Big-Lipped Alligator Moment: The two oddly-dressed wannabe rappers performing their rhymes for Jacob while showing him around the island. In addition to being incredibly out of place on Cairnholm, they have very little to do with the plot.
A few of the pictures early in the first book, of peculiar children who never appear or are mentioned again.
Base-Breaking Character: Noor in the new trilogy no thanks to the fact she replaces Emma as Jacob's Love Interest and ends up becoming arguably the most important new character due to being part of the prophecy to emancipate peculiardom. While many fans believe she has a very cool peculiarity, opinions of her still ended up souring once she and Jacob became an Official Couple in The Conference of the Birds, not helped by the fact Jacob treats her as if she's been the one giving him his strength this whole time and not Emma. Reception to her character is so divided that she is regarded as the character who either makes or breaks the new trilogy for fans of the series.
Bizarro Episode: The chapter with Sam and Esme, who never reappear again.
Complete Monster: Caul is Miss Peregrine's older brother who was envious of her status as a ymbryne. Seeking power, Caul created a splinter group that sought to subjugate normal humanity. After an attempt at immortality went awry, Caul and his followers were turned into the monstrous hollowgasts that hunted peculiars down to eat them, before becoming wights. Caul raided dozens of loops to abduct everyone inside—including the children—to either feed them to hollows or to steal their souls. Caul found the fabled Library of Souls so he could absorb the souls in there to become a god and conquer the world. Despite his cheerful demeanor, Caul was nothing more than a power-hungry megalomaniac.
Delusion Conclusion: There are some who believe (or just choose to believe) that the whole thing is in Jacob's head as some sort of coping mechanism for his grandfather's death.
Genius Bonus: Bentham and his Panloopticon, a nexus for other loops, are named after philosopher Jeremy Bentham and his proposition of the panopticon, a hypothetical prison that makes people behave because they believe they are always watched without needing to actually have watchmen active. This is actually mentioned in Miss Peregrine's Museum of Wonders.
Paranoia Fuel: Wights can look like anyone and the only way you'll know is by looking at their eyes. And even that doesn't work sometimes. And not even most peculiars can even see the hollowgasts that want to eat their souls...
Hollow City shows that wights have infiltrated the police force and the army. You can't trust anybody.
Jacob’s parents, Frank and Maryanne, are not shown to have any Hidden Depths. It’s never confirmed whether Frank really was jealous of Abe’s relationship with Jacob (as Jacob suspects in the first book) and we never see him move past his inability to give up on his interests or pet projects. It’s also never explained whether Maryanne has any real enjoyment in throwing parties and showing off her home or if she feels unfulfilled doing those things.
Aunt Susie is one of the few relatives that Jacob is close to, but she doesn’t have much to do with the events of the books nor does she ever find out about peculiar doom and the role Jacob has played in it.
There are next to no details about the lives of Miss Peregrine's wards led before they came into her care. One character in the first book tells Jacob that supposedly most of them "Didn't speak the Queen's English, or any English." Whether they came from different countries originally is never explored. With the exception of Emma, who gets her family life explored in more detail, everything that we know about the other peculiars, such as Enoch's parents being undertakers and Olive's parents abandoning her at birth are glossed over on one page.
We don't know what peculiarities Miss Peregrine's brother, Myron, has.
When Miss Peregrine and the peculiars show up at Jacob's home and his parents see that he's been telling the truth and freak out, both Miss Peregrine and Emma are optimistic that they'll be accepting of peculiardom. Unfortunately the third book ends without exploring that. There's not even an epilogue that shows how Emma and the other peculiars adapt to 21st-century Florida. However, this does become a plot point in A Map of Days.
The Woobie: All of the peculiar children count, considering they have been isolated from the entire world, first by their abilities and then by the "Groundhog Day" Loop. Some of them were abused by families who couldn't understand what they were (ex. Emma). There's also Radi in Hollow City, a boy who is slowly turning invisible, and who is terrified of vanishing completely and one day getting separated from his family because they can't see him. Talking to Millard helps him come to terms with it.
The Film:
Complete Monster: Mr. Barron is a shapeshifting Peculiar who strives for immortality. Once a Peculiar who was part of a splinter group who sought to live outside the loops, Barron and his minions were mutated into the monstrous Hollowgasts as a result of a failed experiment involving stealing the essence of an ymbryne. Barron, however, finds an especially vile manner of regaining his humanity: raiding loops, killing all the Peculiars within—specifically children—and devouring their eyes. Barron repeats this process with several other loops, with the ultimate goal to find the loop of Ms. Peregrine and use her and several other ymbrynes to start the experiment anew. Once he does, Barron coerces Peregrine into coming with him under the threat of Jacob's life, and soon leaves all the children under her care to the mercy of the approaching Hollowgasts. Even the deaths of his closest minions don't sadden, faze, or even annoy him in the slightest.
Ensemble Dark Horse: Olive. In spite of the controversy regarding her and Emma switching powers. Her fun performance, powers, and dynamics with Enoch make her a much-loved character who inspired a lot of fan art.
Esoteric Happy Ending: Jake choosing to rejoin the Peculiar Children in 1943 is treated as an happy ending but the fact that he abandons his parents is not addressed. Worst his father last saw him disappearing after finding out there's a killer on the island. We could assume he did explain things somewhat, or Abe did, but they could at least have been name-checked.
At least the latter case is explained by Jake remaining in the 2016 loop when it collapsed, 6 months before heading to the island, so he and his father never went to the island in the first place.
Evil Is Cool: Mass-murdering villain he may be, but Barron gets some of the best lines, has a real sense of style, and also impresses with his disguises, not to mention he's played by Samuel L. Jackson.
Harsher in Hindsight: A very mild case. For those watching the film after seeing the movie Get Out (2017), the use of Flanagan and Allen's "Run Rabbit Run" - particularly in its distorted form in the opening logos - can register as much more sinister than originally intended.
Hilarious in Hindsight: Eva Green as a mentor to Asa Butterfield. He had previously played Mordred in Merlin - another child of magic, whose introduction has him being snuck out of Camelot by Morgana. Eva Green had played her in the short-lived Camelot.
Narm: The ENTIRETY of the the skeleton fight against the Hollowgasts. Not to mention the music choice which contrasts against the overall tone of the film.
Nausea Fuel: The Hollowgasts eating eyes. One scene even devotes some time to eating a whole mass of them on a plate. The worst part is that it wasn't even in the book.
The entire last act is completely different from the books and makes it impossible to continue the series with future films without even more significant changes.
Visual Effects of Awesome: There are some great effects for the various peculiarities and the hollows.
came out, many called it Tim Burton's X-Men.