When an adaptation of a work is made, writers often make changes to the plot. One way of doing this is by giving a reason for something that was not explained in the original. This usually happens in works that have Adaptation Expansion, where the story in the adaptation is longer than in the original work. Sometimes this is done to avoid a Plot Hole.
This happens a lot with book adaptations of films, where we get a look at the characters' thought processes concerning their actions and extended scenes. The book may be adapted from an early draft of the script, and hence may include explanations and details that ended up being cut from the movie for the sake of pace or brevity (or changed, just to confuse the issue). The tabletop roleplaying game adaptation of a film or book will often include huge amounts of explanation or expansion, because player-characters and scenario plots may want to poke around areas of the setting that didn't feature much in the original. Compare All There in the Manual.
Can overlap with Cerebus Retcon if the explanation is dark.
Named by the Adaptation is a subtrope, where the adaptation gives a name to someone or something that was unnamed in the source material.
The opposite of this is Adaptation Explanation Extrication, where the original work explains the plot point, but the adaptation doesn't.
- Ace Attorney: This happens in "Reunion, and Turnabout" (the second case of Justice for All). In the case, Phoenix's friend, Maya, who is a spirit medium, is accused of murdering her client while being possessed by a spirit she was supposed to channel. Turns out the girl she was supposed to channel, Mimi Miney, was actually alive and killed the client to keep it a secret, while Maya's aunt Morgan, whose help was necessary to pull this off, wanted Maya framed to get the position of the master of their clan. This, however, leads to Fridge Logic: While Mimi had much to lose if it was found out she was alive, it wasn't as much as a sentence for murder, and if she didn't know what kind of person Morgan was, how did she know she wouldn't turn her over to the police the moment she asked her for help with the murder? The anime version of events explains this: She didn't. Mimi's plan was to bribe Morgan into faking the channeling and it was Morgan who made Mimi into an accomplice by threatening to reveal the fact that Mimi was alive. Since Morgan knew that Mimi was desperate to keep it a secret, she knew Mimi would comply.
- In the book A Dog of Flanders, the windmill catches on fire, but there is no explanation given as to how it came about. In the 1975 TV series/1997 movie, the windmill catches fire because Hans forgot to oil the gears, leading to parts of it getting overheated. In the 1992 anime, someone accidentally drops their cigarette while inside, not realizing it needed to be put out. Regardless of how it happened, Nello is still accused of setting the windmill on fire because Alois's father doesn't want a poor boy hanging around his daughter.
- In Squid Girl, it's never explained how Squid Girl is able to lift heavy things with her tentacles despite being so small. The anime adaptation explained that her bracelets can control her center of gravity, making it able to lift heavy objects.
- In The Wonderful Wizard of Oz, the Scarecrow becomes King of the Emerald City after the Wizard departs. The sequel, The Marvelous Land of Oz, introduces the idea that there was a royal family who ruled the Emerald City before the Wizard took over, and when the Scarecrow is deposed by General Jinjur's army, Glinda refuses to help restore him to the throne because he has no more right to it than Jinjur has — even though she approved of him taking the throne at the end of the previous book. In the anime The Wonderful Wizard of Oz, which adapts both books, Glinda explains that when she approved of the Scarecrow becoming King she thought the royal family had died out, and only since then had learned that the rightful heir had been hidden away but was still alive.
- Total Drama
- Total Drama All Stars Rewrite: Owen and Noah's reasons for continuing to star on reality TV (as mentioned in The Ridonculous Race) are explained here as the result of Chris making them do so in exchange for giving them more money to help Noah fund Dawn's animal shelter.
- Predator And Prey: Due to the story expanding upon the events of World Tour by showing what happened off-screen, there's plenty of this.
- Bridgette's feelings for Alejandro are explained to be the result of Alejandro raping her during the flight to Egypt, which causes her to develop Stockholm Syndrome (rather than simply just Bridgette being unable to control her hormones as the show implied).
- Bridgette's apology song is explained here as being written by Trent to help her with winning Geoff's heart back, since he and Justin both believe she would never have willingly cheated on Geoff and thus side with Bridgette when Geoff breaks up with her.
- Noah's Ship Tease moment with Bridgette in the Yukon is explained here to actually be him intent on getting closer to Bridgette in an attempt to warn her to stay away from Alejandro for her own good. However, the author speculates that Noah still actually has a crush on Bridgette.
- Ezekiel's feralization is explained here as the result of him getting a brain injury while hiding in the cargo hold when the plane crashed in Jamaica, causing him to lose the ability to speak properly and most of his higher mental functions.
- Beth's inability to answer the question about Duncan in Aftermath Aftermayhem is explained here to be intentional on her part (since Action established that she knows everything about her fellow contestants) as part of the Peanut Gallery's gambit to get rid of Blaineley.
- We also see how the contestants survived the volcano's eruption in the finale of World Tour; they were all rescued by the interns and taken home to Canada safely (except Alejandro, who is left for dead by everyone).
- Fahrenheit 451: In the movie, Montag explains to Clarisse that firemen wear a helmet with the number "451" because Fahrenheit 451 is the temperature at which book paper catches fire. This is never explained in the book and is instead said in the book's tagline.
- Harry Potter:
- In the books, students at Hogwarts tend to be referred to according to their houses ("a first-year Gryffindor" or "a third-year Ravenclaw" and so forth), even though the books are meant to be told from Harry's perspective, and Harry isn't in a position to be keeping track of which house each and every student belongs to. In the films, the Hogwarts robes are given color-coded scarves and neckties corresponding to the four houses, meaning anyone can tell which one a student belongs to just by looking at them.note
- Harry Potter and the Chamber of Secrets explains why Harry couldn't use Parseltongue to communicate with the basilisk when he fought it in the chamber. In the book, he never even tried for no adequately explored reason, but in the film, Riddle immediately dissuades him from doing so by telling him that the basilisk will only obey the Heir of Slytherin. note
- Harry Potter and the Prisoner of Azkaban: In the book, Harry casting the Patronus he'd initially attributed to his father was the result of a random Eureka Moment on his part. The film adds in other cases of future characters influencing past events (Hermione throwing the rocks into Hagrid's hut and howling to distract Lupin in his werewolf form), so that there was a solid basis for his realization there.
- Beauty and the Beast (2017) explains why Belle and her neighbors know nothing about the castle in the nearby woods or about the Prince-turned-Beast: the Enchantress's spell has erased all memory of the castle and everyone who lives there from the outside world. The original fairy-tale has a different explanation (the Prince's family ruled a different land and the enchanted castle wasn't his own, but just his temporary home for the duration of the spell), but in Disney's animated version this is a Plot Hole, which the live-action version fills.
- Interestingly, the live-action adaptation itself has this trope occur, too. Here, the Beast's library contains a magical Portal Book that allows the reader to travel to any location just by thinking about it. The Beast explains that the Enchantress left it as a "cruel trick"—even though he could technically leave at any time, he would still look like a hideous monster and be shunned wherever he goes. That's all well and good...until Belle discovers that Maurice is ill and the Beast decides to allow her to leave the castle to go to him, which is proof that he loves her. Unfortunately, the presence of the Portal Book leaves audiences wondering why Belle simply didn't use it to warp to Maurice instantly, then travel back to the castle with him. That question is answered in another adaptation: The Beast's Tale, the official manga. It's explained that only the Beast can make the book's magic work, meaning he would have to travel with Belle directly into her village to rescue Maurice, which would likely lead to all three being attacked or even killed.
- In the short film Johnny Lingo, it isn't clear why an islander would have the European name Johnny Lingo. The Legend of Johnny Lingo explains that Johnny Lingo's original name is actually Tama, but he got the name from one of his guardians named Johnny Lingo, who in turn got the name from another Johnny Lingo.
- Star Wars: The Force Unleashed novel by Sean Williams not just expanded what we saw and played in the game, also gives The Protagonist (The Apprentice, codenamed Starkiller) a proper name and a background: Galen Marek, son of the late Jedi knight Kento Marek (unnamed in the games and killed in the first episode). His mother is briefly mentioned, but in the novel as well in TFU II got a name and a background too (Mallie Marek, also a Jedi Knight who died when Galek was just a baby).
- Doctor Who Novelisations:
- The novelizations of the first stories from Classic Who added various details to the episodes and even expanded a little more the details that were unexplained, usually written by the same scriptwriters of the series. This helped in actual years to get better help to recreate the Missing Episodes with modern technology, as well using the audiobooks of the time.
- In "The Daleks", the pacifist Thals are under threat of being wiped out by the Daleks but refuse to compromise their ideals, even in self-defence, until Ian proves that they do have things they're willing to fight for by seizing the Thal leader's fiancée and pretending he's going to trade her to the Daleks for his own safety, which prompts the Thal leader to punch him in the face. The TV version never explains how a man from a society that has been entirely pacifist for generations came by the idea of punching people, apparently assuming it to be something that all men know instinctively; the novelization adds a scene in which one of Ian's earlier attempts to bring the Thals around to the idea of constructive violence involved describing and demonstrating the sport of boxing.
- The two-hour episode "The Way of the Warrior" in Star Trek: Deep Space Nine had a minor subplot where Drex and some other Klingons assault Garak on the station and a second one where after the Klingons threaten to open fire on Deep Space Nine they dismiss Sisko's threats as "thoron fields and duranium shadows". The novelization of the episode ties these two together — Drex was assigned by Martok to get intel on DS9's defenses, and Garak figured it out. Garak then provoked Drex and his thugs to beat him up by making them think he had the information. Only Garak had dummied up a fake report by a "Chief Tam O'Shanter" saying that DS9 had minimal weapons and any scans would show false readings.
- In an early episode of Masked Rider, a trio of skull-faced monsters are pointed out to have a weakness to water, and Masked Rider is able to destroy them by tackling them into a lake. This weakness is not mentioned in the original Kamen Rider BLACK RX, where going in the lake just makes them explode for no apparent reason.
- Power Rangers:
- Operation Overdrive: in Boukenger, Gaja's Mooks, the Karths ("Chillers" in OO) are often seen being used by other villain factions without explanation. The OO episode "Just Like Me", which features one such battle from the Sentai version, has Flurious' flunky Norg bring "Chiller stones" to Moltor, which he uses in the fight against the Rangers.
- The first episode of Mirai Sentai Timeranger has a bad Unexplained Recovery moment when the Timerangers are trapped in a crashed ship which explodes with them on it... and are inexplicably uninjured afterward. In Power Rangers Time Force, Trip frees himself and gets the others off the ship before it blows.
- Final Fantasy VII: Machinabridged does this for the original Final Fantasy VII regarding Shinra's plan to use Huge Materia to blow up Meteor. In the original game, no reason was given for the party stopping their plan, making Shinra look like a Designated Villain as a result, as Shinra was still trying to stop a meteor from obliterating the planet. In this version, the party members point out how dangerous blowing up Huge Materia in the atmosphere would be, essentially treating it like detonating a magical nuke, which would lead to horrible aftereffects for the planet, thus giving the heroes a good reason to stop Shinra's plan.
- Beast Wars did this with the "Transmetal 2" toy line, so named because they were the 2nd wave of Transmetal action figures. In the cartoon, they give this an explanation: the Plot Device of the Transmetal Driver is what creates the Transmetal 2 upgrades. However, some of the transformers adopted from the T2 line received their transmetal forms without the driver; thus they're not technically Transmetal 2's even though they're part of the same toy line.