History AdaptationExplanationExtrication / LiveActionFilms

** The original ''X-Men'' trilogy might leave some viewers wondering how Professor Xavier can afford a sprawling Westchester mansion with its own stealth jet--since he has no apparent source of income, and doesn't appear to charge tuition to his students. The comics explain that he's the heir to a vast family fortune, and the mansion is an ancestral manor that's been in his family for five generations.[[note]] May overlap with AdaptationInducedPlotHole, since the movies' version of Xavier appears to be ''British'', yet somehow apparently inherited a mansion in upstate New York.[[/note]]
** The movies' portrayal of ComicBook/{{Cyclops}} keeps most of his notable traits from the comics, but they omit his backstory, leaving most of those traits unexplained. In particular: he's shown to be much closer to Professor Xavier than the other X-Men, and he [[BlessedWithSuck can't control his optic blasts]] (forcing him to wear his ruby quartz glasses constantly). The comics explain that he lost his parents in a plane crash when he was a child, and the Professor is [[ParentalSubstitute the closest thing he has to a father]]; he suffered significant brain damage in the crash, which left him permanently unable to control his powers when they manifested.

** ''Film/XMenDaysOfFuturePast'' is rather vague about why the Sentinels conquered all of humanity in the film's BadFuture, despite being designed solely to hunt and kill Mutants. The comic book storyline explains that it was a twisted case of GoneHorriblyRight: Bolivar Trask programmed his robots to stamp out the Mutant race by any means necessary, but didn't consider how many ordinary humans carried the "X-gene" that causes mutation; the Sentinels proved to be a little too good at their jobs, and eventually began building concentration camps for processing and detaining all humans with the X-gene.

** Besides the powers, the symbiote is supposed to retain the memories of the previous user. That's how Brock learns Spider-Man's secret identity and stuff like Mary Jane being important to him. Again the movie fails to establish these facts, so the climax feels even more tacked on.

** The issue of Aragorn as heir to the throne of Gondor. If Boromir can recognise the heir of Isildur simply from the name 'Aragorn', then why isn't he king already? In the books, the issue is far more complicated; while Aragorn is the only surviving heir, he's only distantly related to the old Kings of Gondor, and he also comes from a line that had previously been excluded from the Gondorian succession. In fact, he's technically the heir of ''Arnor'', Gondor's northern counterpart that fell many centuries ago, which is only obliquely mentioned or implied a few times in the films. Gondor's line of kings actually descends from Anárion, Isildur's brother--meaning that Aragorn's claim to the throne is actually based on a lineage that split off three thousand years ago. (Arnor's last king, Arvedui, did have a valid claim on the throne due to having married Fíriel, but his claim was rejected due to Arnor's dire state at the time.) The movies explained this as Aragorn himself being reluctant to become king, for fear of falling to petty evil the same way his ancestor Isildur did.

** In the novel, Bob and friends freak out and get angry because Barris brings home an 18 speed bike he bought from someone, but Luckman only counts 9 gears (6 in back, 3 in front), leading them to think Barris got ripped off. Later, when Bob gets debriefed by his superiors, he's told that they're pulling him out because the drugs he uses while undercover are starting to affect his brain too much. They saw the group's reaction to the bike gears, due to the house being under surveillance, and they explain to Bob that the problem was that the group was adding the two sets of gears instead of multiplying them, which is how multiple speed bikes work. Bob's inability to figure out the problem indicates to them that his cognitive faculties are being eroded along with the other users. In the movie, this is not brought up in the debriefing, and the bicycle scene remains somewhat bizarre and unexplained.
** In a scene where the characters are riding in a tow truck after their car broke down on the highway, Luckman says "If I'd known it was harmless, I would have killed it myself." In the book, the statement is explained via {{Flashback}} as an in-joke among the group about how different classes of people view the world differently.[[labelnote:More detail]]At one time they hung out with a rich girl because she'd buy them drugs they normally couldn't afford, and she hung out with them so she could [[SlummingIt pretend she was part of the drug culture]]. One day she saw a bug crawling on a wall, and asked them to come in and kill it. They explained the bug wasn't dangerous, and in fact it's useful because it eats other bugs. She responded with the aforementioned quote.[[/labelnote]] In the movie, it just sounds like an incredibly random thing to say.

*** This question was compounded when ''Film/JurassicWorld'' established that Isla Nublar did survive in the movie continuity.

* In the 1995 adaptation of ''Literature/ALittlePrincess'', Sara wakes up to find her attic room filled with food, clothing and other luxuries. In the book, these things were brought to her in secret over a number of weeks by Ram Dass, the Indian man living next door, while she slept. In the film, they're just ''there'' with no explanation. Ram Dass is however implied to [[MagicRealism be magical in some way]], as it's also he who [[spoiler: helps Sara's amnesiac father to remember her [[SparedByTheAdaptation (he died in the book)]].]]

* ''Film/StarshipTroopers'', adaptation of ''Literature/StarshipTroopers'' had the Mobile Infantry fighting battles that were ''extremely'' unsound tactically. Infantry, unsupported by armor or artillery, making direct frontal attacks on a numerically-superior enemy? HollywoodTactics at their worst. ''However'', it's also true to the book... sort of. The Mobile Infantry ''did'' operate without armor support, but only because their powered armor suits let the MI itself fill the traditional roles of [[SwissArmyWeapon armor, artillery, and even close air support (up to and including nuclear weapons.)]] When the powered armor was taken out of the movie, the justification for the MI operating unsupported went with it.

** The issue of Aragorn as heir to the throne of Gondor. If Boromir can recognise the heir of Isildur simply from the name 'Aragorn', then why isn't he king already? In the books, the issue is far more complicated; while Aragorn is the only surviving heir, he's only distantly related to the old Kings of Gondor, and he also comes from a line that had previously been excluded from the Gondorian succession. In fact, he's technically the heir of ''Arnor'', Gondor's northern counterpart that fell many centuries ago, which is only obliquely mentioned or implied a few times in the films. Gondor's line of kings actually descends from Anárion, Isildur's brother--meaning that Aragorn's claim to the throne is actually based on a lineage that split off three thousand years ago. The movies explained this as Aragorn himself being reluctant to become king, for fear of falling to petty evil the same way his ancestor Isildur did.

* ''Film/TopGun'': For an "adaptation" from RealLife, the WhatTheHellHero speech that Viper gives Maverick and Goose after his first training flight against Jester. The film fails to fully explain why Viper is angry at Maverick for pursuing Jester below the hard-deck: it makes it sound like Jester was trying to be a RulesLawyer. Under real air combat training rules, going below the hard-deck is equivalent to ''crashing''--the hard deck is meant to represent the ground--meaning that Mav won the encounter by default when Jester went below 10,000 feet, but chose to pursue him for an air-to-air kill anyway because of his ego (which possibly implies that Viper and Jester were trying to bait Mav into breaking a rule so they'd have an excuse to take him down a notch).

** [[ColorCodedForYourConvenience The significance of various colors]] was always a central part of the Oz mythos in the books, as Oz was portrayed as a society built around the celebration of color and beauty. This is why some of the most iconic elements of the story are instantly identifiable by their color: Dorothy wears [[IconicOutfit a blue gingham dress and red ruby slippers]] [[note]]Though they were silver shoes in the book[[/note]], she travels along a yellow brick road to reach a city of green emeralds, there's a deliberate shot of a red brick road that leads in the opposite direction from the yellow brick road, and [[DeliberatelyMonochrome scenes in Oz are filmed in color while scenes in Kansas are filmed in monochrome]]. The movie retains the original book's striking use of color, but it generally doesn't explain ''why'' the various colors are significant. In the book, the Munchkins instantly trust Dorothy because she wears blue, which is the color of Munchkinland; various characters assume that Dorothy is a witch because her dress is patterned with white checks, and only sorceresses wear white; the Yellow Brick Road is yellow because it leads to Winkie Country (the land west of Munchkinland ruled by the Wicked Witch), whose color is yellow; the Red Brick Road in Munchkinland leads to Quadling Country, whose color is red; and the Emerald City is green because it's an independent capital city that lies at the center of the four regions of Oz, and thus has its own color.

** In the book, Bill the Pony is much more fleshed out as a character. The Hobbits buy him (for three times his value) after their own horses are set free while they're staying in Bree. His poor health improves in Rivendell, and when the kraken-like creature in the lake outside Moria attacks, Sam thinks BIll is killed by it, and grieves for him. In the movie, Sam sets Bill free before they get to Moria, and appears like he was just really attached to the animal for no real reason.

* When Creator/StanleyKubrick adapted ''Film/TheShining'', he did this with several plot points. Kubrick cut out the explanation of who "Tony" is, the story of the dead lady in the bathtub, and the story of the fellow in the dog costume that Horace Derwent debases--but he left all of those moments in the movie, without explanation. He also revised the story's climax, cutting out the exploding boiler, but still took care to show the boiler in a couple of scenes. It's fairly likely that the absence of explanation for most of these elements was deliberate, though, [[Administrivia/TropesAreTools since the lack of exposition adds to the film's mystery and ability to shock the audience.]]

* ''Film/BladeRunner'' is loosly based on the novel ''Literature/DoAndroidsDreamOfElectricSheep'', where it was a major plot point that most of the world's animals have gone extinct; the novel explains that owning live animals is a popular social trend, and people regularly buy robotic facsimiles of animals if they can't afford real ones. The movie doesn't really explain this, but keeps a couple of references to it. For example: Tyrell owns a robotic owl, and Zhora uses a robotic snake in her dance act (commenting ''"If I could afford a real snake, do you think I'd be working here?"'' when Deckard asks if it's real). One of the questions in Rachael's Voight-Kampff test also hinges on the idea that collecting dead butterflies would be a sick thing for a child to do, while another hinges on the fact that owning calfskin items is illegal.

* ''Film/BladeRunner'': [[Literature/DoAndroidsDreamOfElectricSheep The book]] made a big deal about how real animals have almost died off and everyone is socially obliged to own one to show off their "empathy". The movie doesn't really explain this but keeps a couple of references to it -- the artificial owl and someone's reaction that collecting (and killing) butterflies would be a sick thing for a child to do. The latter especially is a bit random without the explanation.

** It's explained in the book that the White Witch's Turkish Delight is [[VerySpecialEpisode instantly addictive]], making Edmund's betrayal over a supply of candy seem far less petty.

** The 1939 film version portrays the Winged Monkeys as the unquestioningly loyal servants of the Wicked Witch of the West, but never wastes any time explaining ''how'' they came into her service (the fact that they're her {{Mooks}} is presumably enough explanation for most people). But Creator/LFrankBaum's original novel, ''Literature/TheWonderfulWizardOfOz'', specifically explained that the Monkeys were bound to obey the Witch's commands because she possessed a magical golden cap that gave her power over them. It also explained that they ''weren't'' technically her Mooks, as they were only required to obey three commands from the bearer of the golden cap; the Witch used up her last command when she had the Monkeys capture Dorothy and her friends.

** The issue of Aragorn as heir to the throne of Gondor. If Boromir can recognise the heir of Isildur simply from the name 'Aragorn', then why isn't he king already? In the books, the issue is far more complicated; while Aragorn is the only surviving heir, he's only distantly related to the old Kings of Gondor, and he also comes from a line that had previously been excluded from the Gondorian succession. The movies explained this as Aragorn himself being reluctant to become king, for fear of falling to petty evil the same way his ancestor Isildur did.

* The film adaptation of ''Literature/{{Timeline}}'' foregoes the language difficulties presented in the book. In the book, the medieval characters speak a mixture of Middle English, Old French, Occitan and Latin, with the time travelers needing earpiece translators to understand them while they themselves struggle to be understood. In the film, the medievals simply speak modern English and French and have no trouble understanding the time travelers.

* David Lynch's adaptation of ''Film/{{Dune}}'' is one big mess of this. Hardly anything is given a proper explanation, and the film even features a few setups to plot threads whose payoffs are not included.