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For almost a full season, the plucky folks who help those in need have defeated Monster of the Week after Monster of the Week, 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 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 form of Continuity Creep that occurs when a series which has heretofore been episodic retcons itself so that it's all linked in a Story Arc. The most common approach to Arc Welding is when an antagonist, hidden up to that point, is shown to be responsible for all the major threats the protagonists have faced thus far.

Alternatively, several seemingly disconnected arcs might be revealed to part of a larger Myth Arc. This is rarer, possibly because it's harder to do well, and any works that attempt it may risk being cancelled before they can make the big reveal or retcon.

Arc welding is different from Story Arc or Myth Arc because it is always retroactive; or, at the very least, the work doesn't make it clear that there is one of these at play until much latter. Similarly to the Cerebus Retcon, without Word of God, it can sometimes be hard to tell if the emergence of an overarching story was a later decision made because the creators wanted to try something new and/or realized their work had an underlying theme they can take advantage of, or if it was planned from the beginning and all the episodic content was meant to ease the audience into The Reveal. In the absence of confirmation, Arc Welding is YMMV.


Compare Canon Welding, which ties together different series, and Innocuously Important Episode, which retroactively ties a seemingly unrelated event into an existing Story Arc. See also Meta Origin, Patchwork Story, Plotline Crossover, Hyperlink Story. Under the right circumstances, Greater-Scope Villain and Greater-Scope Paragon 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.

Has nothing to do with welding metal using arcing electricity. For info on that, go here. For a minigame on that, go to Metroid Prime 3: Corruption.



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    Anime and Manga 
  • Bleach: Was the plot up to Big Bad 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 Big Bad 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. Word of God has indicated that the arc welding actually occurred at the end of the Soul Society arc when Tite Kubo realized 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 Retcons have been avoided, although several events (most particularly Masaki's death) have had to be Revisioned.
  • Naruto:
    • A minor example: A Filler episode of the original series revealed that Mizuki attempted to steal the kinjutsu scroll on 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 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 in the whole process.
  • Every subplot in Excel Saga, which were all Played for Laughs, actually got tied together in the surprisingly serious finale.
  • In Sailor Moon DiC tried to do this to all the bad guys that appeared during the second season. Then later Naoko Takeuchi did this with the bad guy Chaos at the end of the manga who was supposedly responsible for the appearance of all the previous Big Bads.
  • Tenjho Tenge. Every bad thing that ever happened to anyone turned out to be the work of the protagonist's dad. Even the stuff that happened centuries ago.
  • Yu-Gi-Oh! GX 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 Big Bad Darkness for...something.
  • Yu-Gi-Oh! 5D's, the villains of the first major story arc are Roman Godwin and 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 Ancient Conspiracy 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 Yu-Gi-Oh!: Bonds Beyond Time, was also an agent of Yliaster working on a secondary plan in that film.
  • Chapter 170 of Yu Yu Hakusho confirms that 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.
  • Pokémon Adventures tends to do this:
    • Both good guys and bad unexpectedly show up in later arcs with gambits ahoy, but FireRed and LeafGreen 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 "Holy Shit!" Quotient shot up to high levels.
  • Happened quite a lot in Fist of the North Star. A few volumes after Kenshiro's Token Motivational Nemesis 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.

    Comic Books 
  • Alan Moore 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 do something different, stating that he does this because readers would otherwise feel cheated that the stories they followed had no payoff.
    • In Swamp Thing, he famously resolved Alec Holland's quest to become human again by choosing to Take a Third Option, the Swamp Thing was never Alec Holland, the scientist was Dead All Along and his consciousness was absorbed by a swamp creature who believed he was "Alec Holland". This Downer Beginning resolved the Failure Is the Only Option nature of the premise, re-purposed and recycled supporting characters to give them new roles in a Darker and Edgier world, and Moore even allowed Alec Holland a Happy Ending reunion with his wife during Swamp Thing and Etrigan's journey to the afterlife.
    • In Miracleman, a Darker and Edgier reboot of the childish British originals, the bizarre and fantastical Mick Anglo 50s stories are retconned into artificial memories via Lotus-Eater Machine by the Big Bad, ensuring that the old stories had a context and importance to the modern version.
  • Buffy the Vampire Slayer:
    • The end of Season 8 sets up the the background of 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 Fray, if you notice the hovercars.
  • This often happens in Spider-Man. A most notable case is Gerry Conway's Parallel Lives, which while often seen as a Retcon or Revision, was actually an attempt to merge different parts of Mary Jane Waton's characterization over the Spider-Man continuity in a way that made sense, while reconciling gaps in her characterization:
    • Originally Lee/Romita introduced Mary Jane as an insensitive airhead who was constantly flirting and chasing after Peter in a way that was both a little insensitive and mean to Harry and Gwen, and which annoyed Peter to no end. Then Conway himself in his run building on Lee-Romita's characterization tried to develop her into a more compassionate, and courageous, person, as well as a loyal friend and companion who genuinely cares for Peter and loves him, and with whom Peter can be truly happy and relaxed in a way he couldn't with Gwen. After Conway left, Len Wein generally kept the couple as static while occasionally for the sake of drama having MJ be mean to Peter by flirting with Flash in Operation: Jealousy type gambits that left him confused, with many noting that MJ was "Gwen with sarcasm and sass" in this period, rarely building on Conway's work. Marv Wolfman, who followed Wein, had Peter propose to her and MJ reject it a little callously, seeking to end the relationship and shake the status-quo, but the second series (The Spectacular Spider-Man), still keeping in line with Conway's characterization, had her say she still loved Peter and was a little worried about taking the next step, and later Wolfman said that she did it because her parents divorced and wrote her out of the book.
    • When Roger Stern came and brought Mary Jane back, as a little older and more successful version of her teenage self, he also created a backstory that hinted at both her origins (with Aunt May saying that both she and Peter "have lost so much") and later an outline that as per Stern, Tom Defalco followed correctly, namely that she had known Peter was Spider-Man for a while and it was out of fear for his life and herself that she rejected his proposal and left New York. This explanation contradicted the one given by Wolfman where it was fear about her repeating her parents' divorce, and it didn't explain when she learned the secret and why she chose Peter's proposal to get out, since Spider-Man's adventures didn't impinge on her life in that period to justify her leaving.
    • Conway, feeling that Mary Jane's new backstory explained and deepened her early behavior and characterization, decided to have Mary Jane know from the very beginning since it both demonstrated clearly to readers how much her Lee-Romita facade was clearly an act, it heightened her courage to stay at Peter's side, made her earlier interactions and behavior with Harry and Gwen a little less mean, if still sarcastic and trollish, and provided a better motivation for her rejecting Peter's first proposal (he proposed without telling her his identity which she would obviously feel was indicative that he didn't trust her) and why she chose to reveal her Secret Secret-Keeper status to Peter and her own origins so shortly after she came back when the Puma attacked (since originally she said "I thought I could handle it before", which two issues later became a justification for her leaving New York).
  • Cerebus the Aardvark 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 Transmetropolitan starts its Myth Arc 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 Don Rosa's The Life and Times of Scrooge McDuck series, which takes every random reference Carl Barks 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.
  • Geoff Johns did this in the Green Lantern 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 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 in Green L Antern Rebirth. 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 Jack Kirby 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 Legion of Super-Heroes were also a Guardian offshoot.
    • Johns has established that the Guardians learned of the Emotional Spectrum from Volthoom, the First Lantern, and when he went mad with power, created the first seven Green Lantern rings to defeat him. Green Lanterns would reveal that the first seven Green Lanterns included a Kryptonian, a Coulan, a member of the Old Gods of the Third World, a White Martian, an ancient Tamarean, and an avatar of the Green. It also made the creator of the rings be Rami, a Guardian from the earlier Phantom Ring arc. And the Phantom Ring arc itself did it by making the main antagonist be Frank Lapinski, a minor character from Johns' Secret Origin arc.
  • In the Marvel Universe, the writers and editors of all of its comics revealed that Weapon X is in fact controlled by an organization that has existed since before WWII called Weapon Plus, a secret governmental organization hellbent on eradicating mutants, who is responsible (directly or indirectly) 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 the Uplifted Animal team Brute Force and a weird squirrel with Wolverine's powers (both Weapon II), The Skinless Man (Weapon III), Man-Thing (Weapon IV), Agent Venom (Weapon V), Power Man (Weapon VI), Nuke (One of Daredevil's villains and Weapon VII), Typhoid Mary (Weapon IX), 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 Word of God, 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 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, Word of God 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 its 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 their atrocious experiments and horrifying creations...
  • Wolverine: In volumes 3 and 4, and in Wolverine: Origins, Marvel decided to reveal Wolverine's 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 Starman managed to provide a coherent connection between the various characters who had used that name, even though with one or two exceptions, none of them had any relation, or indeed even the same powers.
  • In Ultimate Spider-Man, several Batman Cold Opens 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.
  • Kurt Busiek's Avengers Forever story indulges in arc welding throughout, revealing that 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 Archie Comics 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 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.
  • Sonic the Hedgehog (Archie Comics): During the "Enerjak Reborn" arc, Dr. Finitevus reveals how everything he's done since his introduction has been part of his grand plan to create a new 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 albino).
    • Issue 233: many of 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 make Ixis Naugus king of Acorn.
    • When the 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 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 Iron Man run, Frank Tieri created a rival for Tony named Tiberius Stone. Years later, Dan Slott brought Tiberius out of Comic Book Limbo and revealed that he was the ancestor of Tyler Stone, one of the major villains from Spider-Man 2099.
  • In Non Sequitur, Wiley frequently used three separate sets of recurring characters: everyman Joe and his drinking buddy, Bob, Bratty Half-Pint 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").
  • Like Moore, Grant Morrison is fond of doing this as well.
    • Grant Morrison's JLA:
      • The run does this to Johnny Thunder's thunderbolt and Aquaman character Quisp, revealing they both hail from the Fifth Dimension like Superman villain Mr. Mxzytplk. Appropriately, the Thunderbolt's summoning word "Cei-U" (pronounced "say you") was revealed to be his real name "Yz" backwards and Quisp's name was modified to "Qwsp".
      • The finale of the run, "World War 3", also doubled as a Fully Absorbed Finale to Aztek, revealing that the "Tezcatlipoca" Aztek was trained to deal with was, in fact, Mageddon, not the Wonder Woman villain.
      • The Phantom Zone, the Still Zone, and Limbo are all ultimately revealed to be different names for the same place.
    • Grant Morrison's Batman:
      • Pretty much everything in their run ties back to either Dr. Hurt and the Black Glove, or Talia's Leviathan organization.
      • It also sees Morrison tie a lot of stuff like Vandal Savage's origin and a lot of Batman's Silver Age adventures to Darkseid via the Hyper-Adaptor and its host Simon Hurt. In keeping with them doing this in their JLA run, Bat-Mite is also revealed to be a denizen of the Fifth Dimension and is the source of the Arc Words "Batman and Robin will never die."
  • Another Batman example: the climax of the Black Mirror arc reveals that 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 The Joker to cripple Barbara back in The Killing Joke, though it's unclear if that's true or if he's just screwing with her.
  • Jonathan Hickman's run of The Avengers reveals that Captain Universe, The New Universe 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.
  • When DC Comics rebooted the line with the New 52 in 2011, each September issue would be part of a themed month, such as the 2012 issues being "Zero issues" exploring the revised origins of DC's heroes. Rather than derail the series, The Flash instead tied the issues into the on-going narrative.
    • 2012: Zero issue - The debut of Daniel West, who would be revealed as the New 52's Reverse Flash over the course of the 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 Forever Evil mini-series.
    • 2014: Future's End - The issue ties directly into the Future Flash story arc that had been going on since April.
  • The Clone Saga 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 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 Nick Fury, the Incredible Hulk, and Sub-Mariner are just front organizations for a regrouped Hydra.
  • Onslaught does this with three elements:
    • When Bishop first appeared in the X-Men 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 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 Fatal Attractions could (and did) backfire (as it's what led into Onslaught).
    • A bit of characterization marching on was 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 Fatal Attractions, 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, DC Universe: Rebirth #1 revealed the true creator of the New 52 universe: Dr. Manhattan. The experiment at the end of the story gave birth to this world. Furthermore, the pre-Flashpoint and New 52 universes are the same universe.
  • In X-Men, 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 Jean Grey and the Summers brothers and ultimately resulted in the birth of Nathan Summers, a.k.a. Cable. Of course, this did give rise to the famous Continuity Snarl 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."
  • In Classic X-Men, a random story featuring Moses Magnum where he first got his superpowers was revealed to have been the result of the machinations of Apocalypse.
  • Supergirl: In Strangers At The Hearts Core, writer Jack C. Harris revealed that most of the criminals and Villains-Of-The-Month that bedeviled the titular heroine during his run were controlled by Lesla-Lar, Supergirl's first villain who had been defeated in The Girl With The X Ray Mind, published eighteen years earlier.
  • Al Ewing's run of The Ultimates (2015) 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. 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).
  • Ewing does it again in Avengers: No Surrender, having the previous times the Incredible Hulk came back from the dead, or had a close brush with death, actually be manifestations of his Resurrective Immortality, setting the stage for Immortal Hulk.
  • Incredible Hulk:
    • Immortal Hulk ties together the Leader's plots and schemes from over the last fifty years, turning most of them into part of his plan to figure out the secrets of Comic Book Death (except turning General Ross into Red Hulk. That was partly For the Evulz).
    • Meanwhile, a tie-in to Empyre for She-Hulk turns her near-death experience in the opening act of Civil War II into an actual death, as part of Immortal Hulk's exploration of Resurrective Immortality.
  • In its first arc, Geoff Johns' run on Teen Titans does this with two of the Titans' oldest enemies, Brother Blood and Trigon. Specifically, it's revealed that the former's cult is actually a Religion of Evil built around the worship of the latter.
  • The Detective Comics (Rebirth) story A Lonely Place for Living and the later Super Sons of Tomorrow crossover between Superman (Rebirth), Super Sons and Teen Titans (Rebirth) revealed the previously separate possible futures shown in Batman #666, the Titans of Tomorrow arc in Geoff Johns' run on Teen Titans, the Pax Batmana story in Batwoman (Rebirth), and O.M.A.C. are actually parts of the same future at different points in time, connecting several previously unrelated plotlines.
  • Similarly, Brian Michael Bendis' Legion of Super Heroes: Millennium welds many of DC's possible futures into a single timeline - President Supergirl, Batman Beyond, Kamandi, Tommy Tomorrow, Booster Gold, OMAC and finally a new incarnation of the Legion.
  • The 2018 Venom series connected the titular character's mythos to both Gorr the God Butcher and Knowhere by revealing that they're all connected to the villain Knull, the Symbiote God and creator of the Klyntar race. He decapitated a Celestial whose head become Knowhere. In said head, he forged All-Black the Necrosword (actually the first Klyntar, revealing the weakness to sound and fire that symbiotes possess are the result of inherited trauma associated with the fire of the forge and sound of the hammer hitting the anvil) and was the black-clad deity that Gorr stole the sword from.
  • Marvel Comics #1000 does a truly insane amount of welding in its bridging story. To whit: (deep breath) The backstories of the Golden Age Human Torch, short-lived Timely Comics characters The Ferret and the Xs, Captain America villain Adam II, Adam Warlock and his creators, the Black Knight, several different masked heroes with the name "Raider" from Marvel's Western stories, and Guardians of the Galaxy villain Michael Korvac are tied together into one narrative. Phew. And it's hinted there are some other connections to other characters not yet revealed.
  • When John Ostrander rebooted the Suicide Squad, the backstory tied Control (of the O.S.S.) and Jeb Stuart (of the The Haunted Tank) to the original Squad, as the civilian and military heads of Task Force X. Ace Morgan also makes an appearance as a flight school rival of Rick Flag, Jr.
  • Rat Queens is split into the original run and the Lighter and Softer retool. Once the retool had its legs under it, writer Kurtis J. Wiebe explained the original run as the alternate universe where the current villain originated. Further, the retool storyline was said villain probing the heroes for psychological weaknesses.
  • The Flash (Rebirth) #761 reveals that Reverse-Flash has been using Subliminal Seduction to keep the Flash Family apart, tying together not just Rebirth-Barry constantly pushing Iris away and failing to work with the other speedsters, but Wallace going along with Damian's Well-Intentioned Extremist actions in Teen Titans (Rebirth), Bart not telling his family he's alive in Young Justice (2019) and Wally covering up the accidental deaths he caused in Heroes in Crisis.

    Fan Works 

    Films — Live-Action 

  • Awake in the Night Land, which is set in the universe of William Hope Hodgson's The Night Land, linked this book to The House on the Borderland by stating that the titular house is the entrance to the House of Silence of The Night Land, but in the past.
  • The Dark Tower series is a major Arc Welding project for the works of Stephen King, bringing together multiple previously introduced concepts and characters for a Saving the World 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 'Salem's Lot and the "Low Men" from "Low Men in Yellow Coats" are both part of a massive army commanded by the mysterious Crimson King from Insomnia. Randall Flagg from The Stand and The Eyes of the Dragon is the Crimson King's Dragon, serving as his emissary on Earth.
    • The psychics Ted Brautigan (from "Low Men in Yellow Coats") and Dinky Earnshaw (from "Everything's Eventual") 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 The Shining and Carrie White from Carrie are similar such psychics, and that their abilities could also bring down the Tower if so utilized.
    • The mystical "Turtle" entity from 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 The Mist 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 The Stand, 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.
  • Doctor Who Expanded Universe:
    • The Doctor Who Missing Adventures novel Venusian Lullaby takes a lot of the 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 Past Doctor Adventures 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 Big Finish audio drama "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.
    • Original Sin establishes that Tobias Vaughn from "The Invasion" was responsible for various advanced technologies that plagued the Third Doctor, and also created the glitterguns from "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 ("Destiny", "Resurrection", "Revelation" and "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 Scrapbook Story) ties stories together to provide more of a narrative for each Doctor's adventures. Most blatantly, the Seventh Doctor section suggests that Fenric's manipulation wasn't just responsible for "Iceworld and Nemesis", but for almost everything that happened to that incarnation.
  • According to J. R. R. Tolkien, he didn't really hit on how to make The Hobbit and The Lord of the Rings fit together until he realized that the Necromancer (an entirely offscreen villain Gandalf was mentioned as going off to fight to get him out of the picture) could have been an alternate identity of Sauron. He also rereleased portions of The Hobbit to turn the One Ring from a nifty little magic item to an Artifact of Doom, justified as Bilbo now telling the true story after prompting from Gandalf.
  • All 7 other of the Incarnations of Immortality series, encompassing epic acts by Death, Time, Fate, War, Nature, God and the Devil had this trope. In the last novel in the series, Under a Velvet Cloak, 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 Known Space stories develop a bad case of this later on, as the hugely successful 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 2001: A Space Odyssey.
  • Lemony Snicket: The Unauthorized Autobiography played this for laughs. Most of the book consists of explaining how everything that had happened up to that point in the series was related to the VFD in various ludicrous ways.
  • The first Noob novel did this to some episodes of the original webseries, making it part of the Horizon storyline. When an episode of Season 1 needed to show a character doing Fetch Quest (which happened three or four times out of twenty often stand-alone episodes) the Quest Giver always happened to be In the Hood and dressed in Black Cloak, something that could easily be normal for the game and/or due to No Budget. The first novel, chronologically set after the first season, reveals that the black cloak is actually a trademark for a group that is after the Dismantled MacGuffin 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.
  • Sherlock Holmes: It was revealed, in the first of the two stories by Arthur Conan Doyle 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 Star Trek Novel Verse books:
    • The Star Trek: The Next Generation novel Q & A has every Q-episode of TNG as being part of a long term plan to 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.
    • Similarly, the Star Trek: The Next Generation 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 Star Trek: The Original Series too.
    • Peter David is quite fond of this. In Vendetta, the planet-killer from The Doomsday Machine turns out to have been engineered by a long-dead race as their final revenge against the Borg.
    • Star Trek: Forged in Fire ties Sulu's captaincy of the Excelsior (as seen in The Undiscovered Country and explored further in Star Trek: The Lost Era) to the Blood Oath plot from the eponymous episode of Star Trek: Deep Space Nine. 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 Star Trek: Enterprise and Star Trek: Vanguard.
    • The Star Trek: Typhon Pact novel Paths of Disharmony links the Star Trek: Vanguard story arc to those of the Star Trek: Deep Space Nine Relaunch and the post-Star Trek: Destiny line, making it all relevant to the current events of the novel.
    • A rather pleasing example in the Star Trek: Voyager Relaunch with the exploits of Kahless, retroactively linking the novel line's Klingon saga to the relaunch in interesting ways. In Star Trek: A Time to..., 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 Hurricane of Aphorisms when the ruse was discovered. In the Star Trek: Voyager Relaunch, though, it's revealed why he was on Cygnet IV specifically. 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 Continuity Lockout, 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 Plot Hole 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 Star Wars Legends sources tie in many of Palpatine's and especially Thrawn's actions as being to prepare the galaxy for 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 Face–Heel Turn in Legacy of the Force is seemingly being tied to the Big Bad Abeloth in Fate of the Jedi.
    • Another example is Cade Skywalker's unique abilities in Star Wars: Legacy. His ability to sense vulnerable fractures has been tied to Mace Windu's sense for more metaphorical "shatterpoints" from 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 Revenge of the Sith. And considering that other sources hint that Plagueis created Anakin, it may be connected to that too... though that was Jossed in the Darth Plagueis 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 Star Wars: The Clone Wars.
  • Some Warrior Cats 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.

    Live-Action TV 
  • Graem Bauer and the "Bluetooth Group" in 24. 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 The Man Behind the Man, 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 Big Bad, Alan Wilson, to have been behind even the Bauers' involvement, and the ultimate authority over the Season 5 conspiracy, being head of a powerful group that had been manipulating events for some time and remained at large at the end of the season. Then the storyline disappeared without a trace.
      • The arc technically got resolved with a Hand Wave in Season 8. It is mentioned that Alan Wilson’s entire group got discovered and arrested offscreen after the end of Season 7. Quite the anticlimactic end to such a supposedly powerful group.
  • Agents of S.H.I.E.L.D.:
    • Various, seemingly independent threats throughout Season 1, such as Project Centipede and Ian Quinn's corporation, are eventually be revealed to all be orchestrated by the same Big Bad, the Clairvoyant who turns out to be a HYDRA agent, tying into the events of Captain America: The Winter Soldier.
    • One of Season 2's initial main villains, "the Doctor" (Calvin Johnson, aka Cal Zabo, aka the comics Mr. Hyde) is revealed in the second half of the season to have been working on (as he perceived it) the behalf of his wife, Jiaying, who eventually serves as the season's Final Boss. She, in turn, can blame her Start of Darkness on 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 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 Big Bad Elena Derevko's master plan.
  • One of the more explicitly identified examples of Arc Welding comes from 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 Gambit Roulette. (It's known that this was all one big retcon because it wouldn't have worked without Charisma Carpenter's real-life pregnancy.)
    • A smaller version then happened in the next and final season: faced with Executive Meddling to be more episodic without any arcs, after finding out the show would be canceled anyway, Joss Whedon 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.
  • 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 Brother Blood and Slade, in order to give 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 Malcolm Merlyn was responsible for the shipwreck that stranded Oliver on the island to begin with.
      • Season 2's storylines are connected by Mirakuru. It was his search for it that led Dr. Ivo to the island in the flashbacks, it's being used as part of Brother Blood's plans in the present, and it's responsible for Slade's Face–Heel Turn in the flashbacks that leads to him being Big Bad 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 The Dragon to Ra's Al Ghul in the present. The final episodes tie the storylines more tightly together, however, as 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 Villain of the Week in one episode's present setting and served as part of Andy Diggle's Start of Darkness. Also, the magic idol that flashback villain Baron Reiter is after also serves as 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 Big Bad 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.
  • Battlestar Galactica (2003) 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.
  • The Blacklist:
    • From the start, it was clear that 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 the Cabal enough that he can 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.
    • The Season 5 finale, "Sutton Ross", pieces togethers hints and clues scattered throughout the entire series up to that point for The Reveal that the man calling himself Raymond Reddington is in fact a fake pulling a Dead Person Impersonation.
    • Despite airing years after the Cabal Story Arc ended, the Season 6 episode "Minister D" wraps up a few dangling threads from it, and shows how they tie together into the larger Myth Arc. Specifically, it's confirmed that Katarina Rostova was an agent of the Cabal in addition to her work for the KGB, and that when Reddington came into possession of the Fulcrum, she helped the Cabal frame him for the treason that sent him on the run and hired the Red we know to steal his identity after his death in order to further ruin his name.
    • "Bastien Moreau: Conclusion" spells out exactly how the chain of Blacklisters from the first half of Season 6 are all linked together in Red's plan to expose a Government Conspiracy in exchange for clemency from his looming death sentence.
  • In season two, Charmed (1998) established that the girls' mother, Patty, had had a Forbidden Romance with her Whitelighter, Sam. At the time, this was mostly to create a parallel to Piper and Leo's relationship. However, when a fourth sister needed to be introduced two seasons later, making her half-Whitelighter provided a handy explanation for why she needed to be hidden away until now.
  • 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.
  • The Defenders (2017) bridges together the two different plot lines involving the Hand introduced in previous series. In Daredevil, they're established as being in a Secret War with the Chaste, while in Iron Fist (2017), they're stated to be ancient enemies of 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.
  • Doctor Who:
    • There was a bit of Arc Welding near the end of its original run, when Ace's involvement with the Doctor between "Dragonfire" and "The Curse of Fenric" (eight multi-part stories over three seasons by that point) was revealed to be part of Fenric's Batman Gambit to trap the Doctor (moral of the story: don't try a Batman Gambit against a Chessmaster). It also provided a bit of disappointment for Classic Who fans when the series returned and "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 "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 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 Cyberking stomping around Victorian London is retconned to have been another casualty of the cracks in time.
    • "The Time of the Doctor", the Eleventh Doctor's Grand Finale, 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 Myth Arc.
    • In Clara's first appearance in Series 7, "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, "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, "Death in Heaven", where it's revealed that that woman was Missy, who brought Clara and the Doctor together as part of her larger overall scheme against the Doctor.
  • A similar event occurred in Firefly, another Joss Whedon show. Although the Reavers and River's torture at the hands of the Alliance are introduced in the pilot episode, the 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 28 Days Later, and the reason that River is being so strongly hunted by the Alliance is that she knows secrets like this.
  • Kaizoku Sentai Gokaiger episode 40, which not only turns the Gokaigers' Early-Bird Cameo (a Big-Lipped Alligator Moment during the Goseiger/Shinkenger Reunion Show) a canon event, but also ties into the team's quest of Gotta Catch Them All.
  • In the old Kamen Rider 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 Gorō Naya. 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 Tomokazu Seki, though he doesn't take credit for seasons he wasn't in. However, the Non-Serial Movie of Faiz gave the Big Bad three Man Behind the Man 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 Big Bad instead of just behind the Big Bad... 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 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 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 Timelines.
  • Power Rangers had two major examples of this:
  • At the end of the first season of The Sopranos, Big Pussy has vanished. 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 The Mole, with him being a second one.
  • Star Trek:
    • Deep Space Nine does excellent examples of Story Arcs 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 Myth Arc of the show.
      • Also, Executive Meddling resulted in the Klingons returning to their Kirk-era level of villainy just as the Dominion was planned to take center stage. The Powers That Be did the best they could, and made it fit at the end by making Changeling manipulation responsible.
    • Star Trek: Discovery's second season finale "Such Sweet Sorrow" does this the entire franchise. How come, despite it being this super awesome ship with a unique warp system, the Discovery was never mentioned by Starfleet or any of its plethora of members? How come Spock never mentioned he had a sister the entire time? Simple - Starfleet sealed everything about the ship, its crew and its system to protect the fact that it had been shot into the future with some of its crew to make sure the AI that tore through Section 31 couldn't come back.
  • Stella used one frequent actor to set up an arc for the series.
  • Supergirl (2015): The episode "The House of L" ties together two of Season 4's major storylines, as Lex Luthor is revealed to have helped Ben Lockwood set up the Children of Liberty as patsies for his larger plan, and has also been helping Kaznia train the Supergirl clone known as Red Daughter.
  • Arc Patching, if not Arc Welding, was done in Veronica Mars, 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 The Reveal 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.
  • 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.
  • The X-Files 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: Between the Buried and Me do this with their Parallax storyline when it's revealed that Prospect 2 was 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".
  • Marilyn Manson'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 are space 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.

    Tabletop Games 
  • Up until the Invasion block of Magic: The Gathering, the storylines of the sets before were mostly World Building 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 Big Bad 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 D&D setting Ravenloft retroactively Arc Welded its first six adventures together into the Grand Conjunction story arc, using a Vistani prophecy as solder.
  • Arguably, the D&D settings Planescape and Spelljammer, both of which were specifically created to allow the numerous other settings of D&D to mix with each other.

    Video Games 
  • Metal Gear:
  • In Guild Wars 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 Big Bad of Factions.
  • The Chzo Mythos 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.
  • Mega Man:
    • "Evolution requires sacrifice." Spoken by Lumine of Mega Man X8 and Serpent of Mega Man ZX, this refers to the evolution of the 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 Video Game Remake (and possibly Continuity Reboot) Mega Man: Maverick Hunter X, Sigma begins spreading these beliefs himself. If the reboot series wasn't axed, the developers could have elaborated on the concept even more.
    • Meanwhile, in Mega Man Zero, unlike the two series that preceded it, there is a different Big Bad for the first two games (Copy X and Elpizo, who are trying to wipe out Reploidkind and humans, respectively). Then, that novelty just had to be shot down by Zero 3, wherein that game's Big Bad, Dr. Weil, can be easily marked responsible for the events of the previous two note , legibly making him the Greater-Scope Villain for the entire Zero series.
    • Wily claims to have orchestrated Mega Man Battle Network 2 at the end of Battle Network 3, making the first three games in the series one saga about Wily's plots to destroy the Internet (really) culminating with the Alpha plan in 3.
  • King's Quest: Dahlia, Hagatha, Mannanan, and Lolotte all appeared to be generic evil wizards and wicked witches. But then, we hear that the Big Bad in King's Quest V is the "brother" of Hagatha and Mannanan and looking for revenge. Then King's Quest VI has a single, damning letter alluding to the "Brotherhood of the Black 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. Oh, Crap! Fanon, especially the Fan Sequel and Fan Remake games will cheerfully run with this theory.
  • For almost 20 years, Sonic CD was a Gaiden Game 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 Sonic 2, most fans just assumed it was a prequel.) However, as of the new remake for Xbox Live, PlayStation Network, and iPhones, features were added suggesting (and Word of God asserted) that it actually occurred sometime before Sonic 4, and it's specifically tied to Episode II.
  • The four Downloadable Content packs of Fallout: New Vegas are part of a bigger storyline which lead to the confrontation of the player-character, The Courier with Ulysses, The Rival.
  • Super Robot Wars is a Massive Multiplayer Crossover series of Humongous Mecha shows. Many games often do this by drawing on similarities between different series to weave common bonds.
    • The biggest example occurred in the first Super Robot Wars Alpha game. The Big Bad has an extremely long sequence where he explains how he was behind everything in every series that was in crossed over in the game. This created a meme in the Japanese fanbase where the villain claims responsibility for just about everything. Then in the second Super Robot Wars Original Generation game, the Big Bad of Alpha reappeared and made another long speech about how he was behind everything. It's fully Ascended Meme.
    • Super Robot Wars UX:
      • By the way, 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 "Machina" and the 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.
      • Tatsumiya Island is a part of the 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 and gets her KYUNKYUN beam, then during SKL finale she goes super mode when Kiba shows up, and during Fafner TV finale, she gets her Morale boosting special command. 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 basically from a previous incarnation of the world. 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.
    • Super Robot Wars V:
      • 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 Space Battleship Yamato 2199 and 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 Char's Counterattack.
      • Draconium is derived from the 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.
      • Aeolia is also another member of the Ancient People who seeks to overthrow Embryo.
      • Ruri is another successful Ultimate Coordinator.
      • 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 Getter Robo Armageddon is folded into the plot of Shin Mazinger, such as Great Mazinger and Mazin Emperor G being powered by both getter rays and photonic energy and Kenzo Kabuto constructing the Shin Getter Dragon.
      • Banjo Haran was raised on Mars, meaning he's an A-Class Jumper and thus capable of Boson Jumping.
    • Super Robot Wars X
  • Pokémon Mystery Dungeon: Explorers had few story arcs in the first place, but near the end of the game, you find out that Darkrai was responsible for both Primal Dialga and Palkia trying to remove you from time and space respectively.
  • Star Trek Online 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 Star Trek: The Motion Picture.
    • Near the end of Star Trek: Deep Space Nine, a group of Dominion ships is threatening to invade the titular DS9 by way of the Bajorian wormhole when suddenly they just disappear! They return in the Featured Episode series "The 2800".
    • Probably the biggest one? The game's true Big Bad? 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 Star Trek: The Next Generation and Star Trek: Deep Space Nine. Even worse, it's them who had helped caused the destruction of Romulus and Remus in the backstory to Star Trek (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 "Divide ut Regnes", which in the process of fixing the much-maligned "Divide et Impera" finds time to retroactively explain two aspects of the mission "Preemptive Strike": why the Romulans are preparing to attack the Federation, and how Admiral T'nae knew about it.
  • The first four games in The Elder Scrolls series consist of largely unconnected stories set in the same world. However, the fifth game of the main series, Skyrim, does some Arc Welding which connects the overall stories in its main quest. Specifically, the destruction or removal of a various Cosmic Keystones and metaphysical "Towers" in the previous games herald the return of Alduin, the Big Bad Beast of the Apocalypse who was cast out of the stream of time in the past but prophesied to return.
  • The Artix Entertainment writers are so guilty of this trope it's not even funny. The most obvious example is their first and flagship game, 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 Kirby games, while sometimes direct sequels to one another, are usually episodic. Around Kirby's Return to Dream Land, 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 Kirby Super Star's NOVA), the Dimension Mirror from Kirby & the Amazing Mirror being the cause of Queen Sectonia's tyrannical personality in Kirby: Triple Deluxe, Kirby: Planet Robobot's Final Boss bearing a strong resemblance to NOVA, even having wish-granting powers and a similar Heart Drive that's fought as a boss, and Kirby Star Allies making implied connections between the game's antagonists and Dark Matter from the so-called "Dark Matter Trilogy", due to Hyness' Motive Rant and Void Termina's final form.
  • When it was originally released, the whole Metroid Prime Trilogy (despite the Prime name becoming the primary moniker for mainline 3D Metroid games) was designed to be a series of Gaiden Games story-wise, not having any major effect on the series' primary Myth Arc involving the war against the Space Pirates, mostly just showing the status quo being maintained during the Phazon Crisis. The games did not have the "direct" involvement of series co-creator Yoshio Sakamoto, but interviews have noted he had to approve the storylines of the Prime games in order to make sure they didn't contradict the main storyline and is quoted as saying making them completely non-canon would have been "a cop-out." Indeed, Japanese manual for Zero Mission did show the placement of the early Prime games in a timeline on the table of contents. Despite this, the Prime games could be completely ignored in the grand scheme of the series and didn’t have any major ties to the main lore, serving as something more akin to an expanded universe for a long time. Even Other M, which had Sakamoto's more direct involvement, mostly ignored and glossed over the events of the Prime series outside of some very light acknowledgement in the form of the Seeker Missiles and some more substantial, but lost in localization acknowledgement via Project "Metroid Warriors", which shares the same Japanese name as a Pirate Log from Prime 1 involving the space pirates attempting to eliminate the Metroids' weakness to cold and alludes very briefly to the Pirates' own efforts, in spite of Sakamoto's insistence in interviews that they "took cues" from the Prime games. This caused some minor Continuity Snarl with Ridley, as he went from being a near completely cybernetic being to being completely organic again at the start of Super Metroid without any apparent explanation, even if we accept Word of God at the time of the Prime trilogy's release that Ridley survived both the first Prime and Corruption intact without being too much worse for wear in either case. It wasn't until Samus Returns, a remake of Return of Samus, when the Prime series was finally connected in a substantial manner with the "primary" arc, where newly added Final Boss Ridley appears with his cybernetic body parts after his time in the Prime trilogy, showing he's almost completely healed at the time of Samus Returns, and a post credits scene showing him having completely discarded the armor and chasing Samus to the Ceres Space Colony, now fully organic and closing the plot hole. The fight even foreshadows Ridley’s confrontations in both Super and Other M while it's at it, effectively bringing the entire series thus far together into a singular cohesive narrative. Not to bring up all the other aspects of the greater Prime trilofy lore that was brought back up in the game, at least the lore that involved the Chozo.

    Visual Novels 
  • Ace Attorney Investigations: Miles Edgeworth:
    • In both games, the first four seemingly unrelated cases turn out to have all been part of the Big Bad's Batman Gambit. 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, 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 Big Bad. Considering most of the references to non-Investigations games being little more than The Cameo, this one stands out. Meanwhile, 2 also ties in the main arc of the first game to an even greater scale, due to the Inherited Turnabout prominently featuring playable segments as the Gregory Edgeworth during his ultimately-fatal last case. Due to tying it in with the Investigations games' Myth Arc, the events behind his final case against Manfred von Karma are given even more significance in the grand scheme of things.
  • Despite Nine Hours, Nine Persons, Nine Doors feeling like a self-contained story, its sequel Virtue's Last Reward 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 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.
  • In Fallen London, the player themselves can engage in a tiny bit of this at one point in the "Seeking Mr. Eaten's Name" Story, where the player character is asked why they persist in their quest despite their assured destruction. You can choose from over a dozen (!) possible responses, and some of them reference Stories that occurred earlier in the game. For example, you can imply that your character has never been the same since, say, their visit to the Iron Republic or being exiled from the Shuttered Palace.

    Web Comics 
  • It's Walky!/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).
  • Dominic Deegan: It turns out 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.

    Web Original 
  • SCP-2000 double-checks the welding around the SCP Foundation. 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".

    Western Animation 
  • Various jokes and gags made in the purely episodic first season of Adventure Time either return in later seasons to add to the show's overall Myth Arc, 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 takes an early throwaway gag of Marceline constantly moving all over the Land of Ooo, and explains that the main reason for this is to avoid 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 Clone High's final episode, where the 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 literally every character ever to appear on the show — except Scudworth — frozen inside a meat locker.
  • The 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.
  • 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 Story Arc 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 Story Arc finale.
    • Also, many unrelated aspects of the first half of the series were ultimately revealed as part of the Archmage's far-reaching Batman Gambit for world domination.
  • Used not in Gravity Falls, 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.
    • Word of God confirms that the first season's Monster of the Week 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 Story Arc in season 2.
  • Interviews with the creative team behind Justice League Unlimited 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. Cadmus turns out to have been responsible for two previously encountered (groups of) villain, Doomsday and the (Joker's) Royal Flush Gang. The ultimate reveal of the Big Bad, Brainiac, actually connected back to an episode of Superman: The Animated Series, 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 Batman: The Animated Series that was the very first entry in the DCAU, and even some Call Forwards to the chronologically-last, Batman Beyond.
  • The Legend of Korra: "The Stakeout" reveals that Unalaq, the Big Bad 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.
  • My Little Pony: Friendship Is Magic:
    • Throughout Season 4, each of the Mane Six gets a focus episode during which they receive a gift, which at the end is shown giving off a rainbow glow. In the season finale, these are revealed to have become the keys to open the mysterious box which emerged from the Tree of Harmony in the season premiere.
    • Several episodes throughout Season 7 feature stories about various legendary heroes from Equestria's past. The season finale reveals that all of them, along with Starswirl the Bearded (another legendary figure, mentioned repeatedly since Season 2), were part of the same group, the Pillars of Harmony.
  • Season 3 of OK K.O.! Let's Be Heroes does this for some plot elements from the previous two seasons:
    • Foxtail, the Anti-Villain Big Bad of Season 2's P.O.I.N.T. arc, is revealed to have gotten the glorbs she used to illegally power up P.O.I.N.T. Prep students from Shadowy Figure, K.O.'s Arch-Enemy and the series's final Big Bad, who's shown an interest in almost every one of his appearances in obtaining these glorbs to sell on the black market.
    • Three characters who had previously never so much as appeared in the same episode together turn out to have a very important connection : 1) Laserblast, a Posthumous Character who's important to the P.O.I.N.T. backstory and storyline because, among other things, his death was the aforementioned Foxtail's Cynicism Catalyst that led to her becoming a Well-Intentioned Extremist. Oh, also he's alive and K.O.'s father; 2) Professor Venomous, Boxman's business partner who has begun to take a more active role in attacking the Plaza and antagonizing the heroes, and 3) Shadowy Figure, the aforementioned Arch-Enemy of K.O. who tries to steal glorbs and get K.O. to give in to his anger and unleash his Superpowered Evil Side. This connection is that all three of them are the same person. Laserblast made a Face–Heel Turn and became a villain, adopting "Professor Venomous" as his new alias; Shadowy Figure, meanwhile, is his Split Personality Turbo form.
  • The South Park 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 Stroker and Hoop 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. Its eventually revealed to be a no name background character whose appearance changed in each encounter with the duo save for his voice.
  • Transformers Animated 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, also the Autobots' ship, as an old friend. The third season reveals that 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.


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