "live songs". The liner notes for ''Antichrist Superstar'' show that "Irresponsible Hate Anthem" was recorded live on Valentine's Day, 1997. However, the album came out in 1996. The liner notes again say this about "I Want To Disappear" off of ''Mechanical Animals'', an album that came out in 1998, and the song was in fact not actually played at the real Valentine's Day, 1997 show. Finally, "Born Again" off of ''Holy Wood'' is also said to have been recorded on the same day. This song also was not played live, especially seeing as the album it's from came out in 2000. The albums tell the story of three characters. ''Holy Wood's'' Adam Kadmon fights the system, only to get brought into it and ultimately kill himself. ''Mechanical Animals''' Alpha and Omēga [[ShoutOut are space]] [[Music/DavidBowie alien rock stars]], who crashed and were captured and enslaved. Alpha sings the emotional songs on the album, Omēga the vapid, drug songs, however turns against the system due to the death of Coma. The Worm, Adam and Coma's son, idolizes Omēga, and leads his own revolution against the system and wins, only to turn against his mindless, obsessive fans who worship him as a god, and in his rage becomes the Antichrist Superstar and destroys the universe, thus ending the Triptych.

[[folder:Tabletop Games]]
* Up until the Invasion block of ''TabletopGame/MagicTheGathering'', the storylines of the sets before were mostly WorldBuilding the plane of Dominaria. Then came the story revision, the Weatherlight set, and the Tempest block, which set up an ongoing storyline over the next twelve or so sets that would drastically change the way the game told stories, as well as cobble together all the previous sets into a sort of long-term storyline, which the arc would then deal with. It all came to a head in the Invasion block with the BigBad and his cronies from the previous stories converging on Dominaria to overlay the artificial plane of Rath (introduced in the Tempest bllock) and give the Phyrexians (introduced back in Antiquities, the second-ever set) a new world to ravage.
** Also, the problems that were dealt with in the Time Spiral block were said to have done things which were major in other blocks, like making the Emperor insane, which convinced him to steal a baby kami, which resulted in the Kami War which made up the Kamigawa block.
* The creators of the [[TabletopGame/DungeonsAndDragons D&D]] setting ''TabletopGame/{{Ravenloft}}'' retroactively Arc Welded its first six adventures together into the Grand Conjunction story arc, using a Vistani prophecy as solder.
* Arguably, the [[TabletopGame/DungeonsAndDragons D&D]] settings ''TabletopGame/{{Planescape}}'' and ''TabletopGame/{{Spelljammer}}'', both of which were specifically created to allow the numerous other settings of D&D to mix with each other.

[[folder:Video Games]]
* ''VideoGame/MetalGearSolid'' was mostly self-contained, despite being a sequel to the MSX games ''[[VideoGame/MetalGear1 Metal Gear]]'' and ''VideoGame/MetalGear2SolidSnake''. ''VideoGame/MetalGearSolid2SonsOfLiberty'' introduced [[AncientConspiracy The Patriots]], whose operatives were largely responsible for the events in the series. ''VideoGame/MetalGearSolid3SnakeEater'''s place in the Patriots arc is [[spoiler: their origin story (as evident by the password Zero instructs Snake to use when he meets ADAM),]] but it's missed by many until ''VideoGame/MetalGearSolid4GunsOfThePatriots'' spells it out because the Patriots as they exist by the time ''Sons of Liberty'' takes place are [[AIIsACrapshoot very, very different]] than the organization used to be.
* In ''VideoGame/GuildWars Nightfall'', it's revealed that servants of Abaddon were responsible for driving the Charr into human lands in Tyria, leading to all the major background events of the ''Prophecies'' campaign; another servant led to the downfall of Shiro Tagachi, the BigBad of ''Factions''.
* The VideoGame/ChzoMythos tetralogy of games feature this; ''5 Days a Stranger'' was originally a stand-alone game, as was its distant sequel, but the later titles tie them together to form an encompassing story arc. Appropriately, the major threat of the first two games (and an important story character in the other two) is an insane killer referred to as 'The Welder' because of the mask he wears.
* "Evolution requires sacrifice." Spoken by [[spoiler:Lumine]] of ''VideoGame/MegaManX8'', and Serpent of ''VideoGame/MegaManZX''. This refers to the evolution of the [[RidiculouslyHumanRobots Reploids]] into something else...Granted, those two are in a future (and a world) that ''anything's'' possible with the Reploids (or technology in general). And then, in the VideoGameRemake (and possibly ContinuityReboot) ''VideoGame/MegaManMaverickHunterX'', Sigma begins spreading these beliefs himself. [[WhatCouldHaveBeen If the reboot series wasn't axed]], the developers could have elaborated on the concept even more.
** Meanwhile, in ''VideoGame/MegaManZero'', unlike the [[VideoGame/MegaManClassic two]] [[VideoGame/MegaManX series]] that preceded it, there is a different BigBad for the first two games. Then, that novelty just had to be shot down by ''Zero 3'', wherein ''that'' game's BigBad, Dr. Weil, can be easily marked responsible for the events of the previous two, legibly making him the BigBad for the '''entire''' ''Zero'' series.
** Wily claims to have orchestrated ''VideoGame/MegaManBattleNetwork 2'' at the end of ''Battle Network 3,'' making the first three games one saga about Wily's plots to destroy the Internet (really) culminating with the Alpha plan in ''3''.
* VideoGame/KingsQuest: Dahlia, Hagatha, Mannanan, and Lolotte all appeared to be generic evil wizards and wicked witches. But then, we hear that the BigBad in VideoGame/KingsQuestV is the "brother" of Hagatha and Mannanan and looking for revenge. Then VideoGame/KingsQuestVI has a single, damning letter alluding to the "Brotherhood of the [[LegionOfDoom Black]] [[TheOrder Cloak]]," who address one another as "brother" and "sister." The letter implicates ''at least three'' of the series villains as members... and could possibly implicate ''all of them'' as members. OhCrap {{Fanon}}, especially the FanSequel and FanRemake games will ''cheerfully'' run with this theory.
* For almost 20 years, ''[[VideoGame/SonicTheHedgehogCD Sonic CD]]'' was a GaidenGame with no set place in the series' timeline (Due to the lack of Tails or Super Sonic and the fact it was meant to be ''[[VideoGame/SonicTheHedgehog2 Sonic 2]]'', most fans just assumed it was a prequel). However, as of the new remake for X-Box Live, Playstation Network, and iPhones, features were added suggesting (and WordOfGod asserted) that it actually occurred sometime before ''[[VideoGame/SonicTheHedgehog4 Sonic 4]]'', and it's specifically tied to Episode II.
* The four DownloadableContent packs of ''Videogame/FalloutNewVegas'' are part of a bigger storyline which lead to the confrontation of the player-character, The Courier with Ulysses, TheRival.
* ''VideoGame/SuperRobotWars'' is a MassiveMultiplayerCrossover series of HumongousMecha shows. Many games often do this by drawing on similarities between different series to weave common bonds.
** The biggest example occurred in the first ''VideoGame/SuperRobotWarsAlpha'' game. The BigBad has an ''extremely'' long sequence [[MotiveRant where he explains how]] [[TheManBehindTheMan he was behind everything in every series]] that was in crossed over in the game. This created a [[MemeticMutation meme]] in the Japanese fanbase where the villain claims responsibility for just about everything. Then in the second ''VideoGame/SuperRobotWarsOriginalGeneration'' game, the BigBad of ''Alpha'' reappeared and made ''another'' long speech about how he was behind everything. It's fully AscendedMeme.
** VideoGame/SuperRobotWarsUX
*** By the way, [[Anime/MazinkaiserSKL the island covered by the gravity curtain was apparently a research center]] for gravity engine cores since World War II (a key plot point to ''The Wings of Rean'').
*** Linebarrel is connected to Demonbane because the latter is also a "[[AMechByAnyOtherName Machina]]" and the [[Manga/LinebarrelsOfIron Katou Organization]] are hunting them down. More specifically, Linebarrel and Demonbane are known as "Deus Ex Machina". Both stories' time loop events are interconnected in ''UX''.
*** [[Anime/FafnerInTheAzureDeadAggressor Tatsumiya Island]] is a part of the [[Anime/MobileSuitGundamSEEDDestiny Orb Union]].
*** Considering the whole Machina idea or rather the meaning behind it is machine god. Linebarrel's Juda seems central to the whole idea of gathering Demonbane, SD Gundam, Machina, Fei-Yen HD and even partially Heroman as a collection of possible Machinas, though obviously not all of them have the idea of a Machina god behind them or rather behind their respective series like Linebarrel and Demonbane do. This would be a reason for Juda and a way to tie in a lot of the story together.
*** Scenario 24 is a mash of the starting battle from ''Sayonara no Tsubassa'' as well as the titular impact of Trailblazer, by mixing in the fact that the Galaxy refugee ships were at Jupiter. Fighting Vajra ships for the first time is only a tease to the real first appearance of the ELS. This also gives the chance for more interactions between Alto and Setsuna, and the final save coming from Tieria in the Raphael.
*** Fei-Yen's plot is tied in with Mazinkaiser SKL, where it is the robot used by the female kingdom. She starts out really reserved, then once you go on SKL/Macross route split she has an encounter with Miku[[labelnote:*]]Note that in game she never mention Miku's name[[/labelnote]] and gets her KYUNKYUN beam, then during SKL finale she goes super mode[[labelnote:*]]which is basically Fei-Yen's original SuperMode[[/labelnote]] when Kiba shows up, and during Fafner TV finale, she gets her Morale boosting special command. [[spoiler:''In the Blue Sky'' and ''Operation Azure''. Sink it for a moment.]]
*** The Tokyo in the interior of the moon, which is from where all the Humanoid Machinas stem from, is also strikingly similar to Shou's Tokyo. Shou and the Dunbine characters are [[spoiler:basically from a previous incarnation of the world]]. [[spoiler:Later on we find out Juda's "view of future" is actually about what happened ''before'', so at least part of the cast are also of the same origin.]]
** ''VideoGame/SuperRobotWarsV'':
*** ''[[Anime/ShinMazinger Mazinger Edition Z: The Impact!]]'' never got a second season, and consequently never went into the ''Great Mazinger'' storyline despite some foreshadowing. As such, ''Shin Mazinger Zero vs The Great General of Darkness'' is brought in to give ''Great'' some proper representation.
*** The timeline of ''Anime/SpaceBattleshipYamato2199'' and [[MobileSuitCrossboneGundam late UC]] is referred to as the NCC, or New Correct Century, as if it were a singular Gundam timeline, 100 years after the events of ''[[Anime/MobileSuitGundamCharsCounterattack Char's Counterattack]].''
*** [[Anime/CrossAnge Draconium]] is derived from the [[Manga/GetterRobo Getter Rays]] and since the Dragons are humans who evolved into Dragons to purify the land from the radiation, they can temporarily make the Shin Getter weaker.
*** [[Anime/Gundam00AWakeningOfTheTrailblazer Aeolia]] is also another member of the [[Anime/CrossAnge Ancient People]] who seeks to overthrow Embryo.
*** [[Anime/MartianSuccessorNadesico Ruri]] is another successful [[Anime/MobileSuitGundamSeed Ultimate Coordinator]].
*** [[spoiler:[[Anime/TheBraveExpressMightGaine Black Noir]] manipulated Embryo, the events involving the male protagonists from the AD Dimension, and a couple other things just to enjoy as a game. When Aeolia learned of Black Noir, the former created Veda as a countermeasure.]]
*** Much of the plot of ''[[Manga/GetterRobo Getter Robo Armageddon]]'' is folded into the plot of ''ShinMazinger'', such as Great Mazinger and Mazin Emperor G being powered by both getter rays and photonic energy and [[spoiler: Kenzo Kabuto constructing the Shin Getter Dragon.]]
*** [[Anime/Daitarn3 Banjo Haran]] was raised on Mars, meaning he's an [[Anime/MartianSuccessorNadesico A-Class Jumper and thus capable of Boson Jumping.]]
** ''VideoGame/SuperRobotWarsX''
*** "[[Anime/MashinHeroWataruSeries Soukaizan]]," "[[Anime/TengenToppaGurrenLagann The Country of Beasts]] (Kamina City included)," and "[[Anime/CrossAnge The Country of Mana]]" makes the world of Al-Warth.
*** [[Anime/MashinHeroWataruSeries Wataru]]ís own world of Japan is the same as ''Anime/TheBraveExpressMightGaine'', and the ''Anime/ShinMazinger'' series. With Wataru living in Nouvelle Tokyo City, and himself being friends with [[Anime/TheBraveExpressMightGaine Tetsuya Yoshinaga]].
*** Shou Zama is an Area 11 citizen, while Todd Guiness and Marvel Frozen are Brittanians. Also, ''Gundam Wing'', ''Dunbine'', and ''Code Geass'' are part of the same world.
* ''VideoGame/PokemonMysteryDungeonExplorers'' had few [[StoryArc story arcs]] in the first place, but near the end of the game, you find out that [[spoiler: Darkrai was responsible for both [[MadGod Primal Dialga]] and Palkia trying to [[FateWorseThanDeath remove you from time and space respectively.]]]]
* ''VideoGame/StarTrekOnline'' has a number of Arc Welding as it takes everything it can from the TV series, movies, and other sources. Among those:
** Miral Paris' role as the Klingon Messiah is tied into how the Klingons regain their ridged foreheads between the original series and ''Film/StarTrekTheMotionPicture''.
** Near the end of ''Series/StarTrekDeepSpaceNine'', a group of Dominion ships is threatening to invade the titular [=DS9=] by way of the Bajorian wormhole when suddenly they just disappear! [[spoiler:They return in the Featured Episode series "The 2800"]].
** Probably the biggest one? The game's true BigBad? [[spoiler: The ''Iconians'', a group of not-so-extinct race that had ruled the galaxy thousands of years ago whose technology had been a real thorn in Picard and Sisko's sides when they encountered them in ''Series/StarTrekTheNextGeneration'' and ''Series/StarTrekDeepSpaceNine''. Even worse, it's ''them'' who had helped caused the destruction of Romulus and Remus in the backstory to ''Film/StarTrek (2009)''!]]
** The Foundry, in turn, has been known to pull this on the canon game, especially with the very episodic and frequently disconnected Federation missions. A prime example is the mission "[[Recap/StarTrekOnlineFoundryDivideUtRegnes Divide ut Regnes]]", which in the process of {{fix|Fic}}ing the much-maligned [[ThatOneLevel "Divide et Impera"]] finds time to retroactively explain two aspects of the mission "Preemptive Strike": why the Romulans are preparing to attack the Federation[[labelnote:*]]They're retaliating for your time-traveling starship hitting one of their facilities to capture an Undine infiltrator and killing everybody (or so they think; it was the Undine who actually did the killing but they have no way of knowing).[[/labelnote]], and how Admiral T'nae knew about it[[labelnote:*]]Your time-traveling future self told her.[[/labelnote]].
* The first four games in ''Franchise/TheElderScrolls'' series consist of [[NonLinearSequel largely unconnected stories]] set in the same world. However, the fifth game of the main series, ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'', does some Arc Welding which connects the overall stories in its main quest. Specifically, the destruction or removal of a various {{Cosmic Keystone}}s and [[TheTower metaphysical "Towers"]] in the previous games herald the return of Alduin, the BigBad BeastOfTheApocalypse who was [[SealedEvilInACan cast out of the stream of time]] in the past but prophesied to return.
* The ''Creator/ArtixEntertainment'' writers are so guilty of this trope it's not even funny. The most obvious example is their first and flagship game, ''VideoGame/AdventureQuest'', which got so bad with this during the Devourer Saga that it was next to impossible for the userbase to keep track of who was responsible for what, or how X arc was supposed to fit into the wider Saga. The spin-off games are a lot better about this, but there's still some welding here and there that can cause crossed eyes.
* Most ''Franchise/{{Kirby}}'' games, while sometimes direct sequels to one another, are usually episodic. Around ''VideoGame/KirbysReturnToDreamLand'', however, past games began to tie in more explicitly to newer ones, with Magolor mentioning how the ancients who built the Lor Starcutter made "clockwork stars" (implying a connection to ''VideoGame/KirbySuperStar''[='=]s NOVA), the [[spoiler:Dimension Mirror from ''VideoGame/KirbyAndTheAmazingMirror'']] being the cause of [[spoiler:Queen Sectonia's [[GodSaveUsFromTheQueen tyrannical personality]]]] in ''VideoGame/KirbyTripleDeluxe'', ''VideoGame/KirbyPlanetRobobot''[='=]s FinalBoss [[spoiler:bearing a strong resemblance to NOVA, even having wish-granting powers and a similar HeartDrive that's fought as a boss]], and ''VideoGame/KirbyStarAllies'' making implied connections between the game's antagonists and [[spoiler:Dark Matter from the so-called "[[VideoGame/KirbysDreamland2 Dark]] [[VideoGame/KirbysDreamland3 Matter]] [[VideoGame/Kirby64TheCrystalShards Trilogy]]", due to Hyness' MotiveRant and Void Termina's final form]].
* When it was originally released, the whole ''VideoGame/MetroidPrimeTrilogy'' (despite the ''Prime'' name becoming the primary moniker for mainline 3D ''Franchise/{{Metroid}}'' games) was considered to be a series of {{Gaiden Game}}s storywise, not having any effect on the series' primary MythArc involving the war against Mother Brain and the Metroids. This was due to the games not having the involvement of series co-creator Yoshio Sakamoto; indeed, the widely derided ''[[VideoGame/MetroidOtherM Other M]]'', which did have Sakamoto's involvement, created many [[ContinuitySnarl continuity errors]] with the ''Prime'' series due to the game's writing not taking the latter into account. It wasn't until ''[[VideoGame/MetroidSamusReturns Samus Returns]]'', a remake of ''[[VideoGame/MetroidIIReturnOfSamus Return of Samus]]'', when the ''Prime'' series was finally connected with the "primary" arc, [[spoiler:where newly added FinalBoss Ridley is shown to have partially regenerated his organic body after his time as the {{Cyborg}} Meta Ridley in the ''Prime'' trilogy.]]

[[folder:Visual Novels]]
* ''VisualNovel/AceAttorneyInvestigationsMilesEdgeworth'':
** In both games, [[spoiler:the first four seemingly unrelated cases turn out to have all been part of the BigBad's BatmanGambit. In fact, the main point of the final case is for the player to figure it out. It is, however, subtly foreshadowed from the beginning, and the hints are there if you look for them.]]
** In the second game, [[spoiler:the Berry Big Circus (focal point of ''the'' most base-breaking case in the series, "Turnabout Big Top") winds up being the place of employment and unwitting facilitator of several plans of that game's BigBad]]. Considering most of the references to non-Investigations games being little more than TheCameo, this one stands out. Meanwhile, ''2'' also ties in the main arc of the first game to an even ''greater'' scale, [[spoiler:due to the Inherited Turnabout prominently featuring playable segments as ''the'' [[PosthumousCharacter Gregory]] [[CrusadingLawyer Edgeworth]] during his ultimately-fatal last case. Due to tying it in with the ''Investigations'' games' MythArc, the events behind his final case against [[AmoralAttorney Manfred von Karma]] are given even ''more'' significance in the grand scheme of things.]]
* Despite ''Visualnovel/NineHoursNinePersonsNineDoors'' feeling like a self contained story, its sequel ''Visualnovel/VirtuesLastReward'' manages to very successfully connect it to that game's myth arc (and by extension the overall plot of the eventual trilogy) by revealing that [[spoiler:Gentarou Hongou, aka Ace, was a member of Free the Soul, and that Cradle Pharmaceutical and his experiments with the morphogenetic field were funded by the cult. The symbol on the robes Snake was forced to wear in 999 is also used as Free the Soul's coat of arms.]]

[[folder:Web Comics]]
* ''Webcomic/ItsWalky''[=/=]''Roomies''[=/=]''Joyce and Walky''. The entire storyline consists of retconning arcs to weld them into bigger arcs reaching further into the past, culminating in a gigantic "conclusion" arc connecting every character that ever appeared in the comic into a huge overarching plot (whose final resolution ends the comic).
* ''Webcomic/DominicDeegan'': It turns out [[spoiler: the King of Callan, who wants humanity/himself to control the source of magic (which is apparently a comet) so badly he tried to ''destroy an entire country and wipe out its people'' when it was their "turn" use it]] was responsible for just about every catastrophe in the comic.

[[folder:Web Original]]
* [[ SCP-2000]] double-checks the welding around the Wiki/SCPFoundation. Officially it's all been linked for several real-life years, but in practice it's a massively disparate collection of collaborative stories on a wiki with an extremely loose version of "canon".

[[folder:Western Animation]]
* Various jokes and gags made in the purely episodic first season of ''WesterAnimation/AdventureTime'' either return in later seasons to add to the show's overall MythArc, or are re-contextualized to bring more insight into a character. One of the most notable examples of this is the season four episode "I Remember You", which uses an early throwaway gag of Marceline constantly moving all over the Land of Ooo, and explains that the main reason for this being her constantly running from her now mentally-insane father figure, the Ice King, who took care of her during the nuclear apocalypse but can no longer remember the bond they once shared.
* Parodied in ''WesternAnimation/CloneHigh'''s final episode, where the [[TheOmniscientCouncilOfVagueness Shadowy Board of Directors]] bring together literally every one-shot guest character or celebrity and address them as collaborators. Of course, this was mostly just so the episode could end with [[spoiler:''literally every character ever to appear on the show'' -- except Scudworth -- frozen inside a meat locker.]]
%%* This happens with ''WesternAnimation/CodenameKidsNextDoor'' in its first season. It turns out that Father was behind a lot of the episodes.
* The ''WesternAnimation/{{Futurama}}'' episode "The Why of Fry" reveals that Fry coming to the future was part of a wider conspiracy, as his lack of delta brain wave made him the only person who could save the Universe from the Brainspawn. Whilst at least part of this was planned from the beginning of the show, the events of "Roswell That Ends Well" (where Fry becomes his own grandfather) were used as an explanation for the lack of brain wave, which was not part of the original plan.
* ''WesternAnimation/{{Gargoyles}}'':
** Most of the middle part of season 2 was already an arc, but then, during the two-part episode "The Gathering", where you see Oberon's Children filing into his castle to be recognized by him back on Avalon--and you realize they're familiar to you. Odin, Anansi, Banshee, Coyote, even Anubis are all his subjects. How powerful, then, must Oberon be? This was already a StoryArc of sorts--though Angela's, Goliath's, and Elisa's adventures were episodic, they were already linked by their method of travel--but now you see it was all part of a second arc as well, to set up the StoryArc finale.
** Also, many unrelated aspects of the first half of the series were ultimately revealed as part of [[EvilSorcerer the Archmage's]] far-reaching BatmanGambit for world domination.
* Used not in ''WesternAnimation/GravityFalls'', but in the show's credits. At the end of each episode, there's a coded message in the credits. Despite their secretive nature, however, the messages are very simple and mostly just are cheap jokes. After Season 1 ends though, Dipper's Guide to the Unexplained comes out, and each short ends with a piece of a secret message that has to be decoded by looking through the season's credits messages. This message was obviously formed after the fact, but allowed for the credits' messages to have actual significance among speculating fans.
** WordOfGod confirms that the first season's MonsterOfTheWeek approach to episodes were mostly because of Disney not knowing if a mystery show would sit well with audiences. After gaining significant popularity, the show was arc-welded with a conclusive first season ending, that led to a more cohesive StoryArc in season 2.
* Interviews with the creative team behind ''WesternAnimation/JusticeLeagueUnlimited'' and their remarks in various DVD audio commentaries reveal that they were several episodes into the production of ''Unlimited'' before they realized that they were working toward what became the "Cadmus Arc." The majority of the arc expanded upon and revolved around the events of "A Better World," an episode from season two of ''Justice League'' which had been written with no thought to an ongoing story. The ultimate reveal of the BigBad, Brainiac, actually connected back to an episode of ''WesternAnimation/SupermanTheAnimatedSeries'', which had been produced eight years and two TV series before the current series was even conceived. There were also throw-away lines and references that connected to as far back as "On Leather Wings", an episode of ''WesternAnimation/BatmanTheAnimatedSeries'' that was the ''very first'' entry in the Franchise/{{DCAU}}.
* ''WesternAnimation/TheLegendOfKorra'': "The Stakeout" reveals that [[spoiler:Unalaq, the BigBad of Book 2, was a member of the Red Lotus, the villains of Book 3, and he helped them kidnap Korra. However, he did betray them, and his plan to become a Dark Avatar was not the Red Lotus's plan.]]
* The ''WesternAnimation/SouthPark'' episodes "200" and "201" begin as a follow-up to "Trapped in the Closet" and then tie together the plots in "Mecha-Streisand," "Ginger Kids," "Scott Tenorman Must Die," "The Super Best Friends," "Butt Out," "Fat Butt and Pancake Head," the "Cartoon Wars" two-parter, and "Cartman's Mom Is Still a Dirty Slut," and this does not include the numerous previously one-shot characters who make another appearance in this two-parter.
* The ''WesternAnimation/StrokerAndHoop'' finale has them kidnapped along with Double Wide and put inside K.A.R.R over a canyon while being taunted by their kidnapper who gives them three guesses on who he is lest he drops them in the canyon. Through the whole episode the three call back recent episodes and go over suspects. [[spoiler: Its eventually revealed to be a no name background character whose appearance changed in each encounter with the duo save for his voice.]]
* ''WesternAnimation/TransformersAnimated'' had Ratchet's war flashbacks; in "Thrill of the Hunt" he flashes back to serving alongside Arcee, and in "A Bridge Too Close" he recalls having served in the war with Omega Supreme, [[spoiler:also the Autobots' ship]], as an old friend. The third season reveals that [[spoiler:Arcee's role as intelligence officer during the war had actually been to carry the activation codes necessary to implement Omega Supreme, an experimental weapon.]]