Anti-Climax: The finale of the first book-Wayne and the Kingdom Keepers gather together in Cinderella Castle to see the effects of Walt Disney's first pen, which is supposed to be very important and powerful, for themselves. Wayne places it on a blueprint of the Magic Kingdom, the drawing lights up as does the whole park, a multitude of fireworks go off in the sky, and... that's it. That's all that happens. The fireworks are reported as something done for a private celebration the next morning and Wayne sends the Kingdom Keepers home. Oh, the rides fix themselves too, but that's barely mentioned.
Critical Research Failure/Dan Browned: Ridley Pearson has gone on record stating how much research he has done on how the park and rides operate...this apparently does not extend to the characters themselves, however. Depending on the kind of Disney fan you're dealing with, they're either going to see liberties that Pearson took as Acceptable Breaks from Reality or as entirely unfeasible.
Most Disney fans that don't like the books make the argument that Pearson hasn't done research into the spirit of the park itself, including the fact that Walt Disney didn't even want to use holograms in any of the rides or the park itself after being approached by a company that created them, and Imagineers have continued to stay away from using them ever since. So technically the DHIs should not even exist! However, Disney Research, a R&D division of Disney that develops technology advancements that could be used by other divisions of the company later on, has developed means for people to touch virtual objects, including holograms. Disney parks have also utilized special effects often confused for holograms, the most well known being the Pepper's Ghost illusion, used in attractions like the Haunted Mansion and the Tower of Terror.
Plus, the park is NEVER completely abandoned after it's closed, not even by characters come to life. There are cleanup crews, Cast Members double-checking rides to make sure they are working and safe, and more. Plus, if there were characters running around and chasing the DHIs, wouldn't security have noticed by now?
Speaking of which, there are a ton of characters that walk around where they're not supposed to be, like the Fantasia Brooms in the Voyage of the Little Mermaid show and the Country Bears in Mickey's Philharmagic. Not to mention Maleficent and Finn dressed as Aladdin fighting in Tomorrowland IN BROAD DAYLIGHT WITH A WHOLE CROWD OF TOURISTS WATCHING. A troper that worked as a former Character Attendant Cast Member noted that it would never go over as smoothly as it did in those books. There's always a Coordinator or Manager watching the action somewhere and ready to report to the higher-ups in any department. This kind of action qualifies for instant termination for whoever's in those costumes. Even if it's technically the characters themselves, it's strange that, beyond Rule of Cool, why nobody mentions how odd it is that it happens in the first place.
Also, the preview for the seventh book says there were six weasels with Judge Doom. There's only five in the movie. Either a new weasel has joined the Toon Patrol, or this is a very glaring version of this trope.
Let's not forget the errors in attraction names. "Fantasmic!" is repeatedly referred to as "Fantasmics" and Buzz Lightyear's Space Ranger Spin is referred to as Buzz Lightyear's Astro Blasters, which is the Disneyland version of the ride.
Overlapping with Spell My Name with an "S", Sabor is always called "the Sabor," no mention of her gender is brought up, the pronouns used are "it, its," and in a nod to the original Literature/Tarzan , is called a lioness rather than a leopard.
Fridge Brilliance kicks in when you realize that 1) Sabor is a Living Statue, making "the Sabor" another way of saying "the statue", and 2) the characters are more focused on being eaten than getting her gender right.
Darkness-Induced Audience Apathy: By the sixth book some fans have stopped reading because they feel it's gotten a little TOO dark, even by Disney standards. A blood sacrifice resulting in the death of a minor character by his best friend will do it.
Lost Aesop: "The Stonecutter's Quill" story in the first book. Perhaps it will enlighten our heroes by saying how thankful we should be of where we are now and of the advantages we have by being ourselves...but instead it's all about power...and it's never mentioned again anywhere or resonates with anything in the rest of the book.
Marty Stu: Finn, oh FINN. He instantly has the answers to everything, he's automatically the unquestioned leader of the group, and most of the girls in the books want him. Plus, he never changes, grows as a character or learns anything.
However, Maybeck does mention that he has a severe hero complex in Book 5. He also seems confused and even irritated by the fact that he keeps on getting randomly checked out, hit on and kissed by most of the girls he meets. Plus, he cares WAAAAAAAAAAAY too much about Dillard sometimes, going as far to swear at Philby and constantly arguing that his friend's life is more important. So yeah, he has some flaws-just not obvious at the start.
New Powers as the Plot Demands: By the fifth and sixth book, Finn starts having visions of the future for no reason and gains immense strength. He also gains a strange connection with Maleficent.
Rouge Angles of Satin: The later books have shockingly become riddled with misspellings. Where did the editors go?
Said Bookism: Just TRY to keep track of everytime another word is used where "said" would have been just as appropriate, if not more so.
They Wasted a Perfectly Good Plot: An adventure in the Magic Kingdom and the other Disney Parks after dark with the characters coming to life and fighting Disney villains? Sounds awesome! Until you get to the bland characters, too much focus on the technical aspects, poor characterizations of characters we already know and love...how long until Jon Favreau's Magic Kingdom movie come out?
Time Marches On: The first Kingdom Keepers book dedicates a significant portion to the five friends interacting in Virtual Magic Kingdom...which was shut down shortly some time after the book was published. Plus, every time there's a significant change in the parks, like Toontown being razed for the New Fantasyland Expansion, they have to find a way to work it into the books, mostly because it was mentioned in the story before the major change.
Wangst: Depending on your level of tolerance (and how close you are to the target age of the series), you might find Finn's concerns of his normal life (bullies, high school, love triangles, disapproving parents...) on top of fighting Disney villains to either be par for the course or utterly unbearable.
What Happened to the Mouse?: They keep mentioning and hinting towards Finn' sister, but she never makes an appearance or does anything important. Why is she even mentioned?
The Woobie: Dillard. The poor guy's been totally abandoned by his supposed best friend and he gets killed in the sixth book all because he wanted to be a DHI.