In the book, Alice tells the Blue Caterpillar that she was attempting to recite a poem earlier, but the words came out wrong (she does this while she's in the hall of doors). But in the movie, Alice didn't do this, making nonsense out of the line where she tells the caterpillar she did this.
In the book, Alice first sees the Cheshire Cat in the Duchess's house. In the movie she first sees him after she's left the house. Later when the Cat appears in the sky at The Queen of Hearts's croquet ground, Alice tells everyone that she thinks the Cat belongs to the Duchess. But Alice didn't see the cat at the Duchess's house, so how would she know?
When Alice starts growing at the Queen's court, she protests that she hasn't eaten a piece of mushroom or drunk anything. The problem is that in the movie's scene with the Caterpillar, Alice didn't learn what it was that would make her shorter or larger and just walked off without any mushroom after the caterpillar vanished.
The Day of the Triffids (1981): This 1980s adaptation has the mysterious "comet debris" that caused mass blindness and a mysterious and deadly disease that almost wipes out the survivors. In the original book, it was attributed to malfunctioning KillSats, which would have been quite plausible in the early 1950s, but the Outer Space Treaty banned the placing of weapons of mass-destruction in orbit even if anyone had wanted to do so.note Turns out that once you can put a satellite in orbit, it's only marginally more difficult and expensive to shoot one down. But when the BBC adapted the show in 1981, they decided to do a straight Setting Update, without changing this plot element. They get away with it because in both versions the viewpoint character is only speculating from the point of view of a somewhat informed layman, and what actually happened is left ambiguous.
In Elementary, Mycroft Holmes's restaurant chain is called Diogenes, as a Mythology Gag to the literary Mycroft's Smoky Gentlemen's Club. Except that while it makes sense for a club for "the most unclubbable men in London" to be named after a famously anti-social philosopher, it's not clear why an up-market restaurant chain would take the name of someone who despised luxury to the extent of living in a barrel and not, say, Epicurus.
The Flash (2014) has a tendency to give typically villains different motivations for their actions:
Captain Cold/Leonard Snart in the comics was a Noble Demon at his worst who at one point retired after the death of Barry Allen and actually befriended his successor, Wally West, but in the show he was a colder and more calculating figure who willingly killed and endangered civilians just to antagonize Flash. Despite this, in the show, Barry regularly treated him as a Noble Demon, trusting him to help the team when they needed him and encouraged a HeelFace Turn, even though Snart in the show never showed any indication he wasn't an evil bastard and betrayed Barry whenever he was trusted. He does eventually go through a HeelFace Turn when he's spun-off into Legends of Tomorrow, but that's long after they've established him as a selfish dick.
Similarly, Pied Piper also went through a HeelFace Turn in the comics and became friends with Wally West, but he was never a particularly dangerous villain to begin with and, through retcons, his motivation for his crimes were simply to rebell against his upper class upbringing and later to help the homeless. The show instead depicted him as one of the most dangerous and cruelest villains who nearly killed Barry in a slow and very painful way, and explained his later HeelFace Turn as the result of an Enemy Mine situation created by Barry changing the timeline that somehow gave him a complete personality inversion.
Caitlin Snow's transformation into Killer Frost is probably one of the most egregious cases. In the comics, when she became Killer Frost she was cursed with 'heat vampirism' that forced her to lethally drain body heat from other creatures until to sustain herself, and she had to kill just to survive. In the show, this isn't the case; initially she just really wants to be normal and was willing to attack and mutilate her own friends to do it, with the show acting that With Great Power Comes Great Insanity, something that has never been the casenote though other characters that season demonstrate this issue, its explicitly the result of Savitar/Alchemy mentally attacking them and giving them the memories of their Flashpoint selves; Caitlin, however, got her powers completely unrelated to this.
Mystery Science Theater 3000: This show had on-and-off trouble, due to the nature of its format. They had to trim out questionable content and pare down the films they riffed so that, in combination with the host segments, the show would only fill roughly 90 minutes of run time (in a two-hour time slot). The show's staff stressed that they tried not to artificially add to a film's poor quality with their edits, but it occasionally happens.
Angels Revenge: The deletion of Neville Brand's character causes a number of plot holes to crop up — namely, why the female officer is part of the group, why the police never appear involved, and what did the girls do with all the cocaine they snagged at the beach.
Mitchell: This catastrophic Joe Don Baker vehicle was 97 minutes long, but was cut down to 70-75 minutes. One of the things cut out was the death of John Saxon's character Mr. Deaney, one of the film's primary antagonists. Despite what some MSTies have mistakenly assumed, though, Best Brains was not responsible for this one; the scene was already trimmed from the Lorimar TV print of the film (Lorimar inherited the film when they acquired Allied Artists in the early 80s) they chose for riffing (explaining why they joked about Saxon's absence, as they don't pick on a movie for cuts they themselves made to it).
Sidehackers: One of the scene that had to cut out due to content involved the hero's girlfriend being brutally gang rapedand killed by the antagonist and his lackeys. In order to explain why the main heroine suddenly disappears halfway through the film, one of the bots makes the following remark:
Crow: "For those of you following at home, Rita is dead."
Out of this World (1962): "Little Lost Robot": In the original story, Dr Calvin interviews the robots individually before the second experiment, and they're left unobserved while waiting. In this adaptation, the conditions of the experiment are announced to the whole group at once and the group doesn't leave human sight until after the experiment. Yet the missing robot managed to talk the others around into not trying to save the human without any of the other characters noticing it.
The Pillars of the Earth: The Age Lift done to Richard in the miniseries adaptation causes a few problems. In the book, he's only a child and dependent on his older sister Aliena when they're orphaned and lose their home, which causes them a few problems due to the misogynistic 12th century society they're thrown into, like a wool trader who refuses to do business with her. In the series Richard seems to be the same age as her, making one wonder why he doesn't step in during situations like this. Then again, Richard doing something actually useful would be a huge Out-of-Character Moment compared to his portrayal in the books.
Power Rangers are based on Super Sentai footage, made by cutting elements of the source they either don't need, don't fit the story/setting at hand, or the American censors don't like, then adding in new footage for the "civilian" scenes. As a result, artifacts often show up out of nowhere (such as the Rangers wielding weapons they hadn't been using), and often aren't acknowledged at all.
Mighty Morphin' Power Rangers might leave some older viewers scratching their heads at the fact that the Rangers all have Zords and costume emblems based on dinosaurs, even though they got their powers and equipment from Zordon—a wise alien trapped in a time warp, who has no logical reason to be interested in extinct creatures from Earth's past. For that matter, how the hell does Zordon even know what dinosaurs look like? And if he's from another planet, why does he have a Command Center on Earth with a stasis tube to contain his consciousness? Well, in Kyoryu Sentai Zyuranger, all of those things made perfect sense. The Rangers' mentor was an immortal human wizard named Barza, the Rangers themselves were warriors from an idyllic past when humans and dinosaurs lived in perfect harmony, and their vehicles were gifts from a race of godlike beings who took the forms of animals. The American redub replaced Barza with Zordon and cut out the prehistoric backstory, but forgot to explain why the Rangers and their mentor were obsessed with dinosaurs.
Due to a veryTroubled Production, the show was basically in a state of behind the scenes chaos, so the Rangers suddenly have the Quasar Launchers in the middle of a battle, and they know how to make the Galactabeasts transform into their Galactazords with their Transdaggers without any warning.
"The Lost Galactabeasts Part 2": The Rangers learn the Galactabeasts won't attack the Brainwashed and Crazy Stratoforce and Centaurus Megazords because they are the missing Phoenix and Rhino Galactabeasts and the other Galactabeasts won't attack family. Yet the Torozord, who is unrelated to the Galactabeasts, refuses to fight too. That's because it is related to them in Gingaman, where it is classified as a "Heavy Starbeast."
Power Rangers Lightspeed Rescue: In "Sorcerer of the Sands", The Gatekeeper summons the spirits of previously defeated monsters against the Rangers. The problem is that, among the fourteen "fallen" monsters, five of them never faced the Rangers before, and two of them (Treevil and Arachnor) face them in later episodes. This is due to adapting the Sentai episodes Out of Order.
Probably the biggest is that Jayden and Lauren being siblings messes up the twist at the end quite a bit. In Samurai Sentai Shinkenger, Takeru is a Body Double for Kaoru and wasn't a real Shiba, thus his reasons for not wanting the other Shinkengers to fight with him is based on his feelings that they shouldn't risk their lives over a lie. The omission of a direct counterpart to Tanba also cuts out much of the tension between Kaoru/Lauren and the other Shinkengers/Samurai Rangers, so their rejection is very forced by comparison.
The much-maligned decision by Mentor Ji to take Antonio's morpher away. In Samurai Sentai Shinkenger, Jii does it because Genta is an even bigger doofusnote (Genta showed up at the Shiba household looking like a ridiculous Samurai caricature and generally wasn't taking things seriously despite insistence's to the contrary.) than Antonio is, and the Sushi Changer was at least partially created using the power of both the Octopus Origami and a Hidden Disk that Takeru had given him, so Jii at least is taking back something that rightfully belongs to the Shiba household because of its origin. The omission of the tinier details causes the scene to take on a very different tone than the original, making Mentor Ji out to be an Elitist Jerkass rather than well-intentioned but harsh.
One episode has the Blue Ranger losing to a sword-wielding Monster of the Week, suffering a major hit to his pride, and undergoing Training from Hell to defeat the monster. This makes perfect sense in Kaizoku Sentai Gokaiger, since their Blue Ranger is a swordsman with a lot of pride in his skill, but since Megaforce's Blue is a Hollywood Nerd, he ended up adopting Gokai Blue's personality for the duration of that episode just to make the plot work, then reverting back to normal for the rest of the series.
In "In the Driver's Seat," the rangers go to Corinth. The problem with this is that they heavily reuse the stock footage from the Kaizoku Sentai GokaigerGo-Onger tribute, thus part of Corinth becomes a raceway for no reason and the Turbo Falcon Zord had no other reason for what it was doing than just because. In Gokaiger, it was rebelling against its parents, then stopped when it became a pirate with the team.
On a minor note, Noah gets singled out by Argus for no reason. In Gokaiger, Argus' counterpart, Barizorg, is a cyber converted version of Joe's old mentor, Sid, and thus Joe is on a personal vendetta to free Sid's soul from being trapped inside Barizorg, since his skills are being used by the wrong people. Noah fought Argus because Argus had no one else he wanted to fight, I guess.
Promoting Goseiger'sDisc-One Final Boss Mons Drake into Megaforce'sBig Bad Admiral Malkor was a good case of Adaptation Distillation. But when the Rangers face him in The Human Condition, they neglect to make use of the Ultra Mode or Gosei Ultimate, both of which would have been handy against Malkor. Their Sentai counterparts were introduced after Malkor's tenure as Big Bad, but unlike Robo Knight's subplot, there's no reason for their absence.
The show also adapts out Datas, yet includes the Ultra Gosei Great Megazord that he made part of. So there's no explanation for the Megazord's backpack that appears when the combination is formed.
"The Miserable Mill" story is changed so that the Baudelaires arrive at the titular mill after running away and are taken in as illegal employees by 'Sir' (the owner), rather than being assigned to him by Mr. Poe as they were in the book. This was probably done for pragmatic reasons, as it is hard to believe that even someone as stupid and incompetent as Poe could think assigning orphans to work at a lumber mill would be acceptable, but it does make Count Olaf's Evil Plan rather pointless in the TV show. Olaf, disguised as "Shirley T. Sinoit-Pécer" tries to convince Sir to pass the children into his care by hypnotizing Klaus and making him cause an accident. As Sir has no guardianship over them in the show, he cannot legally sign them over to Olaf, and if Olaf merely wanted to kidnap them he didn't need Sir's permission to do that.
The VFD subplot being integrated into the show much earlier than it was in the books has also caused some issues. For example, in "The Reptile Room", Uncle Monty mistakenly believes "Stephano" is a spy from the Herpetological Society rather than Count Olaf in disguise. This made some sense in the books, where he had no real reason to suspect otherwise (beyond the children trying to warn him, but Not Now, Kiddo is a staple of this series) but not in the show when he's receiving secret messages from the VFD about the children being in danger.
"The Hostile Hospital": Show viewers might be scratching their heads at how Olaf could have possibly believed Klaus would ever go through with sawing off Violet's head. In the books, this happened because Klaus had taken a disguise intended for the White-Faced Women (who unbeknownst to Olaf hadn't yet arrived at the hospital). Olaf, fooled by Klaus' Paper-Thin Disguise, believed he was giving this order to one of his minions. In the show however, Klaus' disguise is a character of his own creation, and Olaf sees through it, leading to the awkward scenario in which Olaf apparently believes he can make Klaus murder his sister through peer pressure.
Supergirl: In the comics, Hank Henshaw is a metahuman with the ability to posses cybernetic bodies, his favorite being a partially-roboticized clone body of Superman, and has a personal grudge against Kal-El for him failing to save his friends. After Superman's death at the hands of Doomsday, Cyborg Superman was one of many figures who attempted to imitate or replace Metropolis's hero. Thus, his common moniker of Cyborg Superman is both obvious, a by-product of debuting alongside Steel, Superboy, Man of Tomorrow, etc, and a way of mocking his nemesis. In this series, though, Henshaw is just an "ordinary" cyborg (injured fighting the Martian Manhunter, saved from death by cybernetic implants) with a hatred of all aliens, yet he still names himself Cyborg Superman, even though he in no way resembles Superman (besides both having the common powers of super strength and durability), and should probably hate being associated with an alien (who he otherwise has little connection to.)
The Twilight Zone (1959): In "To Serve Man", the Kanamit ambassador simply leaves the book To Serve Man behind in the United Nations chamber which allows the translator Patty to determine that it's a cookbook. In the short story by Damon Knight, the equivalent character Gregori stole the book from the Kanamits and translated its first paragraph using a limited English-Kanamit dictionary.
In the comics, Woodbury was not well equipped to handle the Zombie Apocalypse and the Governor desired to move his people to the much safer prison. The TV series reversed this, making Woodbury a sanctuary and the prison less secure. This makes the Governor's vendetta against Rick's group seem rather pointless, especially given that he was fairly reasonable in his first encounter with Michonne and Andrea. He did eventually get a more plausible reason for his hatred -Revenge on Michonne for stabbing him in the eye and killing his zombified daughter- but this was only after the conflict between their groups was well underway, and it's also made clear that even if Rick handed Michonne over to him as a peace offering, he'd destroy the prison anyway For the Evulz.
Season 4 has attempted to fix this; after the first assault on the prison fails the Governor kills most of his followers and burns down Woodbury in a rage. However, after he meets Lilly Chambler and her family and bonds with them, he once again begins seeking a safer home, and with Woodbury gone he's set his sights on the prison.
The initially disproportionate personal vendetta goes for Michonne too. In both versions of the story, Michonne waits, sword ready, in the Governor's quarters with the intention of settling a personal vendetta alone and where she could take her time with him. In the TV series this seems a bit unwarranted for a man that she knows as an affable leader she herself does not trust, who may or may not have been behind Merle's orders to follow her unsuccessfully and coerce strangers back to Woodbury. In the comics, Michonne's personal vendetta stems from the Governor having restrained and repeatedly raped her, and tortured and maimed her companions. While her destruction of the Governor's eye was not done through torture in the show, it was clearly along the lines of her intentions when she waited for him in his room, despite her not having nearly as much cause for such brutality as her comics counterpart.
Cackles Academy has a fair share of teachers that aren't seen and don't come into the story that much but the TV series shows that there are only four teachers at the school - Miss Cackle, Miss Hardbroom, Miss Bat and Miss Drill - yet in the second season a Miss Gimlett is mentioned as being the Year Head for the 2nd year girls but has moved away over the summer. Miss Gimlett was never mentioned or referred to before that episode and apparently never used the staff room. In the books we didn't know what Miss Gimlett taught since the only lessons the girls were ever shown having were potions and chanting but the TV show has Miss Cackle teaching spells and no other subjects, apart from PE so that begs the question what did this elusive Miss Gimlett teach before she left?
The second season follows the third book's plot of having Mildred and Ethel banned from the Halloween celebrations after what happened last year. When the Grand Wizard sees Mildred he says straight from the book "are you not the girl who ruined the Halloween celebrations last year!" which creates a Plot Hole. In the previous season, the episode "Sweet Talking Guys" added an original plot where the Grand Wizard visits the school with some apprentice wizards and ends up impressed by Mildred during a public speaking contest. So why would he have a problem with her being at the Halloween celebrations? Especially when he doesn't reference them at all in "Sweet Talking Guys".
Griselda Blackwood's only appearance in the books was Mildred tying her up and going to the Halloween celebrations in her place. In the TV series however, Griselda is expanded into one of Mildred's friends so keeping this intact would have created a Plot Hole. So this role is given to Drucilla instead.
The Halloween Episode keeps the book's plot point of having Miss Cackle and Miss Hardbroom not believing Mildred's story about the wicked witches' attempted invasion. They only start to believe her when Mildred mentions a woman that looks like Miss Cackle - and the latter reveals she has a twin sister. This works in the book because Mildred had turned the witches into snails and thus couldn't prove herself. But in the TV show, she just shrinks them - so you have to wonder why she doesn't open the box immediately so that the two believe her. Additionally Miss Drill has been involved in the TV series, rescuing Mildred from the woods. So the other teachers should have no reason not to believe Mildred with a member of staff vouching for her. What's more is that the witches got inside the school in the TV show and Miss Cackle got turned into a frog.
Similar to the Miss Gimlett example above, the Two-Teacher School element creates minor plot holes in various episodes. With Miss Cackle, Hardbroom, Bat and Drill as the only teachers - there are plenty of instances of one teacher taking Mildred's class, and the other three wandering freely around the school. So who is taking the classes for the other years?
Inverted in one case where the book had a Plot Hole that the TV series fixed. In the first book Ethel is turned into a pig by Mildred but can still speak and so rats her out to Miss Hardbroom. The Plot Hole comes in the third book when Ethel turns Mildred into a frog and Mildred can't speak to humans. In the TV series Ethel can't speak at all when she is turned into a pig, fixing the plot hole.