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Fanon Welding

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Bart: Well you know what I think? I think Casper's the ghost of Richie Rich.
Lisa: Hey, they do look alike!
Bart: I wonder how Richie died...
Lisa: Perhaps he realized how hollow the pursuit of money is and took his own life.

In the world of Epileptic Trees, Fanon Welding is what happens when fans see Shared Universes and Stealth Sequels where there are none; a specific breed of fan theory which argues that a particular work somehow secretly shares a universe and/or continuity with another unrelated work, no matter how bizarre the possibility is and regardless of their respective authors' intentions. To support these theories, fans will seek out any supposed link between the works in question as proof that the events and elements appearing in one work were canonical to the other all along.

In other words, it can be considered the act of engaging in unofficial Canon Welding.

This commonly happens with works that happen to come from the same author, as they often tend to share similarities in style; it is especially guaranteed if they also contain Company Cross References to one another or share some specific Recurring Element despite taking place in entirely different continuities. Another common source of Fanon Welding theories is typecasting, the practice of having an actor play the same character type in works they appear in. As such, expect fan theories about similar characters played by the same actor in multiple works all being one and the same, or somehow related, thus making said works connected to each other. (Though Playing Against Type won't stop fans from believing any character played by the same actor is one person, regardless.) Other reasons may vary: maybe there is an expy of a particular character, or a character with a Reused Character Design, but the fans think the former is actually that very same character under a different identity, and believe the latter is a pre-established one all along. Or maybe the respective authors of two works happen to be friends, and both are fond of including Easter Eggs as references to each other's work.

When such theories come to be accepted by the fandom and incorporated into Fanon, expect to see many crossover fics involving the works claimed to be canonical to each other. If Word of God confirms the works in question to be indeed related all along, then it's Canon Welding.

Compare Common Crossover, where the works in question are featured notably often in crossover fics, but aren't necessarily considered to be unofficially canonical to one another. Also compare with the Doppelgänger Crossover, a trope where multiple characters sharing common features, voices, and/or actors are either brought together or revealed to be the same universe somehow.


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    Anime and Manga 
  • Giant Robo: The Day the Earth Stood Still features the Eiffel Tower being melted and bent over by the Vogler Sphere at the beginning of the series, which is how it appears in both Fist of the North Star and Mobile Fighter G Gundam, fueling speculation that they all take place in the same timeline. It helps that they all feature similar depictions of martial arts, and that Yasuhiro Imagawa directed both Giant Robo and G Gundam, as well as a spin-off OVA for North Star.

    Comic Strips 
  • Frazz is speculated to take place in the same universe as Calvin and Hobbes, with many theorizing that Frazz is an adult Calvin due to their similar designs and hair style. It helps that both share a very similar art style.

    Film — Animated 
  • Disney Animated Canon:
    • Some people think that Frozen and Tangled take place in the same universe, as two background characters in Frozen were deliberately modelled after Eugene and Rapunzel from the latter movie. This also led fans to believe Rapunzel is also part of the same family as the royal sisters, usually as their cousin.
    • There is another theory that Frozen and Tarzan take place in the same universe, and that Tarzan is the royal sisters' brother, who was born after the parents' boat crashed. This is debunked because we actually get to see Tarzan's parents who look nothing like the sisters', and Frozen II confirms that the ship didn't wreck in Africa.
    • Owing to their similar art-styles and Friendly Fandoms, many Zootopia fans believe Robin Hood to be the same world's distant past, often with Nick Wilde being distantly related to Robin.
    • There are some fans who believe that every movie in the animated canon takes place in the same universe, not only due to the above two theories, but also due to many of the movies sharing similar elements, such as talking animal sidekicks and magic.
  • The Pixar Theory, a fan theory (or group of theories) that postulate that all Pixar movies are part of a shared universe, using the different Easter Eggs as proof of that. Of course, the details of such connection will depend on who you ask,as the theory already has several notable exponents like the credited creator of the theory himself, Jon Negroni, the Super Carlin Brothers, and countless fan theories on Reddit and other forums from many others. In case you're wondering, Pixar creators have already debunked it to varying degrees. Pete Doctor (Monsters, Inc., Up, Inside Out) dismissed it, but admitted that all his films could potentially work within a single universe. Meanwhile, Brad Bird (The Incredibles, Ratatouille) is explicit about all his films (not counting sequels) taking place in different universes, much less all of them being within a larger Pixar-verse. Additionally, Word of God regarding the Toy Box world in Kingdom Hearts III indicates that the universe of the Toy Story films is canonically one of the worlds in the multiverse of Kingdom Hearts (as opposed to a Broad Strokes alternate retelling like most Disney worlds in the series). One could reasonably interpolate that if the same is true regarding the Monstropolis world, then at least those Pixar movies operate on the Kingdom Hearts Multiverse Theory. This was eventually discussed and debunked by the producers of Toy Story 4.

    Film — Live-Action 
  • Some fans of DodgeBall: A True Underdog Story and Heavyweights believe that White Goodman and Tony Perkis are the same character, mainly because both characters are cruel, egotistical fitness gurus played by Ben Stiller.
  • Nicolas Winding Refn's movies Drive (2011) and Only God Forgives are often thought to be connected (usually with the latter being a prequel to the former), because both movies star Ryan Gosling playing similar characters.
  • Due to Event Horizon's story fitting, both plotwise and atmosphere, the tone of Warhammer 40,000, many fans considered the film as a prequel when humanity makes its first contact with the Warp and its dark powers.
  • Fight Club: A bizarre but popular theory posits that the movie is secretly a Darker and Edgier sequel to Calvin and Hobbes of all things. Jack — the movie's protagonist — is theorized to be the disillusioned adult version of Calvin, and that Hobbes — Calvin's ambiguously imaginary friend — lives on in the form of Tyler Durden, Jack's villainous alter ego. Marla and Bob from the movie are also speculated to be the adult selves of Susie and Moe respectively, the latter presumably having developed his signature man-boobs as Laser-Guided Karma for bullying Calvin in the past.
  • Get Out (2017): Fans theorized that the film takes place in the same world as Being John Malkovich due to both movies featuring people forcibly taking over other people's bodies as a plot point and Catherine Keener as an actress, also theorizing that Keener's characters are one and the same. The directors of both films liked the theory.
  • A lot of Indiana Jones fans consider Gunga Din a direct prequel to Indiana Jones and the Temple of Doom due to the similarities between the two films, and the fact that the Thugee are the villains in both films.
  • There is a fan theory that suggests Life (2017) is a Stealth Prequel to Venom (2018), speculating that Calvin — the alien life form that the crew come across — is actually a Symbiote from the Marvel Universe because of its similar design and ability to absorb its prey. This was partially fueled by the fact that the former movie recycles a minor shot from Spider-Man 3, which was Venom's debut in live-action.
  • The Rock: One of the main characters of the film is John Mason, an aging British MI-6 agent played by Sean Connery. Mason was meant to be an Expy and a deconstruction of James Bond — sharing many traits such as being a Cultured Badass, The Casanova and a bonafide Escape Artist — along with being a deliberate Actor Allusion towards Sean Connery's fame as the first actor to play the James Bond character in film history. However, this also spawned a popular theory that claims John Mason is not a separate character, but James Bond himself, and "John Mason" is simply an alias he is using during the events of the plot.
  • Much of the fanbase of Showgirls believe that Nomi Malone is actually a grown up Jessie Spano from Saved by the Bell who never got over her addiction to caffeine pills and continues to have nervous breakdowns.
  • A popular theory, first proposed by YouTuber Rhino Stew, suggests that Snowpiercer is a Darker and Edgier sequel to Roald Dahl's Charlie and the Chocolate Factory. To sum up, he pegs the main villain Wilford as a grown-up Charlie Bucket who took Willy Wonka's (or rather, Wilford Wonka's) name after he inherited the factory, with the many similarities and shout-outs found in the details of both stories' characters and plots indicating that he was influenced by Wonka's philosophy, put some of the technology that powered Wonka's factory into the titular train, and used Wonka's psychological and organizational methods to establish his rule over the train's passengers. He also pegs a number of Wilford's henchmen as the other Golden Ticket winners (or their children) all grown up, and the train's dependence on child labor as a result of the Oompa Loompas going extinct. This video by Nomadic Kong builds on the "Wonkapiercer" theory, arguing that the plot of Snowpiercer draws direct parallels and homages to Charlie's 1971 film adaptation, Willy Wonka & the Chocolate Factory, right down to specific scenes that are nearly identical and even the use of "Pure Imagination" in the score.
    Rhino Stew: They're both two movies about groups of people that work their way through a large, fantastic structure. One by one, a person from the group is removed in each room, until one person makes it to the very end, who then found out that the entire thing was a test because a wealthy industrialist needed to find a new successor.

  • The Salmon of Doubt, the fragmentary third Dirk Gently novel, has an unnamed ginger-haired actor in a minor role. Since The Hitchhiker's Guide to the Galaxy describes Ford Prefect's hair as "wiry and gingerish", his cover story on Earth was an out-of-work actor, and Douglas Adams was talking vaguely about rewriting the whole thing as the sixth Hitchhiker's book before he died, it's a popular assumption that this is him.
  • A popular theory — proposed by science fiction writer John D. Clark in 1956 (making this trope Older Than Cable TV) and promoted by various other professional writers and scholars such as William Stuart Baring-Gould — suggested that Nero Wolfe is the son of Sherlock Holmes, generally the product of an affair with Irene Adler. Although others have argued in favor of Mycroft Holmes as a likelier candidate for Wolfe's father, citing the physical and psychological similarities to the elder Holmes brother. As discussed on this Wikipedia page, the novelist John Lescroat created a character called Auguste Lupa, who is implied to be Wolfe himself pulling a This Is My Name on Foreign, and who is explicitly Holmes son.
  • "Blackbury" was Sir Terry Pratchett's go-to name for Everytown, UK, but it's certainly not impossible that the Nomes Trilogy and the Johnny Maxwell Trilogy take place in the same Blackbury, especially as they both feature the Neil Armstrong Shopping Centre. Adding every mention of Blackbury in the Buck's Free Press children's page is doable, but a bit more of a stretch, since you end up with a Blackbury in which so much weird stuff has happened that Johnny's status as the town Weirdness Magnet is under threat.
  • Wildbow leaves references to his other works in each of his stories, usually in the form of one world having a warped retelling of the other world's story in a different medium. Since Worm and sequel Ward have a canonical multiverse, it's theorized that Twig and Pact note  also take place there on worlds that haven't been accessed via portal yet, and the stories are a result of alternate dimension shenanigans.

    Live-Action TV 
  • If a character from an entirely unrelated work just happens to possess certain traits such as a colorful, eccentric fashion sense, means of time travel, knowledge of past and future events, high intelligence and problem-solving, bizarre, reality-defying technology, British mannerisms, the ability to regenerate into an entirely new person/being played by several different actors, etc., you can be sure that people will start crafting crazy theories about that character secretly being a Time Lord/Lady of Doctor Who fame, whether jokingly or unironically. On This Very Wiki, it is an unavoidable meme to make these assumptions on Wild Mass Guessing sections to the point that we have an entire WMG page dedicated to them.
  • The Big Bang Theory and Two and a Half Men have been thought to take place in the same universe, because in one episode of The Big Bang Theory the cast are watching Show Within a Show Oshikuru, an anime series that Charlie in Two and a Half Men wrote a theme song for (and the same jingle is heard in the Big Bang episode). Both shows being produced by Chuck Lorre probably has something to do with it.
  • There is a longstanding (not entirely serious) theory among Blake's 7 fans that The Federation in Blake's 7 and the Federation in Star Trek are one and the same. Since it is canonical in the former show that the Federation controls the media and deliberately distorts what is fed to the public to suit its agenda, e.g. Roj Blake's show trial, the theory claims that the adventures seen on Star Trek are also propaganda created by the Federation to keep the population sated. Supporting this theory is that the Federation symbol in Blake's 7 is essentially the Star Fleet symbol turned on its side.
  • There's a rather popular fan theory that Booth in Bones is the reward or shanshu of Angel. They like to point out how similar Booth and Angel are and it's well-known that the Buffyverse has countless different dimensions. Since the shanshu was translated as become human and live until he dies, these fans like to think Angel was given Booth's life as his reward, only with no memory of his previous life. A few former Buffy alums having appeared in Bones just adds to it.
  • Brooklyn Nine-Nine is often thought to be in the same universe as The Good Place, with Michael Schur's other shows sometimes being brought in as well. They share a ton of cast and crewmembers, as well as sharing similar values and senses of humor. The most common theory linking the two is the idea that Eleanor Shellstrop might be Jake Peralta's half-sister; he's confirmed to have at least three siblings he knew nothing about until he was an adult, and the two characters have very similar personality traits and quirks.
  • Buffy the Vampire Slayer and Firefly get it a lot because both are Joss Whedon shows. It helps that Whedon intended to have Spike make a cameo in a bar if the series had continued.
  • Some fans of CSI: NY and Forrest Gump posit that Det. Mac Taylor is the nephew of Lt. Dan, due to their shared last name, military backgrounds, and remarkable resemblance.
  • There is a popular theory that The Prisoner (1967) is a continuation of Danger Man, because the two have similar protagonists, both played by Patrick McGoohan (who cancelled the former to star in the latter), and one episode of The Prisoner, "The Girl Who Was Death", is an unused Recycled Script from Danger Man.
  • Despite the fact that they are Mutually Fictional in canonicity, fans of Psych and Leverage share the idea that Shawn and Eliot are cousins, mostly due to the fact that they have the same last name: Spencer.
  • St. Elsewhere's twist All Just a Dream ending has resulted in a massive crossover theory called the "Tommy Westphall Universe" or the "Tommyverse" for short. Because some shows had crossovers with St. Elsewhere, those shows must be in the same universe and thus also a daydream; shows that crossed over with those shows, then, are also in the universe, and so on. This theory states that over 400 TV shows are within the same universe as St. Elsewhere.
  • Victorious:
    • Henry Danger and Victorious are both in the Nick Verse, so a common theory is that Frankini from the former series is Cat Valentine's frequently-mentioned but never-seen brother from the latter series. This is because Goomer from Sam & Cat appears as Frankini's henchman in his debut episode and mentions that he used to hang out with Frankini's sister. Frankie is also played by Frankie Grande, the brother of Cat's actress Ariana Grande. Frankini's hammy supervillainy also lines up with the strange, psychotic personality Cat describes her brother to have. It's never confirmed if Frankini's sister is Cat, but the implications seem to line up.
    • Another theory about Cat's brother, albeit one with less evidence, is that he's Crazy Steve from Drake & Josh, which is also (inconsistently) in the Nick Verse. This is mostly just because Steve is Ax-Crazy and constantly screaming, lining up with Cat's brother being insane.
    • Robbie being related to Fran from The Nanny, as Renée Taylor played Fran's mother Sylvia in The Nanny and later appeared as Robbie's grandmother, complete with an Actor Allusion or two (Robbie's grandma is also named Sylvia). If Robbie is Fran's son (Fran and Max had boy/girl twins at the end of the original series, and Robbie has a sister), it may explain why Robbie could afford to go to Hollywood Arts as his dad would be a famous producer.

    Multimedia Works 
  • Batman: Creature of the Night is a miniseries about a man who starts to see an apparition looking like his favorite comic book hero, Batman, which can interact with real world and reacts to his subconcious desires, with horrifying results. Many fans of JoJo's Bizarre Adventure like to say it is stealthily set in world of the manga and the "Batman" is actually a highly independent Stand.
  • Marvel Cinematic Universe:
    • Some fans of WandaVision like to believe that Ralph Bohner is actually Pietro Maximoff/Quicksilver from the Fox X-Men Film Series (which was Exiled from Continuity for legal reasons), and is Jimmy Woo's missing person.
    • There are fans of the MCU and The West Wing that consider Mike Casper to be none other than Phil Coulson given that they are played by the same actor and share the same role as government agents, as well as the having the same personality. There are even entire fanfics that have Casper and Coulson be one and the same. Once Clark Gregg learned about the theory, he was delighted and gave it his full approval.
    • Likewise, another theory suggests that Jules Winnfield from Pulp Fiction is Nick Fury. Similar to the Coulson theory, this usually stems from the fact that both characters are portrayed by Samuel L. Jackson. Not to mention that Fury's fake tombstone in Captain America: The Winter Soldier, which is inscribed with a quote from the Bible (Ezekiel 25:17), is the same verse used by Jules Winnfield.

  • Officially, all the campaigns of The Adventure Zone are completely separate from one another. However, fans like to link them up in Fanon.
    • One popular joke is that Balance exists as a fictional podcast within the world of Amnesty, which was given a Fandom Nod in the 2020 Halloween special, where Aubrey (from the latter) dresses up as Magnus (from the former).
    • A lot of fans headcanon that Balance is linked with Graduation by having Gordy's adoptive parents be the liches Barry and Lup. Given that Gordy was abandoned for having necromantic powers, and was later adopted by loving parents who encouraged and nurtured his abilities, it makes sense.


    Video Games 
  • Some fans like to think that Among Us and the Henry Stickmin Series take place in the same universe (or multiverse, if the Omega Ending in Completing the Mission is anything to go by), mainly due to being made by the same company and multiple references in both games.
  • Fans of ANNO: Mutationem and VA-11 HALL-A have considered both games share the same universe with two major characters from the latter making The Cameo and being familiar with the setting of the former.
  • BioWare fans like to believe that the developer's two major franchises, Dragon Age and Mass Effect, are connected, with Thedas simply being another planet in the Mass Effect universe. The fact that there are a lot of Easter Eggs and Shout-Outs in both series certainly helps.
  • As both games involve anthropomorphic bugs, it is common for fans to consider that Bug Fables and Hollow Knight are part of the same universe. Typically, Hallownest is considered to be located in caverns under Bugaria.
  • Capcom:
  • It is commonly believed that the player character of Friday Night Funkin' is the brother of Hatsune Miku, as both are blue-haired singers with an electronic voice. Further fueling the fans are the creators of Friday Night Funkin' jokingly calling it canonical.
  • Due to shared focus on ultraviolence, taking place in an Alternate History version of the Cold War era, big involvement of Russian mafia in the plot and similiar soundtrack, many fans believe Mother Russia Bleeds takes place in Hotline Miami universe.
  • Nintendo's Metroid and F-Zero franchies are both set in a Space Opera future governed by a Galactic Federation, with bounty hunters as main characters. Thus, they could exist within the same universe as each other.
  • Obsidian Entertainment:
    • Fans have headcanoned that The Outer Worlds shares the same universe as Fallout: New Vegas due to both being made by the same studio and taking place in a Retro Universe (The Outer Worlds' setting being modelled after The Roaring '20s and Fallout's taking place in one modelled after 50s-era America). Specifically, it is speculated that the former takes place in the future following the latter's Mr. House ending, due to the Advert-Overloaded Future of the setting pairing with Mr. House's hyper-capitalist leanings delightfully well.
    • There's a bit more to this one. Outer Worlds lore references a catastrophic "Great War" in the mid-21st century. Meanwhile, Fallout lore puts that exact same event in the year 2077. The two colony ships, Groundbreaker and Hope, also both depart Earth in the 23rd century, putting the launch close to the events of Fallout 2, 3, and New Vegas. Hope is even explicitly said to have launched in 2285, not so far away from the year that New Vegas takes place (2281).
    • Due to sharing a theme of criticising late-stage capitalism by showing exactly how would colonization of space under guide of mega corporations look like, most of fans of Hardspace: Shipbreaker seems to agree the game takes place in the same universe as The Outer Worlds. Sometimes this is expanded to also include one of multiple other games where topic of corporations (mis)handling colonization of space is present, such as Citizen Sleeper, Red Faction, Satisfactory, Subnautica, System Shock and Tacoma. It may even reach outside of video games, usually pulling in The Murderbot Diaries.
  • After a review called Pizza Tower as "Celeste for weirdos", the two fanbases became Friendly Fandoms over how odd a comparison they found this (they're both Platform Games, and that's about as far as the similarities go), leading to loads of crossover fanart and a popular headcanon that Peppino is Madeline's uncle.
  • The YouTube channel Dimension Bros theorized in a video that almost all of the seemingly unrelated adventures in Poptropica take place in the same timeline. However, they made exceptions for the sponsored Islands and ones that are too meta.
  • A few people have speculated that two or all of the Spyro series are set in the same universe, thousands of years apart from each other. Commonly cited evidence is that the repaired planet from the end of Dawn of the Dragon (which was split into many floating islands) looks suspiciously similar to the Dream Weavers' homeworld and/or Skylands.
  • Almost immediately after Triangle Strategy was announced, fans jumped on the idea that it takes place in the same world as Octopath Traveler, just on a different continent, due to their very similar art styles. The idea became even more popular after its release because both games use the term "Aelfric" and Triangle Strategy's setting is extremely isolated, meaning it could easily be one of the unexplored lands that are occasionally mentioned in Octopath Traveler. Various Daylife also quickly found itself included in this fanon setting, again due to the use of the term "Aelfric".
  • When the Game Grumps played Zombie Claus and noticed the house map in the game was identical to the one used as Madison's house in the H-Game House Party (2017), they acted like it was the same house, remarking that it would be difficult to return to House Party and not be afraid of a zombie Santa Claus hiding somewhere. Fan theories in the video's comments included that Zombie Claus was punishing the House Party protagonist for being too naughty during the party, or it was just Frank in a costume chasing after you for drinking alcohol.

    Web Animation 
  • The Walten Files: Since the series — inspired by Five Nights At Freddys and Analog Horror videos by creators such as Squimpus McGrimpus — first emerged on YouTube, many viewers believed that the eponymous rabbit mascot of the in-universe Bon's Burgers restaurant chain is not just an Expy of Bonnie from FNaF, but also is none other than Bonnie himself. More specifically, that Bonnie is actually a Canon Immigrant to the mascot cast of Freddy Fazbear's Pizza, and that Bon was his original incarnation in the past. This was later jossed by the series's creator in a community announcement; Fazbear Entertainment does exist in the continuity of The Walten Files, but has nothing to do with Bon's Burgers nor is it plagued by the tragedies and supernatural events of the canonical FNaF continuity. As such, Bon and Bonnie are, and will be two entirely separate characters with no relation to one another.

    Web Original 

    Western Animation 
  • Cartoon Network:
    • There is a longstanding niche fan theory that Greg of Over the Garden Wall grew up to become Greg Universe, as both are musically inclined brunettes that deeply care for their family, and much of Steven's personality coincidentally mirrors OTGW Greg's. The theory is immediately broken due to Halloween, which Over the Garden Wall takes place on, not existing in Steven Universe (confirmed by a joke about "some kind of candy-givin'-out holiday"), though most tend to ignore that since that can easily be overlooked.
    • It's commonly believed that Over the Garden Wall and Clarence take place in the same town due to a few Easter Eggs between the two, the most obvious being a full shot of the town in OTGW being reused from Clarence with a few modifications.
    • A large number of fans believe Samurai Jack takes place in the same universe as The Powerpuff Girls (1998). (As well as Dexter's Laboratory to a lesser extent.) Apart from the obvious fact that both shows had Genndy Tartakovsky involved in their production, much of this is due to how the ruins seen in the first episode of the former appear to resemble a post-apocalyptic Townsville — the main setting of the latter — as well as the identical resemblance between the eponymous Jack and Professor Utonium, leading many to think Utonium is the future descendant of Jack.
  • Due to sharing the same creator, many believe that Danny Phantom and The Fairly OddParents! share a universe. Building on this is the common fan theory (that was at one point going to be canonical) that Danny and Timmy are related.
  • Many fans of DuckTales (2017) and Wander over Yonder like to think the two happen in the same universe; Wander Over Yonder is just set in space so there's no direct communication between the characters. Besides shared creators, the biggest smoking gun is Webby's mention of something called an Oblivion Mirror (also the name an artefact from one episode of Wander Over Yonder) in the pilot. However, fans have also noticed strong similarities in design between Lord Dominator in Wander Over Yonder and the Moonlanders introduced in Season 2 of DuckTales — which, combined with Word of God on Wander Over Yonder that Dominator came from a different galaxy and the refusal to give out her actual planet of origin and birth name, raises the possibility that she was a Moonlander who had better luck than General Lunaris at leaving the Moon and becoming an interplanetary conqueror.
  • Gravity Falls:
    • It is assumed that the show and Rick and Morty are, if not in the same universe, then at least the same multiverse, due to the creators being friends and the countless number of Gravity Falls references in Rick and Morty. There was also an inter-series Brick Joke shared by both shows, in which several objects get sucked into a portal in Gravity Falls, and then identical objects are seen coming out of a portal in Rick and Morty.
    • Gravity Falls is also commonly assumed to share a universe with Over the Garden Wall, due to similar aesthetics and dark, mature themes. A common theory is that Wirt and Greg are related to Dipper and Mabel somehow.
    • Another series with which Gravity Falls is commonly portrayed as being in the same universe is The Owl House, partially due to the Production Posse involved with both shows, but also because of the Crossover Ship of Stan/Eda gaining popularity. Stan's known to have gotten married in Las Vegas to a woman who sounds very similar to Eda, leading many fans to speculate that it was Eda, albeit using a fake name. The creators didn't deny it when asked, meaning this might be the one Vegas crossover theory with canonical support. An episode in the second season even confirms that Eda has used the alias "Marilyn," which is known to be the name of Stan's ex. It's hard not to believe the creators weren't giving the proponents of this theory a wink there.
    • Similarly, Gravity Falls is also portrayed as sharing a universe with Amphibia for the same reasons as The Owl House, and it certainly helps that the latter had a spiritual crossover with the former via Alex Hirsch appearing as frog versions of Grunkle Stan and Soos in one episode. The references would continue in Season 3, where a character is shown wearing a Romance Academy 7 shirt, followed by a Grunkle Stan head appearing a few episodes after that. In addition, a Lil Gideon doll makes an appearance during the season's opening.
  • My Little Pony: Friendship Is Magic:
    • Some fanfics attempt to merge previous iterations of the show with this generation. The first version, My Little Pony 'n Friends, is one of the more common ones; typically, the events of the latter series are depicted as the ancient past of the former, with its characters being legendary historical figures.
    • Discord was voiced by John de Lancie, the actor who plays Q from Star Trek, and Discord and Q are both tricksters with extreme superpowers. Because of this, some viewers speculate that Discord is Q.
  • The Magic School Bus: Because Mrs. Frizzle is sometimes implied to be Really 700 Years Old and her bus can change shape, some people have wondered if she's a Time Lord from Doctor Who. While an episode with a "Fantastic Voyage" Plot shows that she has one heart, some Expanded Universe material posits that Time Lords have a single heart prior to their first regeneration.
  • Primal (2019) is sometimes speculated to take place in the same universe as Samurai Jack, due to the shows (again) sharing a creator and the presence of dark magical elements in both shows:
    • It's a common suggestion that Aku is behind the rage-inducing potion in "Rage of the Ape-Men", the eponymous zombie plague in "Plague of Madness" and the witches' magic in "Coven of the Damned" (with the leader of the coven supposedly being a daughter of Aku).
    • Spear, the caveman hero of Primal also shares some physical resemblance to Samurai Jack and is speculated to be his ancestor.
    • The rage-inducing potion also turns the user's skin purple, indicating it may be the source of Crunk's powers.
  • Fans theorize that Ready Jet Go! takes place in the same universe as Molly of Denali, mostly because Trini (who has the same voice actress as Sydney in Season 2) believes aliens exist, and Jake bears a striking resemblance to Sean, meaning that Sean moved to Alaska and changed his name because he got tired of Mindy's teasing, or Jet cloned Sean and sent it to Alaska. Dinosaur Train is an In-Universe show in Jet if "Mindy's Weather Report" is anything to go by.
  • Some people think that Rugrats and The Loud House take place in the same universe, because in the Loud House episode "Linc or Swim?", there's an old man in the background who's modelled on Grandpa Lou.
  • Many people believe that Total Drama, 6teen and Stōked take place in the same universe due to the focus of all three shows being based around teens, each show sharing the same production company, much of the cast having worked on at least two of the shows (notably Jennifer Pertsch and Tom McGillis, who created all three shows), and how the three shows have been known to reference each other. Sometimes, Grojband is thrown in as well, due to being also produced by Fresh TV (but created by Todd Kauffman and Mark Thornton instead). Additionally, people like to lump the older Clone High (a series with zero production connections to any of Fresh TV's shows) with the aforementioned shows, as the art style of Total Drama was deliberately based off it.
  • Due to Tuca & Bertie sharing the same artist and much of the same Production Posse from BoJack Horseman, as well as also starring Funny Animals, some fans speculated that they took place in the same universe. However, Lisa Hanawalt Jossed this theory prior to the show's airdate, as Tuca takes place in a Denser and Wackier world than BoJack, which became clear when the show aired.

In-universe examples

    Western Animation 
  • BoJack Horseman: Since Reginald VelJohnson plays both Sergeant Al Powell in Die Hard and Carl Winslow on Family Matters, Todd believes they're the same person, with Carl Winslow being Powell's alias under witness protection following the events of the first two Die Hard films.
  • The Simpsons: In the beginning of "Three Men and a Comic Book", while Marge drives Bart and Lisa to the comic book convention as they discuss comic books, the two siblings notice the resemblance between Richie Rich and Casper the Friendly Ghost, and come to the conclusion that Casper is the ghost of Richie after the latter committed suicide.