An episode that seems to have no importance to the main Story Arc, only for a major revelation that happens later on in the work to show that it actually held great significance. Basically, it's a Wham Episode that hides its nature as one from the audience.
May use a Chekhov's Gun and related tools, but what really makes this trope is that telegraphing is avoided or downplayed; there is no Rewatch Bonus to be found, as the creator has made minimal-to-no moves to suggest to the viewer that what they just witnessed will have any major plot ramifications. With that in mind, this trope can sometimes be the result of Arc Welding, where a story arc is created retroactively from concepts present in prior, isolated episodes.
Some examples of Jumping the Shark and Franchise Original Sin demonstrate the negative aspect of this trope (minus creators' intention) in which an episode or gimmick that at first appears silly but harmless turns out to be an indicator of future problems with the work.
Compare Wham Episode, where the importance of the events to the overarching story is immediately made clear.
The examples, naturally, contain Major Spoilers.
- The 9th issue of Grant Morrison's run on Action Comics, sandwiched between "Superman Versus Brainiac, Fuck Yeah" and "Superman Versus Captain Comet (While Batman Chuckles At His Secret Identity Problems)" was an interlude involving parallel universes, a Corrupt Corporate Executive who creates a machine of incredible power allowing a monster to enter his world, and a black version of Superman who is the president of his America. The monster, Superdoom, comes to fight the main universe Superman in issues 17 and 18. It also turns out that the machine's creation is the result of events in The Multiversity.
- The 1991 DC Crossover Armageddon 2001 had a bunch of tie-ins that occurred in that summer's annuals. Most of the annuals had standalone stories that had no effect on their main books, but the Superman annual for that year ended up foreshadowing key events in the Super-books, such as Superman deciding to finally take down Intergang once and for all which happened later that year, and Superman leading the rest of the DC heroes against against Brainiac's invasion of Earth in the "Panic in the Sky" storyarc which happened a year later.
- Justice League of America #166-168 from the 1970s features the League swapping bodies with the Secret Society of Super-Villains. No real significance at the time, but the 2000s mini-series Identity Crisis revealed that this incident led the League to start wiping villains' memories (including Doctor Light, whose personality change significantly altered the character), and brought about severe distrust issues among the members of the League which culminated in the group's downfall.
- Grant Morrison's Seven Soldiers of Victory series consists of seven miniseries that all initially seem to be telling different stories, but ultimately overlap. Also, the Leviathan, a monster made up of hundreds of feral kids that appears in one issue of the Klarion mini-series, later turns up in Batman Incorporated as a sinister organization.
- The Flash #134 is a self-contained Jay Garrick story released between two major story arcs. It also marks the first appearance of Jakeem Thunder in a blink and you'll miss it panel where Jay accidentally gives him the pen containing Johnny Thunder's Thunderbolt.
- The Spider-Man arc "I Killed Tomorrow" is a fast-paced, fun beat-the-clock arc rife with humour and energy. The two-issue arc deals with Grady Scraps' invention of a Time Door that allows for travel to and from the future, and neatly wraps itself up at the end. It plays like a "breather arc" in the period between the intensity of Spider-Island and the epic sprawl of Ends Of The Earth. Flash forward to the Superior Spider-Man arc "Necessary Evil", and it turns out this Time Door is the passage through which Miguel O'Hara, Spider-Man 2099, comes to the present day and is subsequently stranded here.
- In Transmetropolitan, Spider Jerusalem goes looking at the Reservations! Warren Ellis gets to write social science fiction! Too bad Spider gets exposed to the substance that leads to his debilitating brain condition...
- Issue 45 of Transformers: More than Meets the Eye is presented as another detour to meet the Necrobot and that it won't have a larger impact on the story. The Necrobot's home ultimately becomes the setting of the season finale and plays a major role in the rest of the series onward.
- "The Corpse" one-shot from Hellboy. The story appears to be a one-off adventure where Hellboy rescues a baby from faeries. The baby would grow up to be Hellboy's Love Interest and one of the faeries, Gruagach, would swear revenge and eventually kickstart Ragna Rok which leads to Hellboy's death.
- Captain Marvel #34 is the first appearance of Nitro, whom Mar-Vell and Rick Jones foil from stealing a nerve gas called Compound 13. The gas canister is ruptured in the explosion, but Mar-Vell seals it again. Everything all right? Wrong. The gas turns out to be cancerous, which leads to Mar-Vell's terminal illness in The Death of Captain Marvel.
- The Bolt Chronicles: The Wedding Reception proves to be the catalyst for shipping Bolt and Mittens in a later fanfic. Made clear in The Ship, where this earlier storys dance between the two characters is referenced as an establishing factor for Mittenss growing attraction to Bolt.
- The New Adventures of Invader Zim:
- Episode 5 seems like just another case of "Dib tries to find an edge on Zim and suffers Epic Fail" like so many in canon. However, his actions cause the senior Swollen Eyeball agents to decide in the following episode to assign Steve and Viera to help him, thus significantly changing the status quo.
- Episode 8 is just filler about Viera and Gaz coming to blows (ultimately literally) due to clashing personalities. But Gaz maintains a serious grudge over this, to the point that come Episode 19 she uses a phone number Norlock left her (also in Episode 8) to tell him and Zim where to find Project Domination just for a shot at payback.
- Self-Discipline from Young Justice: Darkness Falls. The A plot is about the team investigating The Penguin. However, their investigation shows that Intergang is essentially destroyed due to Apokolips cutting off their supplies, and meanwhile on War World, Desaad makes one request to Vandal Savage: None of the metahumans are to be harmed. Both these things would hold great significance down the line for villains and heroes alike.
- The Marvel Cinematic Universe does this frequently, as several of the "smaller-scale" films will still include elements that tie into future arcs:
- Thor: The Dark World is far from one of the critical entries in the series, but The Stinger reveals that the MacGuffin of the film, the Aether, is actually a relic called an Infinity Stone; and so is the Tesseract from prior films. This was when the audience first realized that the whole franchise had an interconnected Myth Arc based on The Infinity Gauntlet storyline (although Thanos appearing during The Stinger of The Avengers at least set the stage for his involvement and he is most frequently connected to the Infinity Gauntlet). The death of Frigga also had an unexpectedly large effect on Thor's and Loki's character arcs, with it being the first major loss of several for Thor that would cause him to develop a guilt complex by Infinity War and the start of the path to a HeelFace Turn for Loki. Even more important after Thor and Rocket travel back in time to the events of this film in search of the Reality Stone in Avengers: Endgame.
- The Guardians of the Galaxy films initially seem like Bizarro Episodes far-removed from most of the things going on in the rest of the MCU, but a lot of what happens in them ties in directly to the overall Myth Arc; especially the discovery of the Power Stone and the full explanation of the Infinity Stones in general, and Thanos' relation to two of the main characters, Gamora and Nebula. It all becomes crucial viewing by the time Infinity War and Endgame roll around.
- The first film also acts as the first real introduction to the cosmic side of the Marvel Cinematic Universe, which up until then hadn't been explored much outside of the occasional glimpse of things happening beyond Earth, and would become more important to the overall plot as the franchise progressed.
- Avengers: Age of Ultron may seem like a Villain of the Week episode at first, but the events of the film have serious repercussions for the MCU, to the point of having a ripple effect (it is the catalyst for virtually everything that makes up the "Phase 3" slate in some form or another). The casualties resulting from the fight in Sokovia leads to the Sokovia Accords being established and the Avengers splitting up in Captain America: Civil War, and the main antagonist of that film lost his family in the battle at the end of Ultron and wants revenge. By the time Infinity War starts, the heroes are still divided, which Word of God says is why Thanos won. Even in more self-contained films like Spider-Man: Homecoming and Ant-Man and the Wasp, and television shows like Agents of S.H.I.E.L.D., the Accords have an impact.
- Doctor Strange (2016) is like Thor: The Dark World in that it has little to do with the rest of the MCU until the very end, where Wong mentions that the Eye of Agamotto holds an Infinity Stone (thereby connecting it to the now-established Myth Arc).
- While Ant-Man and the Wasp is for the most part a self-contained palate cleanser after the events of Avengers: Infinity War, this movie was stated as "the most connected" to Avengers: Endgame. The entire plot of Endgame gets started when Scott comes to the Avengers and explains how the Quantum Realm could potentially fix the problems Thanos caused in Infinity War.
- The eighth Alex Rider book, Crocodile Tears, is largely a Breather Episode. However, it does establish that there has recently been a general election which resulted in a new government being voted in. At the time, this just seems to be a way of inconveniencing MI6, as the new Prime Minister isn't aware of who Alex is and Blunt has to struggle to get Alex's warnings about the Big Bad to be taken seriously. However, the Prime Minister's obvious discomfort with the idea of a minor working as a spy has a big payoff at the beginning of the next book,note where he has forbidden Blunt from using Alex again and decided to have him retired as head of MI6.
- Bridge of Birds: Every seeming Wacky Wayside Tribe turns out to be this by the end.
- The Horse and His Boy at first glance seems to have no effect on the overall plot of the The Chronicles of Narnia series. However, it thoroughly establishes the Calormenes, a throwaway reference in The Voyage of the Dawn Treader, as the Evil Empire; and it contains a chilling Foreshadowing of how the Calormenes will figure in The Last Battle: "On this venture you are to regard every drop of Narnian blood as more precious than a gallon of your own. On this venture, I say. The gods will send us a happier hour...."
- In the Dirk Gently series, Dirk's "holistic" philosophy isn't wrong in the context of the books even the aside jokes are relevant later on.
- The Dresden Files:
- Book three, Grave Peril, has serious implications reaching all the way out until Changes. (And likely beyond, as books continue to be released. Word of God says that all the guests at that little party will be seen again.)
- Going back to the first book, Storm Front, the ritual used by Victor Sells is the same one the Red Court wants to aim at Harry in Changes, the twelfth book.
- Harry Potter:
- Harry Potter and the Chamber of Secrets set up Harry Potter and the Half-Blood Prince seven years in advance. It set up the concepts of Horcruxes through Riddle's diary, it introduced the four Hogwarts founders and established Voldemort's connection to the Slytherin bloodline, the basilisk fang from the Chamber would later be used to destroy two of the Horcruxes, and the idea that Voldemort inadvertently passed some of his abilities to Harry would prove to be major foreshadowing for the revelation that Harry was an accidental Horcrux. It introduced Ron's sister Ginny (who would become Harry's primary love interest by Half-Blood Prince), and the concept of "blood purity" and Pureblood supremacy would become major lynchpins of the mythos by the end. And in one scene, Nearly Headless Nick convinces Peeves to destroy a cabinet to distract Filch for Harry; the broken cabinet becomes a major plot point in Half-Blood Prince. Not bad for a work that at first glance looks like a book-long Wacky Wayside Tribe.
- Harry Potter and the Philosopher's Stone seems to be a relatively light introduction to the Wizarding World that ends with all of its loose plot threads tied up. Upon rereading it, though, one realizes how important it really is to establishing the core themes at the heart of the series. The Big Bad fails to kill Harry because of the Magical protection granted by his mother's sacrifice, Nicholas Flamel chooses to die from old age to prevent anyone else from using the Philosopher's Stone for evil, and Voldemort's plan turns out to revolve around getting his hands on the substance that can make him immortal. The theme of death—Voldemort's fear of it, and the heroes' willingness to face it—plays a major role. In later books, it becomes clear that it's also the Central Theme of the series as a whole, and we gradually find out that all of Voldemort's actions are driven by his quest to cheat Death and become immortal. Dumbledore's speech at the end ("To the well-organized mind, death is but the next great adventure,") is a poignant moment, but it takes several more books before we realize how important it really is.
- The Hitchhiker's Guide to the Galaxy sets up a few of them, mostly in the first book. A person is mentioned in the prologue and then dismissed with "but this is not her story"; the same prologue is used in the fourth book, only now it is her story (as well as Arthur's). Then there's Arthur's first encounter with Vogons, in which he says that he wished he had a daughter so he could forbid her to marry one. Four books later, he does have a daughter, and she's quite rebellious—though she and the sympathetic Vogon character introduced in the sixth book never actually meet. Finally, there's that bit about the bowl of petunias thinking "Oh no, not again", and the book says that if we knew why it was thinking that, we might know a lot more about the universe than we do now. We find out the answer in the third book. Notably, Douglas Adams was making it up as he went along, and would deliberately leave threads like these dangling with no idea of what, if anything, he was going to do with them. So when he did tie up a loose end, it was as much a surprise to him as to the rest of us. Another example is the implication from Arthur's encounter with Agrajag in Life, The Universe and Everything that Arthur cannot die until he's been to Stavromula Beta, which doesn't even seem to occur to Adams until two books later, when he has to construct a kind of Shaggy Dog Story (and an incredibly lame pun) to wrap up a loose end he hadn't even acknowledged previously.
- The "Riddles in the Dark" chapter of The Hobbit is revealed to have been surprisingly significant when the reader starts with The Lord of the Rings, partly because Tolkien had to change it to fit the new book's continuity.
- The prologue to A Game of Thrones is like this to the entire A Song of Ice and Fire series. The prologue to A Feast for Crows serves the same function within that book, setting up plot that doesn't truly get put into motion until the last chapter, some 900 pages later.
- The Warrior Cats novel Dark River is one of these. At first it seems to be an interesting romp based on forbidden love, but looking back on it with Omen of the Stars completed and Dawn of the Clans coming soon it's one of the most important books in the series. It introduces the Ancients (the shared root of the Tribe and the Clans), Rock (who is revealed in The Last Hope as the cat who gave StarClan the prophecies), Dark Forest cats entering the real world, and the Tunnels (a massive Chekhov's Location).
- Of all the short stories in The Last Wish, "A Question of Price" is by far the most important one in retrospect after reading the rest of The Witcher saga. On its own, it's just a surprisingly lighthearted romance where a princess undoes the curse of her true love and it ends with their wedding. Their daughter Ciri becomes a major character in the saga and Pavetta's mysterious powers are a major plot point. Finally, Duny turns out to be a lot more than what he seemed...
- Two Percy Jackson and the Olympians short stories, The Bronze Dragon and The Sword of Hades, were included in a spin-off book titled The Demigod Files published before the fifth and final book in the original series. While the short stories have virtually no influence on the story of the original series, they have a massive impact on the sequel series The Heroes of Olympus: particularly, the eponymous bronze dragon becomes the heroes main form of transport in the sequel series, and a reformed titan from The Sword of Hades is vital in helping Percy and Annabeth survive the depths of Tartarus.
- In the Attitude Era, it was told that each of the four McMahon family members owned one quarter of the WWF. And then came 2001. Linda's loss of the WWF stock to Vince during her breakdown, combined with Shane and Stephanie's selling of their stock to purchase WCW and ECW during the Invasion, set up the Brand Extension and the return to the WWF of Vince McMahon's new business partner and co-owner: Ric Flair.
- Who would have imagined that news of a host of WrestleMania 27 would bring not horrors of Justin Bieber, but the return of the Rock after seven years and his year-long feud with John Cena at WrestleMania 28?
- CM Punk's pipebomb would not only elevate him into a true main-eventer, but would also set up the debut of "douchebag yesman" John Laurinaitisnote , plus the fact that he mentioned being a "Paul Heyman guy" would later come into play when Heyman (also aligned with Brock Lesnar) returned at Punk's side after beating up John Cena (and the term "Paul Heyman guy" actually came into use).
- The Magic: The Gathering expansion Mirrodin had a villain named Memnarch, a golem driven mad by a weird, glistening oil. Memnarch was defeated, but the oil remained. It turned out to be Phyrexian oil, heralding the corruption of the plane of Mirrodin into New Phyrexia seven years later.
- For the first Hascon, Magic released a set of cards representing other Hasbro properties. One of these was for Grimlock. One side was a Dinosaur (a then unused type), and it was three color red, green, and white. Since it's silver bordered (non-cannon and not legal in official events), no one thought much of it. But a couple of months later, Ixalan was released, where Dinosaurs were a major theme, and they were in red, green, and white.
- The New World of Darkness core rulebook began with a story about mechanical angels serving the enigmatic God-Machine. While popular, this didn't seem important until ten years later, with the release of the second edition, the God-Machine Chronicle, and Demon: The Descent, both of which involve the God-Machine heavily.
- Red vs. Blue: Pretty much the entire Blood Gulch Chronicles qualifies as this. While these first five seasons were mostly played for comedy, Season 6 used some expert Arc Welding and made even the one-off jokes important. Some major examples include:
- Church's death in Season 1 was originally just a bizarre piece of paranormal humor, but it actually ended up being the main clue that lead to Washington realizing that Church is the Alpha.
- The Season 2 finale had a hilarious joke about both Reds and Blues having the same contact. This is eventually revealed to be because the Reds and Blues were just used as Freelancer target practice.
- One of the biggest instances of this was Season 3's "Let's Get Together", which contained a random joke about there being only forty-nine states and Florida not existing for some reason. Season 10 reveals that this is because the Director sunk Florida so that no one would notice the disappearance of Agent Florida, also known as Captain Butch Flowers.
- Tucker's "quest" in Season 4 actually played an important role in the Chorus Trilogy, as his connection to the aliens helps the people of Chorus gain an upper hand.
- El Goonish Shive: A griffon showed up as a two-panel joke in a comic from 2013, where it's an Offscreen Moment of Awesome alongside a bunch of in-story Flashbacks. Two years later, it turns out that the griffon actually was pretty noteworthy.
- Gunnerkrigg Court seems to be using this heavily, as several chapters, characters and plot points that seemed to have nothing to do with the overall Myth Arc at the time (particularly Aly's transformation in "A Week for Kat") have taken on greater importance later, especially after the events of Chapter 20. Even the second chapter, which looks like filler, contained set-up for what is now confirmed to be an Aborted Arc.
- Homestuck's intermission at first seems to be a completely unrelated, silly tangent that has no bearing whatsoever on the plot. Of course, everything in Homestuck is plot-relevant, and said intermission turned out to have a big impact on the trolls' session, especially after the EOA5 flash when Spades Slick kills Snowman and destroys their universe. In fact, the Intermission includes the first mention of the comic's eventual Big Bad. For some, as much as the first three acts could be considered this, appearing to be nothing more than a bunch of pointless gags, but in actuality setting up a lot for later on such as the bunny John receives as a birthday present, which ends up becoming incredibly powerful, reaching the hands of a villain, and in doing so causes at least half of the terrible things that happen during the kids' and trolls' sessions.