These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Secret of NIMH
The Secret of NIMH
Adaptation Displacement: Book? What is this book you speak of? The film is much more well known than the source novel. Even the poorly received sequel seems to be more famous.
This is not helped by the ebook being available only on the UK iTunes Store.
Complete Monster: Jenner is a nasty, murderous piece of work. In contrast to his noble brethren amongst the rats of NIMH, Jenner desires nothing but power. When The Hero Mrs. Brisby comes to the rats for help moving her family and house to be safe from a farmer's plow, Jenner sabotages the moving so the wise and kind leader of the rats, Nicodemus is crushed to death. When he sees Nicodemus bequeathed a special stone to Mrs. Brisby, Jenner attempts to murder her for it. What makes it even worse is Jenner, like all the rats, owes his very life to Mrs. Brisby's deceased husband and the father of her kids and displays zero remorse or gratitude to Jonathan's memory. After his henchman Sullivan finally has enough with Jenner's lunacy, Jenner slashes his throat and attempts to kill his rival Justin, declaring his only philosophy in life: take what you can when you can.
A mild case, but at some point Mr. Ages asks Justin to take Mrs. Brisby to the library (where she can wait before meeting Nicodemus). Yet it's later revealed that she only has very basic reading skills, and thus would probably not be able to enjoy the reading of a book.
Don Bluth once said in an interview that if he came back for a sequel he would make Timmy the villain and Martin the hero out to stop him. When the sequel came out, the exact opposite happened.
In one scene Mrs. Brisby jumps out of a bird cage with a string to break her fall. In real life, her voice actress Elizabeth Hartman committed suicide a few years later by jumping to her death.
Magnificent Bastard: Jenner is regarded as one of the most successful villains in film history. Since he makes the falling of Mrs. Brisby's house and Nicodemus' death look like an accident, no one suspects his cruel deed... until Justin finds out about his plans from Sullivan. Had he counted on that as well as Mrs. Brisby warning the other rats about NIMH coming to exterminate them, he would've gotten away with it.
Moral Event Horizon: Jenner crosses this after cutting the rope and causing the brick to crush Nicodemus.
Ship-to-Ship Combat: Back in the early days of the NIMH fandom, there was a good amount of battle between Justin x Brisby and Jonathan x Brisby (substitute Brisby for the Fan Nickname if desired); this was fueled by a still image of Justin and Mrs. Brisby kissing, rumored to be a shot of a scene cut from the movie; Word of God killed this notion fairly quickly, but the fandom picks at it from time to time.
Special Effects Failure: The bulk of the film has impressive animation and special effects work, but some of the scenes of the Tractor and its plow during the Moving Day sequence are obvious live action footage tinted in brown, which sticks out like a sore thumb compared to the rest of the films art.
Visual Effects of Awesome: Between the lightning sparking off Brutus's halberd, the lightshows from Nicodemus' Crystal Ball, the Mind Screw-y visuals during the NIMH flashback sequences, and the amulet coming to life at the end, the light effects are utterly dazzling.
What Do You Mean, It's for Kids?: It's hard to tell whether this is really a family movie. Graphic on-screen character death, horrifying creatures, a completely superfluous "damn", several psychologically disturbing scenes.
First is Nicodemus' prophecy. It was never mentioned in the first film and was just thrown in for the purpose of giving the film a plot. What's even more jarring is that Nicodemus may have had telekinetic abilities, was wise and had a magical viewing globe but it was never made explicit that he could tell the future. And if he could see the future, shouldn't he have seen that brick coming?
Second is Mrs. Brisby's letter to Timmy that Martin is missing. You would think that because Martin is an important character in the story that this letter should be an important plot point, but it is thrown in quite far into the movie just to explain that Martin went missing. It even looks like Timmy pulled the thing out of his ass.
Big Lipped Alligator Moment: The "Magic Mystery Show", sung by Jeremy and Cecil, accompanied by a bunch of dancing forest animals. It gets really ridiculous at points (Cecil's 'Optimouse' credit card is every bit as nonsensical as a Bat Credit Card,) and after the animals realize it's a scam and chase Jeremy and Cecil away, no one talks about it again.
Sympathetic Sue: Timmy. He is praised as a hero, before he even hits puberty or does anything worthwhile. He spends much of the movie angsting over his dead father and his supposed destiny to follow in his footsteps. He is generally reckless and inattentive, and yet he still manages to save several other characters, largely by accident. Anyone who disagrees with him is portrayed as in the wrong, and to top it off, he gets the girl after a single line of dialogue.
To give an idea, Mrs. Brisby is in the film for about a grand total of 25 seconds. No recognition is made of the amazing stuff she did towards the end of the first film, not even a "Hey, that was some cool stuff you did." The entire conflict of the movie is an extremely obvious Self-Fulfilling Prophecy that can be seen a mile away, the songs absolutely suck, and almost as if to call attention to the horrible animation, there are a few clips from the first film at the beginning, which actually serve to remind the viewer that "Hey, remember this movie? You should be watching that one again, not this one. See how much better it looks?"
As with many of the unofficial Bluth sequels, Timmy To The Rescue is popular with some younger audiences due to the Lighter and Softer setup (which was likely what was intended).
They Just Didn't Care: The original was filled with deep philosophical messages and filled with superb animation...the sequel is a glorified ripoff of almost all of the DisneyficationCliché Storm that happened with the late 90s to early 2000s animated sequels with little resemblance to the original film.
What Do You Mean, It's for Kids?: Remember all those scientists brainwashed into acting like animals and forced into cages? They were never shown freed, implying they burned alive inside the Nimh Facility.
The fanfic "Rats of Thorn Valley" spawned a Muck (NIMH Muck), which has its own continuity spanning from the end of the fic to around ten years after the movie and is still going strong.
Some fanon states that Jonathan is alive; the fic listed above explains how he could be, and it actually makes sense.
General fanon stated that the mice survived their drop in the shaft, mostly because because it was a cool plot point and was a little open to interpretation. Funnily enough, this idea was actually picked up by the sequel.