- 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.
- All Animation Is Disney: Like most of Don Bluth's work, this mistake has been made, but those who make it are generally a minority. If anything, it's most famous for being one of the best non-Disney animated features ever.
- Animation Age Ghetto: On-screen violence, death, and other trauma, as well as a casual "damn" thrown in to Avoid the Dreaded G Rating... which it still got. The film is darker in comparison to some of the tamer live-action PG-rated films of its time, such as Annie (1982) and E.T. the Extra-Terrestrial.note
- Awesome Music: It really says something about how amazing the musical score is when Jerry Goldsmith himself stated this was one of his personal favorites.
- The song "Flying Dreams".
It's even cooler when you realize that it's one of the few songs Paul Williams has recorded since he stopped releasing albums in the early 80s. - On the Italian version flirts with Alternative Foreign Theme Song by using Sally Stevens' versionover the closing credits instead of Williams'.
- To which you could add the opening credits, closing credits, Mrs. Brisby & Jeremy's flight to meet the owl, the rescue of the Brisby house... well, the entire score...
- The song "Flying Dreams".
- Base-Breaking Character: Viewers either find Jeremy one of Dom De Luise's most charming and entertaining roles, or they think his comedic antics are out of place with the film's otherwise dark tone.
- Common Knowledge: Because of a passing remark that Mr. Ages makes early on about Timothy having been bitten by a spider, fans sometimes assume that Timothy's pneumonia was caused by that spider bite. Not exactly. The original book gives a full explanation: Timothy was bitten by a spider as a baby. Thanks to medicine from Mr. Ages, he recovered, but was always Delicate and Sickly from then on, leading indirectly to his pneumonia several years later.
- Complete Monster: Jenner, in contrast to his noble brethren amongst the rats of NIMH, desires nothing but power. When 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, while the Brisby house is sinking in mud with Jenner not caring about the impending deaths of the kids trapped inside. When he sees Nicodemus bequeathed it to her, Jenner attempts to murder Mrs. Brisby for a special stone. Jenner, like all the rats, owes his very life to Mrs. Brisby's deceased husband and the father of her kids, but displays zero remorse or gratitude to Jonathan's memory. After his henchman Sullivan finally has enough with Jenner's lunacy, Jenner fatally wounds him and attempts to kill his rival Justin, declaring his only philosophy in life: Take what you can when you can.
- Cult Classic: Regarded by fans as one of Don Bluth's best works for its deep and complex story and three dimensional characters.
- Designated Monkey: Jeremy. Even regarding how much trouble his clumsiness and quirkiness causes, he's so well-meaning and innocent that it's easy to feel sorry for him, especially since most of the time he is being punished by the protagonists he's trying to help (such as Mrs Brisby's kids he was so convinced would adore him).
- Ensemble Dark Horse:
- The Great Owl is in one scene, and is probably the most well remembered part of the movie.
- Jenner has very limited screen time or characterization, and yet is still a memorable villain thanks to his menacing voice, charisma, and being genuinely scary.
- Jeremy has little prominence and very limited screen time, but nevertheless, he has a large following and fans of him, due to his clumsy and funny personality.
- Nicodemus due to Derek Jacobi's terrific performance totally selling him as a wise, mystical prophet.
- Fan Nickname: Elizabeth, as Mrs. Brisby's never-revealed first name, in tribute to her voice actress Elizabeth Hartman (who committed suicide). Some even go so far as to call her "Elizabeth Hartman Brisby".
- Fanon: The Wiki (found here) is one half actual film-based info, and one half Worldbuilding Fan Wank that explains all the plotholes in the film through an exploration of the rules of magic and the Rats of NIMH's society.
- Fan-Preferred Couple: Justin and Mrs. Brisby. There's obviously some attraction going on there, but their species difference and the fact that Mrs. Brisby is very recently widowed makes this something of a hot-button subject. Here's what the actual script has to say about their introduction:[Justin] notices [Mrs. Brisby]. She has already noticed quite a few things about him.
- First Installment Wins: Although Don Bluth did plenty of other quality films after this one, many people still agree that this is his most consistently good film. Additionally, the sequel The Secret of NIMH 2: Timmy to the Rescue is seen as vastly inferior to the first film.
- Girl-Show Ghetto: The title was changed from the source material's 'Mrs Frisby & the Rats of NIMH' to avoid alienating viewers who might think it was a movie 'for girls'. And in the 2000s, when this trope really became rampant, DVD sets that featured the sequel had Timothy front and centre on the cover - some of them not even featuring Mrs Brisby at all.
- Harsher in Hindsight:
- 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.
- 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. In the original novel, when Mrs. Frisby is taken to the library, she meets a younger rat, and the two have a conversation before she gets called to see Nicodemus.
- Hilarious in Hindsight:
- 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.
- This wouldn't be the last time Derek Jacobi would play an elderly wise person with a small medallion-sized MacGuffin. He later did so with his role as Professor Yana in Doctor Who.
- Disney was first approached about adapting the book. They turned it down saying they already had Mickey Mouse as a mascot, and likewise had already done a "mouse movie" in The Rescuers. Since The Secret of NIMH's release, Disney would end up doing both The Great Mouse Detective and The Rescuers Down Under.
- Hype Backlash: An example of an otherwise underground work being pushed on the general public by its small audience. A great deal of fans, most notably The Nostalgia Critic, have frequently gone on about how it's one of the greatest animated films ever. The result was that some newcomers were significantly disappointed when they felt it didn't meet the incredibly high expectations its fans had given them.
- Love to Hate: Jenner is the only character in the movie who could be considered evil, and is loved for it.
- Moral Event Horizon: Jenner crosses this after cutting the rope and causing the brick to crush Nicodemus.
- One-Scene Wonder:
- John Carradine as the Owl. The whole scene on both a technical and emotional level could be considered Bluth's Moment of Awesome.
- The rat Brutus has only one scene but he's also memorable.
- Jenner only has about six minutes of screen time but he's so despicable and menacing that he steals every second of it.
- Padding: After flying Mrs Brisby to the Great Owl, most of Jeremy's appearances are irrelevant to the plot.
- Retroactive Recognition: Wil Wheaton and Shannen Doherty both got very early roles as child actors in this movie, and this would mark the first of a long line of roles Dom De Luise would play for Don Bluth.
- 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 Effect Failure: Impressively animated this film and its special effects work is, the scenes of the tractor and its plow in the film are obvious live action footage rotoscoped and tinted brown on the cels, which comes off as egregious when compared to the rest of the film. Even Don Bluth admitted he didn't like how the effect looked in his book "The Art of Storyboard". note
- 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. Done by a staff of three effects animators, no less!
- What Do You Mean, It's for Kids?: Subverted. It's for families, and not necessarily ones with very young children. Bluth wanted it to appeal to a broad audience, which explains a lot of the scary imagery and the one casual "damn!" thrown in.
- The Woobie:
- Mrs. Brisby definitely goes through a lot in the movie, especially since she deals with the fact that her son is critically ill and she's a timid little mouse who must go through all sorts of dangers to save her family.
- Jeremy is a hapless Butt-Monkey throughout the film, as he is a compassionate and friendly crow and does have good intentions, but makes things worse for everyone which makes everyone think low of him.
- Timothy probably stands out the most. He is in a medical condition and can't get out of bed and Mrs. Brisby goes through hell trying to save him.
- Nicodemus, he is a wise ruler, but he gets killed by Jenner in the end.
- Sullivan is forced to work with Jenner, even though he is against his idea of killing Nicodemus and threatens his life if he refuses, and when he betrays Jenner by handing Justin his sword, he gets slashed in the ribs by Jenner and dies, but not before throwing a dagger at him as soon as he's about to kill Justin.
