Angst? What Angst?: Unlike in the book, where only the protagonist managed to keep a cool head upon first realizing that hes been turned into a mouse (Bruno had a minor freak out), both Luke and Bruno seem to take being turned into mice in stride, Luke because hes now more determined than ever to stop the witches, and Bruno because hes more concerned about how his parents will react, particularly his mother, whos terrified of mice.
Anti-Climax Boss: Despite being described as a nigh undetectable race capable of horrible deeds, yet never getting caught, it was very easily to turn all of the Witches in England into mice without the possibility of them using magic to reverse the transformation.
Somewhat justified, in that the witches of the piece mainly employ potions to destroy children. The only act of magic we actually see in the book or movie is the Grand High Witch "frying" one of her subordinates. With no sign of defensive magic, turning their own potion on them makes a degree of sense.
Ass Pull: Miss Irvine having the power to reverse the effects of the potion to help Luke and Bruno. While it's arguable that the witches would have this ability considering they are shown to use spells throughout the film and they'd possibly want a safety net in case their plan backfired on them, there's virtually no buildup to it and the fact that it comes completely out of nowhere in the final few minutes feels pretty ridiculous. Granted, this was part of a re-shot "happy ending" so it makes some sense why it's there but still.
Award Snub: The film failed to get any Academy Award nominations, especially for Anjelica Huston's role. It did receive numerous other awards, including Los Angeles Film Critics Association Awards and National Society of Film Critics Awards giving Huston the prize (in a dual nomination for The Grifters.)note In fact, The Grifters might have been the reason she didn't get an Academy Award nomination, since rules state an actor can only be nominated for one film in a category in a year.
Big-Lipped Alligator Moment: The film includes a brief bit of narration from Helga explaining that she took Luke to her home in England after the car accident. No other part of the film is narrated, making this narrative choice rather odd. While the film does open with Helga telling a story, it is immediately revealed that she is speaking to Luke.
Complete Monster: The Grand High Witch is the ruler of the child-hating witches, and the most malevolent of them all. A vicious demon with a propensity for abusing and murdering her own underlings, the Grand High Witch has spent decades teaching her followers ways to dispose of as many children as possible. Unsatisfied with her followers' progress, the Grand High Witch schemes to wipe out every child in England by utilizing a potion to transform them into mice, then watch as they are killed by their own oblivious parents and teachers. Demonstrating this on one hapless boy, the Grand High Witch follows this up by kidnapping the main character and inflicting upon him the same fate. With a cruelty unmatched by her underlings, the Grand High Witch instills terror in everyone who knows of her, friend and foe alike.
Esoteric Happy Ending: Subverted. The book seems to be coasting to a happy ending, but turns out more bittersweet. Luke and his grandmother find the main register to all the Witches in the world and intend to turn them into mice, but Luke is still a mouse, with absolutely no prospect of ever turning back into a boy. It's even mentioned that he's only going to live another nine years at the most before he dies, because he's a mouse.
The book explicitly mentions in the beginning that there is at least one variety of all-male demon out there. What normally happens to your prospects when one of your biggest competitors is removed?
Evil Is Sexy: The Grand High Witch, although averted when she's not wearing her mask.
Mr. Stringer in the film wears almost exactly the same outfit as one of Rowan Atkinson's most famous characters, Mr. Bean. The film was released about six months after the first episode of Mr. Bean aired, though was filmed before it.
Moral Event Horizon: In the film, if the plan to turn all children in England into mice wasn't horrible enough for you, the Grand High Witch pushes a baby in a carriage down a cliff to draw Luke out.
Narm: The movie has a bizarre out of character moment for Mr. Jenkins. During the dinner scene, he greets the Grand High Witch by saying "Good evening" with a smile which makes it clear that he's got butterflies in his stomach. While he was established earlier as having a crush on her, bear in mind that this is not only in the midst of the witches in various stages of mouse transformation, he's also just witnessed definitive proof of his son being a mouse, not to mention being right next to his traumatised wife who is clearly nearly catonic on witnessing the very same thing. Given that, his reaction is weird.
Nightmare Fuel: Both versions of the Grand High Witch, the book version is filled with heavily implied Fridge Horror of hiding even worse things under her dress just by the fact her face looks rotten. The movie has her being a very hideous depiction of a hag.
Any woman can be a witch, can capture you at anytime and smell you out if you try to hide.
Particularly when female teachers read the book, as Dahl includes a passage that starts something like "perhaps even your lovely teacher is a witch... she might even be smiling!" And every kid in the room suddenly starts inspecting her nostrils and the color of her teeth.