- Evelyn Waugh created an entire style of plotting out of this trope. He would introduce an element, toy with it a bit, then apparently drop it for something else, only to have it reappear later in the narrative as if out of nowhere, to greater or lesser effect. One example appears in Officers And Gentlemen in which a Scottish lord obsessed with explosives attempts to manipulate the protagonist into obtaining some from the British Army. A hundred pages later he hears an officer talking about a Scottish castle that was mysteriously blown up. Waugh's reasoning for this was that it parallels the way life really works.
- A Series of Unfortunate Events: The phrase "red herring" is introduced in The Ersatz Elevator. That is not funny on its own—however, it is still crucial to a Stealth Joke pulled off in The Hostile Hospital. All the names on the patient list are anagrams—one of them, when rearranged, becomes the phrase "red herring".
- Harry Potter:
- Harry Potter and the Philosopher's Stone: Near the beginning, Mrs. Weasley tells the twins that she doesn't want to hear that they've blown up a toilet. George says that they've never done that, but he thinks the idea is excellent. In the final chapter, when Harry is in the infirmary, it's mentioned that the twins tried to send him a toilet seat.
- Upon first meeting Snape, he thinks that it is as if Snape can read minds (he thinks this again in book 2 as well). In book five, we find out that Snape is a master of Legilimancy and Occlumency.
- Early on in book 6, while the trio are having a discussion while doing homework, Ron Weasley's spell-checking quill wears out and corrects the spelling of his name to "Roonil Wazlib", much to Hermione's amusement. About 3/4 of the way through the book, after Harry has hidden his dark-magic-graffitied copy of Advanced Potion Making and replaced it with Ron's, we get this priceless moment:
Snape: This is your copy of Advanced Potion Making, is it, Potter?
Snape: You're quite sure of that, Potter?
Snape: This is the copy of Advanced Potion Making you purchased from Flourish and Blotts?
Snape: Then tell me, why does it have the name "Roonil Wazlib" written inside the front cover?
- This is common with Ron Weasley. When he first introduces Scabbers to Harry in The Philosopher's Stone, he says of Scabbers, "He could have died and no one would know the difference." In Prisoner of Azkaban we learn Peter Pettigrew/Scabbers did just that. In Chamber of Secrets, he jokes that Tom Riddle got his award from the school for murdering Moaning Myrtle. We learn later that's exactly what happened.
- At the beginning of Harry Potter and the Order of the Phoenix, Luna is reading an edition of The Quibbler (a tabloid magazine) that claims that Sirius Black is really a wizard musician called Stubby Boardman. At the end of the book, Harry goes off to rescue Sirius with Ron, Hermione, Neville, Ginny and Luna, and Luna pipes up, "When you say "Sirius", do you mean Stubby Boardman?"
- There's a picture in The Last Straw, the third Diary of a Wimpy Kid book, that reveals that Greg once turned in a book report 4 pages long (cover included), and only a few sentences long because he took up more than half of the last page writing "THE END" in big letters, using the excuse that he was running out of paper. That spoiler-tagged part comes up at the end when Greg admits that he was ending his story on sort of a generic happy ending note, but he admits that he's running out of paper.
- In the first book of the H.I.V.E. Series, the young protagonists spend the entire volume trying to escape the Island. This plan hinges on, among other things, Otto being able to fly a helicopter. When the other characters question this, he insists repeatedly that he can look at any machine and "just know" how to pilot it, the helicopter included. They very narrowly lose the opportunity to leave via helicopter, and in book seven, four years later, the protagonists are learning how to fly helicopters, among other things. It's revealed that Otto is completely incapable of mastering this, and has blown up all of his passengers in simulation on multiple occasions. Had the escape attempt in book one been successful, they would all be dead.
- The world of Harry Dresden drops these sometimes, to great effect. Perhaps the most memorable is in White Night, when Harry has to pose as Thomas' disgruntled lover when he is caught in his apartment, because while he had a key he was breaking in. The policeman called up to handle the situation spreads the story around the station, whereupon Murphy immediately ribs Harry about it the next time they meet. A short time later, they have to visit a—[ahem]—"health club", and find out Harry unknowingly possesses a lifetime membership.
Murphy: What's that all about?
Harry: Don't ask me. I'm gay now, remember?
- In Death Masks, there's a discussion in the narration about how Harry used to stargaze with Ebenezar McCoy when he was living on the old man's farm, and Harry reminisces about how they discovered an "asteroid" that turned out to be an old Soviet satellite. Halfway through the book, Ebenezar calls Harry up and, at the end of their conversation, offhandedly asks where the telescope they used to use got stashed. At the very end of the book, "Asteroid Dresden" falls out of the sky and obliterates a powerful vampire intent on killing Harry, along with his manor house and his thralls, in what may be the first time this combines with Colony Drop.
- In return for his services in Summer Knight, the Wee Folk clean Harry's apartment spotless and bring in a (sometimes questionable) selection of food. He can't tell anyone about them, however, or they won't do it anymore. Skip forward to the novella Backup, told from Thomas' point of view, where he spares a thought to his complete bafflement at Harry's apparent Neat Freak tendencies.
- At one point in the first A Song of Ice and Fire book, Shagga threatens to "cut off [a man's] manhood and feed it to goats." In the next book, Tyrion tells him to do this to a prisoner, despite not having any goats nearby. Shagga obliges, and takes his ax to the prisoner's beard.
- Another is set up from a character's first appearance and takes almost the entirety of three books to land: Lord Tywin Lannister did not, in the end, shit gold.
- In the first book, Catelyn Stark hears the legend of Alyssa Arryn, a mythic figure whose tears were said to have been turned into a waterfall after her death for her unwillingness to shed them in life. Catelyn asks "When I die, how great of a waterfall will the gods make of my tears?" She gets her answer two books later when she is murdered in the Red Wedding and the Trident river overflows in a massive flood the likes of which hasn't been seen in a thousand years.
- Percy Jackson and the Olympians
- In the second book, Sea of Monsters, Percy can't pronounce "Laistrygonians", so Annabeth proclaims the Laistrygonian giants to be "Canadians". Five books later, in The Heroes of Olympus series, this is brought back up in Son of Neptune, where Percy calls them "Canadians" in front of genuine Canadian Frank Zhang. Frank is not pleased.
- Partway through the The Last Olympian, Percy's cyclops half-brother Tyson is having a lunch break with other cyclopes in Poseidon's armory, when a battle going on outside starts getting close, and an outer wall gets knocked down. Tyson promptly picks up a fallen warrior's weapon and yells "For Poseidon!" but it comes out wrong due to his mouth being full of a peanut butter sandwich. The other cyclopes all grab weapons and yell "PEANUT BUTTER!" before joining the battle. Several chapters later, while Percy communicates with Poseidon, Poseidon mentions that "Peanut Butter" is an odd battle cry.
- There were also a few throwaway lines about a lost pizza deliveryman. In its second sequel series set years later, Apollo reveals that he was the one who ordered pizza.
- Wayside School loved this trope:
- When Louis gets all the cows out of the school, someone comments they can still hear a moo. 19 chapters later, it's revealed there's a cow in Miss Zarves's class.
- When they test the theory of gravity, showing that objects fall at the same speed despite different masses, they throw a coffee pot out the window. Much later, Mr. Kidswatter asks where the teachers' lounge coffee pot went.
- When Benjamin reveals he's really Benjamin Nushmut, Mrs. Jewls gives him the lunch that was on her desk from the first day of class.
- In "A Story with a Disappointing Ending", Paul is hypnotized not only into not pulling Leslie's pigtails, but into trying to eat her ears whenever she says the word "pencil". About ten chapters or so after this, Leslie throws the classroom pencil sharpener out the window while learning about gravity, and mentions they'll need a new pencil sharpener...
- Dark Future: Early in Krokodil Tears a news report mention the death of Wally The Whale, last living cetacean in the Atlantic and major tourist attraction for the Isle of Skye. The Mayor of Skye plans to have the whale preserved and open up a restaurant in his stomach named Jonah's Snackbar. Two hundred pages later, during the climactic fight between Jessamyn and the Jibbenainosay, Wally the Whale comes back to life. In the middle of the Bolivian ambassador's birthday party.
- In the Doctor Who Expanded Universe short story collection Transmissions, the story "Only Connect" is about the Fourth Doctor working as a taxi driver and chatting to an architect, in the process learning the weak point of Chase Manor. The architect also mentions that a mad old lady claims the housing estate he's currently working on is being built on a plague-pit and this will awaken the restless dead, but he dismisses this as nonsense and the Doctor doesn't seem interested. The final story of the book involves the Eighth Doctor reliving memories related to all the other stories ... including the time the Fifth Doctor had to fight zombies on that very estate.
- An example of the drama type: in the ninth book of the How to Train Your Dragon series, a seemingly-small mark on Hiccup's forehead called the Slavemark which he gets in the seventh book. It remains dormant in the eighth, but in the ninth, after he wins his swordfighting tournament against his father, wins the crown of King of the Wilderwest and delivers a speech on how the dragons need to be freed so they won't attack the humans, his enemy Snotface Snotlout throws a rock at Hiccup's helmet, showing the Slavemark to everyone, forcing him to join the other slaves and throwing the Barbaric Archipelago into turmoil.
- Star Trek: Deep Space Nine Relaunch: At the conclusion to The Left Hand of Destiny, Chancellor Martok promises to repay a debt to his comrade/valet Pharh by sending a Sporak ground vehicle to Pharh's family on Ferenginar. In a later novel, Worlds of DS9: Ferenginar, a destitute Brunt gets a job driving a Sporak on Ferenginar...a Sporak which the owner insists was paid for by the Klingon chancellor, a claim Brunt finds dubious.
- Discworld loves its brick jokes. Some play out within the same book, but some play out in later books. In Men at Arms, the sign on the post office has missing letters, for example "GLO M OF NI T" (instead of "gloom of night"). In Going Postal—eighteen books later—the protagonist notices the missing letters and gets to the bottom of it.
- At the beginning of the first book in The Bartimaeus Trilogy, the title character explains that he has multiple conscious trains of thought (as opposed to humans, which only have one), hence the Footnote Fever used in his sections of the narrative. This isn't mentioned again until the last book, in which he's Sharing a Body with a human. As he goes off on yet another footnoted tangent, he is interrupted by that human, who heard both thoughts simultaneously and found it very disorienting.
- The Twits: Turns out the Shrinks is a real disease you can get from being upside-down for too long.
- In Little Women, Jo March gave a dinner party where she messed up the cooking. Several years later, in Little Men, when Jo, Meg, and Laurie are now married with children of their own, they laugh over that dinner party again when setting up Daisy's toy kitchen.
- The Mammy combines this trope with Stage Names. Agnes sends her boys to collect a pension cheque from the hotel where her recently deceased husband worked and they cause havoc before being helped by a guest called Harry Webb who gave them tickets to a show to give to their mother. When she learns who they got the tickets from, she faints in shock. It's stated on the very first page that Agnes Brown is a massive fan of Cliff Richards and part of the story is her trying to go to his concert. Guess who Harry Webb is more commonly known as?
- In the first Origami Yoda book, Kellen gets water on his pants, and asks Lance to tell people that it's not actually pee. Lance replies, "What am I supposed to do? Follow you around and tell people, 'It's not pee, it just looks exactly like pee'?". 5 books later, Lance accidentally gets dew on Kellen's pants, and Lance jokingly says to Kellen, "It's not pee, it just looks exactly like pee!". The dew incident happened in front of everyone, so Kellen is not amused.
- The Hitchhiker's Guide to the Galaxy series:
- Early in Mostly Harmless, we're told about Ford's principles, one of which is opposition to cruelty to all animals except geese. Much later, he calls room service in a hotel and asks them to buy London Zoo on his behalf, release all the animals that would be able to make it in the wild, and find more natural surroundings to care for the ones that wouldn't. Oh, and all the fois gras they have.
- In the first book, a bowl of petunias falls to its death and thinks "oh no, not again!". It is not clear what that means, until the third book of the (5 book long) trilogy, Life, the Universe and Everything when it turns out the bowl is the umptieth reincarnation of a creature that in all its incarnations gets killed directly or indirectly because of something Arthur Dent did.
- Fenchurch, Arthurs Love Interest in So Long, and Thanks for All the Fish, turns out to be the girl in the cafe in Rickmansworth who had discovered the solution to all the world's problems.
- At the beginning of Warprize, Keir remarks that the best part about being a warlord is "getting exactly what you want." By the finale, the protagonist has risen to a similar position of power, and muses that he was right.
- In Greg Egan's novel Schild's Ladder Yann (a software entity) and Tchicaya (a human cyborg) are discussing the old slander about software entities wanting to turn the whole universe into a giant computer, and Yann dismisses it by asking why "indolent fleshers" haven't yet turned the whole universe into chocolate. By the end of the book we have learned that the team of researchers at Mimosa Station, including Yann, accidentally initiated a collapse that's in the process of turning the whole universe into a giant computer.
- In the Goosebumps book It Came From Beneath the Sink, the "Encyclopedia of the Weird" is consulted to identify the titular creature. When it is mentioned that the monster is a Grool, it is pointed out on the bright side it's not the more dangerous Lanx. At the end of the story, the protagonist is confronted with a Lanx.