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Characters / The Secret of NIMH

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Characters from The Secret of NIMH and The Secret of NIMH 2: Timmy to the Rescue. All spoilers are unmarked. Read at your own discretion.

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    Mrs. Brisby
"I would do anything for Timothy. Anything."
Voiced by: Elizabeth Hartman (original movie), Debi Mae West (sequel)

Mrs. "Elizabeth" Brisby is the sweet and motherly main protagonist and female lead. A field mouse and the wife of the late Jonathan Brisby, she will do anything to protect her children, no matter the odds.

  • Accessory-Wearing Cartoon Animal: Her only piece of clothing is her iconic red cape.
  • Action Mom: She's an interesting example of this trope, as she is doing what she does only to protect her children ("Timothy... remember Timothy!"). It is certainly not because she enjoys adventure or action. In fact, the film clearly shows that she's scared out of her mind by the dangerous tasks she must do, but she is still courageous enough to pull through, especially when the action really gets going.
  • Adaptational Intelligence: While Ms. Frisby wasn't dumb in the original novel, the book still took strides to demonstrate that she was nowhere near as intelligent as the NIMH mice and rats. She struggled to even slightly read and she didn't understand concepts like turning on a light switch of lifting a latch to open a cage. In the movie, the only notable difference between Ms. Brisby and the NIMH subjects is that she is less book smart than they are.
  • Adaptational Name Change: Her last name in the original novel was Frisby, with an F, but the movie subtly changed it to Brisby so as to avoid association with the trademarked name of the toy Frisbee.
  • All-Loving Hero: Mrs. Brisby is nothing but kind towards everyone she meets, even people as unapproachable as Auntie Shrew and Mr. Ages. It's telling that, even though she already has to think about helping Timmy with his pneumonia, she still stops in her track to help Jeremy free himself from thread when she first meets him.
  • Badass Adorable: An humble and meek little mouse girl with adorable blue eyes, her sheer cuteness makes it even more awesome when she's able to overcome her fears and face impossible odds for the sake of her children.
  • Badass Cape: A unique Subversion, as her cape actually further establishes how unremarkable and vulnerable she may seem, with her wearing a plain red one with lots of tears that, rather than making her seem bigger or more badass, just makes her look even meeker as she almost defensively covers herself with it. At best, her cape is badass by association due to who is wearing it.
  • Badass Normal: What makes her feats even more impressive is that, unlike the rats of NIMH or her husband, who were all uplifted into geniuses in a laboratory, Mrs. Brisby is a regular field mouse who still manages to accomplish a lot with her natural wits and strong will.
  • Bespectacled Cutie: In the sequel, as one of the signs she's grown much older.
  • Beware the Nice Ones: She tries to be tolerant, but Jeremy's buffoonery becomes so aggravating that even Mrs. Brisby is getting blatantly pissed off with him as the film continues.
    Jeremy: I think I have real potential. I mean, girls go for the athletic type, don't they?
    Mrs. Brisby: Jeremy, you're stepping on my tail!
  • Be Yourself: Brisby's advice to Jeremy on how to win over "Miss Right" even with no "sparkly" is to simply show her what an "athlete" he is, as she is just as clumsy as he is.
  • Brainy Brunette: A mouse with brown fur who manages more than once in the film to get out of a pickle using her wits despite not being an Uplifted Animal like her husband or the rats.
  • Contralto of Danger: Elizabeth Hartman lends her soft voice as Mrs. Brisby in the 1st film.
  • Cowardly Lion: She has "courage of the heart," which among other things means that she does what she can to save her family despite being constantly overmatched and usually terrified. This is a movie that never forgets that its heroine is a timid prey animal.
  • Deadpan Snarker: Yes, even Mrs. Brisby manages to throw snark when Jeremy starts getting particularly bothersome.
    Jeremy: Right. When you're right, you're right, and you're right. None of the girls I meet wanna get serious.
    Mrs. Brisby: I doubt they'd survive.
  • Deconstructed Character Archetype: Mrs. Brisby is likely one of the most realistic takes on the Action Mom, Badass Normal and Badass Adorable tropes. Mrs. Brisby is first and foremost a normal field mouse and housewife, so when her duties as a mother force her to face great threats, she is completely out of her field and, instead of shedding her fears in the face of her goals and becoming a straight up badass like she would if this was a regular animated film, she is constantly panicking, with many scenes of hesitance from her to the point where she has to remind herself of Timothy just to carry on. However, this, in a way, is ZigZagged into a Reconstruction of these tropes as her blatant fear and meekness make her stand out as badass in her own way as she still manages to save the day against great odds.
  • Demoted to Extra: Infamously in the sequel, where she goes from The Hero of the first film to just an elderly side character with less than a minute of screentime.
  • Determinator: She proves downright resilient in her goal to protect her family despite her meekness.
  • Distress Ball: She's an Action Mom, but an inexperienced one, so she requires help several times. Justin, Aunt Shrew and even Jeremy save her life on separate occasions.
  • Dude, Where's My Respect?: The sequel completely ignores everything that Mrs. Brisby did in the first movie (ie the one that people actually like) in favor of giving a massive amount of praise to her late husband, Jonathan Brisby. Sure, Mrs. Brisby is arguably too modest to bring this up herself and would probably decline a statue built in her honor but the fact that nobody else in the sequel even so much as points out that Mrs. Brisby saved everyone and is at least as deserving of praise as Mr. Brisby makes the movie seem far more sexist than it should have. Oh, and the opening of the movie only refers to her as a widow.
  • Dull Eyes of Unhappiness: The one noticeable time in the film where her irises lose their glimmer is when she looks in utter horror at her house sinking in the mud with her family in it.
  • Earn Your Happy Ending: Boy howdy. She goes through a a lot of physical and emotional pain in the first film, but not only does she save her family, but her warning to the rats saves them from NIMH as well.
  • Even the Loving Hero Has Hated Ones: very, very downplayed, as she's still good friends with him, but in an entire film where she is very polite towards everyone, even people as offputting as Jenner, Jeremy is the only character that truly tests Brisby's patience, even to the point of overt irritation and at various points she sends him on pointless quests just to be polite about him having to get lost.
  • Fragile Speedster: Comes with her being a mouse, making her much smaller than most of the other characters, be they rats or birds, and she's definetely too meek for any physical confrontation, so her main physical ability is her very high speed, especially since, unlike the rats, she's still animalistic enough to go for quadrupedal dashes.
  • From Bad to Worse: Poor, poor Mrs. Brisby. For most of the first film, her primary motive is helping her young son Timothy, who was bitten by a spider and fell ill with Pneumonia, and she has to fend off by herself to save him after having lost her husband a few days earlier. Due to Jenner's sabotage of the moving of her house, she then also has to worry about her entire house sinking in the mud, with all her children in it. When it seems she has lost them before the stone comes to her aid, the look on her face is absolutely heartbreaking as she tries to break free of Justin's restraint, looking like she'd rather die with her children than leave them. Thankfully, she eventually manages to save all her family...until, in the sequel, Martin disappears as he's abducted by NIMH. It's honestly a good thing we weren't there to witness just how much this must have broken her before Timmy saved Martin years later.
  • Furry Reminder: Her movements stand out from that of any other named rodent in the film, besides Shrew, because she's the only one who, in particularly tense situations or to go faster, will ditch bipedalism and start running on all fours. It's a subtle but key indication that unlike her husband, Mr. Ages, the Rats of NIMH and even her children by half, she's not an Uplifted Animal but a simple field mouse.
  • Good Colors, Evil Colors: She's a Primary-Color Champion and a normal brown mouse wearing a plain red cape, emphasizing her endearing humilty, while her Innocent Blue Eyes make her look particularly adorable. In contrast, Jenner is a Secondary Color Nemesis and dresses very elegantly with primarily purple clothing, empashizing his utter pride while his green eyes and weirdly blueish fur help in making him look untrustworthy and menacing.
  • Good Parents: She's motherly and protective of all her children, while still scolding them when they deserve it. If facing off against predators much larger than yourself just to save your sickly son doesn't prove you're an amazing mother, very little can.
  • Half-Dressed Cartoon Animal: In the sequel, she's turned into one, ditching her cape for a full on robe, although her lower half is still bare.
  • The Hero: Her efforts to save her ill son are the main focus of the first film.
  • Hysterical Woman: Mrs. Brisby is very neurotic and timid, but given the circumstances she goes through, it's understandable she'd be scared out of her wits. When she tries to warn the Rats that NIMH is on their way to kill them, Jenner even accuses her of being hysterical.
  • Innocent Blue Eyes: Her adorable, glimmering light blue eyes should be the first sign that she's a kind soul and all of her heroism across the film as she sets off to save her son Timothy will confirm it.
  • Mama Bear: Mrs. Brisby will do anything for her children. In fact, the whole plot progressed when Timothy became ill, she became willing to do anything to save him, even if it meant visiting the Great Owl and the rats of N.I.M.H. (The National Institute of Mental Health).
  • Mayfly–December Romance: The main reason her late husband Jonathan never told her of NIMH or any of his experiences there was because he knew she'd have been heartbroken to find out she was the mayfly, as the expanded lifespan Jonathan was given from the experiments would have meant he'd have outlived her by a long shot. Of course, we know who actually ended up outliving who...
  • Never a Self-Made Woman: Mrs. Brisby would not have gotten any help for her situation if she wasn't, as they keep calling her, "Mrs. Jonathan Brisby." Though she ultimately succeeds based on her courage and inner strength, the sequel effectively demotes her to extra to focus on her son.
  • Nice Girl: Endlessly humble and kind to all around her, trying to be polite even when at the ends of her wits with Jeremy's tomfoolery.
  • Nice Mice: A textbook example, being tender, humble and caring.
  • No Full Name Given: Mrs. Brisby's first name is anyone's guess. Although she's at one point referred to as "Mrs. Jonathan Brisby" by Justin in front of the Rat Council, that was very likely just him wanting to let them know she's the wife of that Brisby and there's little to no likelihood that's her real name. The fans have simply resorted to nicknaming her Elizabeth, in honor of her later voice actress Elizabeth Hartman.
  • Odd Friendship: She is a shy, meek and brave field mouse, she is also a sweet widowed mother of four children, while Jeremy is a clumsy, immature and cowardly crow, that although very cowardly with The Great Owl, he's the only character shown directly attacking Dragon. And although the two become friends, Mrs. Brisby can be very easily irritated by Jeremy, due to his clumsiness and quirkiness. She does seem to like him when he isn't causing trouble for her, however.
  • The Power of Love: Her love for her children is what motivates Mrs. Brisby throughout the film, and gives power to the stone bequeathed to her by Nicodemus when her children are in danger in the climax.
  • Primary-Color Champion: Aside from the natural browns and pinks of her body, her main colors are the light blue of her eyes and the red of her cape. When she equips the golden necklace containing the stone, yellow is also added to her colors. In the sequel, however, secondary colors are added to the mix as her red robe has some purple lining.
  • Red Is Heroic: Her iconic red cape, which even became a Canon Immigrant in the novels. It's fitting that the stone, which allows her to turn her motherly love into powerful magic is also red.
  • Shabby Heroes, Well-Dressed Villains: The humble and pure-hearted Brisby is almost fully naked safe for a very worn out red cape, while the evil Jenner is dressed impeccably, with an actual Badass Cape to boot, which perfectly shows his pride.
  • Shrinking Violet: Mrs. Brisby is heroic, but blatantly meek.
  • Silver Fox: a case where the "Fox" part refers to her cuteness and prettiness rather than outright sex appeal, obviously. Although she's much older in the sequel, glasses and greying hair as proof, her motherly adorableness hasn't faded one bit.
  • Spanner in the Works: Originally, Jenner uses her situation to ruin Justin and Ages' project for Thorn Valley by killing Nicodemus in an "accident" in the operation to move Brisby's house, but it's her who would eventually unwittingly and utterly ruin his plan of remaining by overhearing a conversation Fitzgibbons had on the phone and warning everyone that NIMH was on its way.
  • Struggling Single Mother: After her husband Jonathan died, she's left all alone (safe for help from Shrew) in raising and taking care of her 4 children. She is clearly capable of being a mother to them even if on her own, the "struggling" part comes from the fact she also has to save her children, one bedridden with pneumonia, from the yearly plough, which, from the point of view of a mouse like her, is outright Armageddon.
  • Tertiary Sexual Characteristics: Without hearing her talk, the main reason you can tell she's a woman while her husband Jonathan is a man is she has visible eyelashes.
  • Tsundere: She's only really this to Jeremy, who manages to annoy even her into a Deadpan Snarker, but besides that, she's a Nice Girl for being motherly and kind.
  • Wide Eyes and Shrunken Irises: Played for Drama as she gets them upon seeing her house completely sink in the mud with her family inside, empashizing just how distraught she is at the sight.

"Excuse me, pardon me.."
Voiced by: Dom De Luise

Jeremy is an amateurish crow and a friend of Mrs. Brisby's.

  • Adaptational Comic Relief: He's a pretty straight-laced character in the book. In the film, he's a clumsy Butt-Monkey who suffers through all kinds of hilarious abuse.
  • Apologizes a Lot: He typically mutters, "Excuse me, pardon me." After he bumps into something or somebody.
  • Ascended Extra: He has more scenes in the film than he does in the book, as well as a more defined personality.
  • Badly Battered Babysitter: Jeremy's attempts at looking after Mrs. Brisby's children end with him being tangled up in yarn by Auntie Shrew, and interrogated by the Brisby kids who want to know where their mother is.
  • Big Damn Heroes: Flies in to save Timmy at the very end of the second film's climax.
  • Birds of a Feather: A literal example. He finally meets Ms. Right, who's just as clumsy as he is.
  • Butt-Monkey: Quite The Klutz indeed, and always finds himself at odds with the protagonists when he's just trying to help as his intentions are misunderstood by Auntie Shrew and Brisby's kids.Though, he does finally meet "Miss Right" at the end of the film, and seems to be on better terms with the main characters by the sequel.
  • Catchphrase: "Excuse me, pardon me..."
  • Clever Crows: He's not overtly so, and is more a naive bumbler, but he can be capable if he puts his head to it.
  • Comedy Duo: With Cecil the Caterpillar in the sequel. Also with Mrs Brisby to a lesser degree in the first film.
  • Cowardly Lion: He also appears to get scared rather easily as he seems to be fearful of Dragon and the Great Owl. Despite this however, he's more than willing to defend Mrs. Brisby from Dragon.
  • Crash-Into Hello: How he finally meets his "Miss Right", except she's the one that does the crashing into him.
  • Crouching Moron, Hidden Badass: Despite spending much of the movie as The Load, he is the only character who directly attacks Dragon, successfully rescuing Mrs. Brisby from it. After she is left distraught at losing Timmy's medicine in the process, Jeremy seems to just lose track of conversation when suddenly:
    Jeremy: Oh by the way, you dropped this back there.
  • Dark Is Not Evil: Darkness downplayed. Jeremy is a crow and therefore black in colouring. These are about his only dark qualities and he is not only one of the good guys but also very bumbling and awkwardly endearing.
  • Earn Your Happy Ending: In the first movie, after spending the whole film being a clumsy Butt-Monkey, he finally gets his Miss Right and they both fly off in the sky in the end.
  • Giant Flyer: Jeremy is seen as a Giant from the point of view of mice and shrews.
  • I Am Not Weasel: Aunt Shrew calls him "Black Buzzard", before she leaves and Cynthia innocently calls him "Turkey" and he clarifies that he is not a turkey and when he meets Miss Right, Cynthia thinks that "Miss Right" is another turkey.
  • Innocently Insensitive: When first meeting Mrs. Brisby, he proudly exclaims how wonderful love is and asks Brisby is she ever felt its beauty. Unwittingly to him, she had lost her husband a few days earlier.
  • Intellectual Animal : Despite the fact that Jeremy is not very smart, he has an intellect equal to that of mice.
  • Interspecies Friendship/Odd Friendship: ​The friendship between Jeremy and Mrs. Brisby, in the book The Great Owl is surprised by the friendship of the two.
  • Kindhearted Simpleton: Jeremy means well, but his denseness usually does more harm than good.
    Mrs. Brisby: If you're going to feather a nest, you've got a lot to learn about how to treat a lady.
    Jeremy: Right. When you're right, you're right, and you're right. None of the girls I meet wanna get serious.
  • The Klutz: He's quite clumsy, especially when he's tangled in string.
  • Lovable Rogue: Under Cecil's direction, he poses as the Great Owl to scam the other animals in the sequel.
  • Nice Guy: Jeremy is kind and compassionate, if completely ineffectual.
  • Pair the Dumb Ones: He finally finds his "Miss Right" when meeting a lady crow that is somehow as big of a clumsy doofus as he is, they hit it off perfectly.
  • Plot Allergy: Jeremy's allergic to cats, and he lets off a few good sneezes whenever near Dragon.
  • Red Is Heroic: He wears a red string around his neck.
  • Red String of Fate: In what may or may not be an intentional usage: when Mrs. Brisby first meets Jeremy, he is tangled in red string which he is retrieving to build a "love nest" for his future Ms. Right. The end of the film has Jeremy and his love interest flying and holding the two ends of the string.
  • Shooting Lessons From Your Parents: in the book, Jeremy mentions that his father taught him many things in life such as "what kind of a humor he's in" (when before seeing The Great Owl in the book) and the lee.
  • Thieving Magpie: A rare case: A real-life myth says that crows tend to collect shiny objects, that's probably why Jeremy was hypnotised by Brisby's stone.
  • Tenor Boy: Dom De Luise lends his high-pitched voice as Jeremy in the 1st and 2nd film of The Secret of NIMH.
  • Throw the Dog a Bone: After all the comedic abuse he suffers in the first film, he finally gets his "Miss Right". He's also on seemingly softer terms with the Brisbys and Aunt Shrew in the sequel (Timmy in particular almost never says a bad thing about him).
  • Toothy Bird: Some scenes show him with teeth.
  • Tritagonist: While he mostly serves as Filler, Jeremy appears recurrently throughout the entire film as the main arc revolves around Brisby and Justin.
  • Undying Loyalty: For someone he just met, he is surprisingly diligent to Mrs. Brisby's needs. She wishes he wasn't so much.
  • Vague Age: In the book, Jeremy is described as a young one-year-old crow (although arguably one year equals 15 crow years), but in the film, Jeremy has the voice and appearance of an adult crow, but in the Preproduction of Sketches Of characters from the film Jeremy is described in the sketches as a 16-year-old young crow.

    Timothy "Timmy" Brisby
Voiced by: Ina Fried (6 years old, original film), Andrew Ducote (10 years old, sequel), Alex Strange (13 years old, sequel), Ralph Macchio (17 years old, sequel)

Timothy "Timmy" Brisby is the 2nd youngest child of Mrs. Brisby.

  • Aesop Amnesia: He should have listened...
  • Ascended Extra: Timmy didn't get much screentime in the first movie because he was sick. The sequel upgrades him to a protagonist.
  • Big Brother Worship: Timmy looks up to Martin and always strives to be like him.
  • Blue Is Heroic: His blue t-shirt at 10 and then his blue vest at 17.
  • The Chosen One: In the sequel, he's chosen to lead the rats out of NIMH.
  • Delicate and Sickly: What moves the plot along is Timmy being ill with pneumonia and Mrs. Brisby trying to find treatment and a better place to live so he can heal properly.
  • Fatal Flaw: The sequel shows that Timmy doesn't listen to others when he needs to.
  • In-Series Nickname: Prefers to go by "Timmy".
  • Leeroy Jenkins: In the sequel, he has a bad habit of being stubborn and impulsive and doesn't think before he acts.
  • Nice Guy: Timmy is brave, kind-hearted, and well meaning.
  • Small Role, Big Impact: He doesn't even speak until the conclusion of the film, but it's his illness that drives Mrs. Brisby's desperate struggle to protect her family.
  • Spin Off Spring: The sequel focuses around him.
  • Unwitting Instigator of Doom: His arrogance in the sequel ends up putting his friends in more danger than they otherwise would've been.
  • "Well Done, Son" Guy: Timmy even has a song of him wanting to prove that he will make Johnathan proud.

    Martin Brisby
Voiced by: Wil Wheaton (original movie), Phillip Van Dyke (12 years old, sequel), Eric Idle (19 years old, evil, sequel), and Phillip Glasser (19 years old, reformed, sequel)

Martin Brisby is the strongest and the eldest son (and second-eldest child) of Mrs. Brisby.

    Teresa Brisby
Voiced by: Shannen Doherty (original movie), Jamie Cronin (sequel)

Teresa Brisby is the eldest of Mrs. Brisby's children.

  • Adaptation Dye-Job: Teresa in the original film had blue eyes like her mother, but in the sequel she possesses heterochromia which is odd as her father had brown eyes, so where she inherited her green eye is unknown.
  • Demoted to Extra: Along with Cynthia, Teresa's screentime in the sequel was dwarfed in comparison to the first film.
  • The Dutiful Daughter: The responsible and mature one of Mrs. Brisby's children. She aspires to be like her mother when she grows up.
  • Graceful Ladies Like Purple: She wears a lilac colored dress throughout the first film.
  • Nice Girl: Sweet, kind, mature, and responsible.
  • Tomboy and Girly Girl: She is a tomboy to her younger sister, Cynthia's girly girl.

    Cynthia Brisby
Voiced by: Jodi Hicks (original movie), Whitney Claire Kaufman (sequel)

Cynthia Brisby is the youngest one of Mrs. Brisby's children.

    Auntie Shrew
"Why me, that I alone should be responsible for the welfare of the entire field? It's monstrous!"
Voiced by: Hermoine Baddeley (original movie), Doris Roberts (sequel)

Auntie Shrew is the baby-sitter for Mrs. Brisby's children.

  • Ascended Extra: She becomes a babysitter for the Brisby children in the film. She is merely referred to as "the shrew" in the novel.
  • A Dog Named "Dog": A shrew named Shrew.
  • Drama Queen: She's a stereotypical gossipy dramatic put-upon old woman, yet she's quite the badass when called upon.
  • Good is Not Nice: She's both rude and haughty at the best of times, but is also amongst the most courageous characters next to Mrs. Brisby herself.
  • Gosh Dang It to Heck!: In the sequel ("Oh, to heck with him...").
  • Honorary Aunt: She's a friend of the Brisby family they call "Auntie".
  • Jerk with a Heart of Gold: While bossy and kind of obnoxious, she has good intentions, wanting only to ensure the safety of her friends and neighbors, especially the meek Mrs. Brisby. She's first introduced as a pish-posh busybody who walks around with an incredible air of self-importance, but she soon demonstrates great bravery by warning all the animals about the plow, rescuing Mrs. Brisby and stopping the tractor all on her own.
  • Large Ham: She seems to think she's in a perpetual Shakespearean play, Trrrilling Rrrs and all.
  • Meaningful Name: A twofold. Her name indicates both her species and the fact that she's a rude and haughty woman.
  • Never Mess with Granny: She leaps into Mrs. Brisby's aid to rescue her from the tractor without trepidation, and performs the below-mentioned feat of tying up Jeremy.
  • Offscreen Moment of Awesome: Hog-tying Jeremy in string when he approached the Brisby house. Granted the only danger Jeremy poses is accidental and he's about as hapless as a Great Dane puppy on rollerskates, but she didn't know that.
  • The Skeptic: Absolutely despises rats and scoffs at Jeremy and the kids' claims that they are coming to help the family move their home to safety. Subverted in the sequel, where now she completely believes in Nicodemus' words.
  • Trrrilling Rrrs: She puts a lot of emphasis on her r's.
  • Verbal Tic: Her Trrrilling Rrrs put The Demon Sisters to shame.

    Mr. Ages
"Now that is an emergency."
Voiced by: Arthur Malet

Mr. Ages is one of the two surviving mice of NIMH (the other being Jonathan Brisby) who lives in the Fitzgibbons farmland and is well-acquainted with machinery and medicine.

  • Big Ol' Eyebrows: He has very thick, bushy eyebrows.
  • Broke Your Arm Punching Out Cthulhu: Or rather: Broke Your Leg. When Mrs. Brisby meets with Mr. Ages inside of the Rosebush trying to seek an audience with Nicodemus, his left leg is now shown to be in a cast. It's revealed by Justin that this is because Mr. Ages had to go into the Farmhouse to leave a sleeping draught inside of Dragons' food dish so the other Rats could work in the open on large-scale projects without having to worry about being attacked by the cat.
  • Cool Old Guy: He's a skilled physician, well-acquainted with machinery and overall very intelligent; he's also a very noble character, despite being a bit grouchy and sulky.
  • Good is Not Nice: As with Auntie Shrew, he's an old grump who nevertheless comes through when Mrs. Brisby needs help.
  • Grumpy Old Man: He's an abrasive misanthrope, but his heart is very much in the right place. Auntie Shrew who is a grumpy old woman herself, even refers to him as "that old flim-flam".
  • Handicapped Badass: He spends much of the original film with a broken leg. That doesn't stop him from stepping into Mrs. Brisby's defense when Jenner goes Ax-Crazy.
  • Haughty "Hmph": He gives a couple of these to Mrs. Brisby when she pleads for advice on her son's condition.
  • Hidden Heart of Gold: For the most part he's a cranky, unsociable hermit, though he nevertheless assists Mrs. Brisby with every plea she makes to assist her family. Also, he's revealed to have been quite the badass himself, being the one previously tasked with drugging the cat before he injured his leg, as well as playing a part in the rats' escape alongside Jonathan Brisby.
  • Jerk with a Heart of Gold: He's haughty, gruff and not very social, but he does help Mrs. Brisby willingly.
  • Manly Tears: He mourns Nicodemus' death, and is emotional enough to weep for his fallen comrade.
  • Not Even Bothering with the Accent: Arthur Mallet's native English accent slips through a lot, even though Mr. Ages is leaning more towards American.
  • Sole Survivor: With the death of Jonathan Brisby shortly before the film, Mr. Ages is the last surviving Mouse of NIMH.
  • Took a Level in Kindness: He is far less gruff in the sequel, having more of a grandfatherly relationship with Timmy.

Voiced by: Frank Welker
The corpulent, beastly cat of the Fitzgibbon family.
  • Animals Not to Scale: He's a little too big for even a good-sized housecat, being closer in size to an almost medium-sized dog.
  • Catlike Dragons: An inversion of sorts - he's a regular house cat named Dragon who is seen as a draconic monster by the smaller animals.
  • Cats Are Mean: The cat in question is named Dragon. What is very interesting about this is that, in the scene where Mrs. Fitzgibbon is hanging out the laundry and Dragon is sleeping near the back step (a scene which takes more of an omniscient camera view than the first-person view of the mice), he doesn't come across nearly so horrifying. Part of this may be due to him being drugged at the time, but it also comes across as him seeming a normal cat here but a monster in all his other scenes because that is how a cat would look and sound to a mouse. (See Translation Convention.)
  • The Dreaded: He's truly monstrous and feared by all the woodland animals, save for the rats who know how to pacify him.
  • Fat Bastard: Very corpulent and very mean to boot.
  • Handicapped Badass: He's blind in one eye, but it doesn't make him any less effective as a menace.
  • Hero Killer: He's the one who kills and devours Jonathan Brisby.
  • Names to Run Away from Really Fast: His name is Dragon, which is fitting for a gigantic, monstrous predator.
  • Our Dragons Are Different: Not just in name but in his role in the story.
  • Translation Convention: In an interesting variation, Dragon's meows are rendered (except in a brief scene centered on the humans) as horrific, dragony roars to reflect that, as far as his prey is concerned, he lives up to his name.
    • Mouse ears are attuned to higher-pitched sounds than humans. A cat's yowls could quite plausibly be at the far low-frequency end of Mrs. Brisby's range of hearing, even though they'd sound high and plaintive to humans.
    • In the scene when Mrs. Brisby is imprisoned in the cage, and Mrs. Fitzgibbon goes to let Dragon in the back door, we hear him make perfectly normal feline meows. Like the scene where she's hanging the laundry, this moment is shown from more of an omniscient viewpoint than Mrs. Brisby's first-person angle, suggesting we're not seeing things from a mouse POV anymore.

    The Great Owl
"Why have you come?!"
Voiced by: John Carradine
A wise, ancient owl who is seen as something of an oracle by the other woodland creatures.
  • Abnormal Limb Rotation Range: His head is first seen 180 degrees upside down, before he slowly rotates it back into place. This is Truth in Television, as owls really can turn their heads that far because they can't turn their eyes.
  • Always a Bigger Fish: How he's introduced. A large very ugly spider tries to eat Mrs. Brisby, and the owl crushes it underfoot.
  • Artistic License – Biology: He's heard flapping his wings when he leaves his tree. Being nocturnal hunters, owls' wings are silent as their feathers greatly reduce the noise caused by turbulence.
  • Badass Baritone: The booming voice of John Carradine is dipped in a rich reverb, to make him sound even more otherworldly and imposing.
  • Big Ol' Eyebrows: The feathering above his eyes looks like a pair of large, bushy eyebrows.
  • By the Lights of Their Eyes: His eyes glow, illuminating his lair inside his tree. This is somewhat accurate as owls do have light-reflectant eyes.
  • Carnivore Confusion: Lampshaded: "Owls eat mice!" "Uh...only after dark." There are bones strewn about the Owl's lair. Owls compact all waste into a pellet-like solid, bones and all (though these are probably from disintegrated pellets; the Owl isn't too concerned with tidying his lair). The Owl seems to be completely nonplussed by this mouse but he'll gladly eat a passing bug.
  • Cobweb Jungle: The Great Owl's lair. The Great Owl himself, come to mention it. Hey, it looks awesome!
  • Creepy Good: He's covered in cobwebs from head to toe, can turn his head 180 degrees upside down, and kills small animals while maintaining a civil conversation with Mrs. Brisby.
  • Dark Is Not Evil: He's scary, but neutral. And firmly allied to Nicodemus.
  • The Dreaded: By the woodland animals, for obvious reasons—Mr. Ages even says that no one has ever seen the Owl and lived to tell it. Which makes you wonder why Auntie Shrew recommended Mrs. Brisby to seek his advice in the first place.
  • Foreshadowing: The Great Owl is the first one to reveal to Mrs. Brisby how important her husband was. He only gave her the needed advice once he learned she was Mrs. Jonathan Brisby.
  • Giant Flyer: From the perspective of the other animals in the movie, he's a giant.
  • Handicapped Badass: Downplayed; he seems to have a noticeable limp on his right leg due to old age, but this doesn't do much to hinder his flying and hunting ability.
  • Inexplicably Awesome: How he knows of the rats or why he has glowing eyes is never explained. He's clearly not an experiment subject (all other test subjects seen are mammals, and owls apparently have never been used by Nimh in real life).
  • Ominous Owl: He has Glowing Eyes of Doom, he lives in a dark lair, he's badass enough to crush a Giant Spider, and he could make a midnight snack out of most of the cast at any time. However...
  • Our Dragons Are Different: While Dragon the cat embodies the hostile and predatory version, the Great Owl is more akin to a neutral and sage-like version.
  • Pet the Dog: Before knowing who he was talking to was Ms. Brisby, he was willing to let her go. Possibly out of respect for coming to him in the first place.
  • Put on a Bus: Nowhere to be found in the sequel despite Tim's efforts to seek him out.
    Farmer Fitzgibbons
Voiced by: Tom Hatten
The owner of the land that the Brisby family and the Rats of NIMH are currently living on.
  • Creator Cameo: In a way- Don Bluth himself served as the live-action reference model for Fitzgibbons.
  • The Heavy: Sort of. The threat of his plow is what kicks off the plot.
  • Obliviously Evil: He's not actively malicious at all, just a farmer doing what he does best. He sees his annual harvesting as no more than simple job that has to be done for his livelihood, but in the field animals' point of view, it's literally Armageddon.

Voiced by: N/A (original film), Kevin Michael Richardson (sequel)
A silent, imposing soldier who guards the entrance to the Rosebush Senate chamber.
  • Adaptational Villainy: In the movie, Brutus, while he isn't a villain, scares Mrs. Brisby away from the rosebush while in the book he just gives her a hard time about it before he ultimately lets her in. The book also makes it more clear that it's just an act and Brutus isn't really mean, although he does try and help pull up the Brisby home later in the film, too.
    Mrs. Brisby: (nervously) "But what about the rat at the entrance? I can't go back there... I can't."
    Mr. Ages: (mumbling dismissively) "Oh that's just Brutus, never mind him. Now, come on."
  • Badass Baritone: Kevin Michael Richardson lends his powerful bass voice as Brutus in the 2nd film.
  • Blade on a Stick: Brutus was first seen carrying an electrified spear that he used to great effect at chasing away Mrs. Brisby from the entrance hall.
  • Gentle Giant: His real persona after work shift, at least abiding by the sequel.
  • Hidden Heart of Gold: He's revealed as such in the original novel. The original film, which makes him far more intimidating, at first only vaguely hints to this ("Oh, that's just Brutus..."), but he does try to help pull up the Brisby home; you hardly see him, and wouldn't know it was him if Justin hadn't called out his name, but he's there.
    Justin: I'll get a line around the stones, now...Brutus, quick! Get some rope; tie off those block lines!
  • Punch-Clock Villain: Brutus' job was to protect the Rosebush from anyone that would dare to enter their home without an invitation or the permission of either Mr. Ages or another Rat of NIMH simply by chasing them out of the main foyer.
  • Suddenly Voiced: He never spoke a word in the original, but in the sequel he has several lines of dialogue.
  • Took a Level in Kindness: The sequel fully shows Brutus beneath his shadowy act, where he is near unrecognisable as a goofy Gentle Giant.
  • You Don't Look Like You: In the sequel he essentially looks like a bigger built colour-swap of Justin, a far cry from how he looked in the original. Justified as his original design was a sinister disguise to scare away intruders.

"Sorry. We tend to take ourselves a little too seriously."
Voiced by: Peter Strauss (original movie), William H. Macy (sequel)
A noble, chivalrous soldier who serves as Captain of the Guard for the Rats of NIMH.
  • Badass Baritone: Downplayed. As voiced by Peter Strauss, he has a warm, slightly deep voice.
  • Badass Teacher: Becomes a mentor to Timmy in the sequel.
  • Beware the Nice Ones: As friendly and affable as he may be, he will not stand for injustice, and will valiantly defend the weak. He proves himself a formidable swordsman in his duel with Jenner. And one who will kill if he has to.
  • Beware the Silly Ones: Justin's pretty easygoing and spends most of his time kidding around, which Mr. Ages points out to Mrs. Brisby when he mentions how Justin bothers Nicodemus with his goofiness. But he's the captain of the guard for a reason, because he's a skilled swordsman and a capable leader when the situation calls for it.
  • Deadpan Snarker: In an unusually light-hearted and playful way but no less sharp for it.
    Jenner: The Thorn Valley Plan is the aspiration of idiots and dreamers! We... (sees Justin and Mr. Ages and chuckles) We were just talking about you.
    Justin: Well that's refreshing, Jenner. Usually you're screaming about us.
  • Deuteragonist: As soon as he appears, he is the second main character after Mrs. Brisby. The climax with Jenner involves Justin stopping him.
  • Foreshadowing: After Jenner lays out his plan to stage Nicodemus's death, Sullivan asks:
    Sullivan: (nervously) "But what about Justin?"
    Jenner: (evil grin) "Leave him to me..."
    (continues to echo softly) "to me... to me... to me..."
  • Klingon Promotion: He assumes leadership of the rats of NIMH in the aftermath of Nicodemus's death.
  • Nice Guy: Justin is heroic, kind, and brave.
  • The Not-Love Interest: Despite a brief moment that could pass as Ship Tease between him and Mrs. Brisby, their relationship stays platonic throughout the film.
  • Once Done, Never Forgotten: Invoked. His suggestion to Mrs. Brisby that she remove her cape. The action also highlights Mrs. Brisby as a Half-Dressed Cartoon Animal.
  • Precision F-Strike: "Damn!", an attempt to Avoid the Dreaded G Rating. (It didn't work.)
  • Shut Up, Hannibal!: During his fight with Jenner.
    Jenner: I've learned this much; "Take what you can, when you can".
    Justin: Then you've learned nothing!
  • Spared by the Adaptation: He supposedly died in the novel by getting poisoned by NIMH. He gets better in the book's sequel.
  • Tenor Boy: William H. Macy lends his tenor voice as Justin in the sequel.
  • Undying Loyalty: He's completely loyal to Nicodemus and his projects for the rats' future.
  • You Dirty Rat!: Completely inverted - Justin is not only as clean as he can be, but also heroic, courteous and kind. He's also designed to be as dashingly handsome as you can make a rat and still be recognizable.

"We can no longer live as rats. We know too much."
Voiced by: Derek Jacobi

Nicodemus is an old prophet and the wise, mystical leader of the rats.

  • Adaptational Badass: In the book, he was just an average middle-aged rat with an eyepatch (who happened to be the leader). In the movie, he's an ancient mystical seer.
  • Age Lift: Nicodemus appears very old, considering the injections given to the rats slowed their aging. In the book, he was presumably about the same age as them.
  • All-Powerful Bystander: He spends most of the film spying on Mrs. Brisby, but doesn't help her out until she directly finds him. The only plausible explanation is that Nicodemus couldn't risk extending his hand to Mrs. Brisby first while the Thorn Valley plan was still being debated for fear of his political enemy Jenner accusing him of going soft or senile or mad and using it as an opportunity to gain power.
  • By the Lights of Their Eyes: Similar to the Great Owl above.
  • Cool Old Guy: He is obviously very aged by the time Mrs. Brisby meets him, and even appears to have wrinkled hands during the flashback to the escape from NIMH.
  • Crystal Ball: Essentially, Nicodemus's whirling bronze portal-thing, which allows him to scry on others from a great distance.
  • Dark Is Not Evil: He's the film's Big Good, but not only is he scary and ugly, but also actually quite dark in himself (largely thanks to the fact that the colours in the movie are quite dull and brown, as was the style in fantastic films of the time).
  • Death by Adaptation: Near the end of the film, Nicodemus is killed by Jenner. This does not happen the novel, as Jenner had already left the rats and Nicodemus goes to Thorn Valley in the end.
  • Mentor Occupational Hazard: The leader of the rats, who ends up being killed off. Don Bluth even mentioned that this was done to develop Justin's character.
  • Mr. Exposition: But he actually does it well.
  • Off-Model: During his "we know too much" speech to Mrs. Brisby, at one part his eyebrows inexplicably disconnect from his head for a few frames!
  • The One Who Wears Shoes: The only one of the animal characters to do so in the original film.
  • Power Glows: He's the king of Glowy Thingies of Power.
  • Sacrificial Lion: He ends up murdered by Jenner in a staged accident, specifically getting crushed under the Brisby family home.
  • Squishy Wizard: Although he has great magical powers, he's old and slow.
  • Tenor Boy: Derek Jacobi lends his deep tenor voice as Nicodemus in the 1st film.
  • Wizard Beard: He has a long beard and is a Sorceror King.

"No taste for blood, huh? They've taken the animal out of you."
Voiced by: Paul Shenar
A political rival of Nicodemus who seeks to claim leadership of the rats for himself.
  • Adaptational Villainy: He was a minor character in the book who doesn't even appear in person. From what we do learn about him, he's a grump who nevertheless was a close friend of Nicodemus despite their differing views and was one of the masterminds behind their escape from NIMH. Jenner never resorted to harming anyone, and Nicodemus expresses concern for him after his departure. The movie bumps him up to an on-screen role as the villain, and he kills Nicodemus and fatally wounds Sullivan when Sullivan helps Justin.
  • Ax-Crazy: Clearly not mentally stable to begin with, and completely loses it and turns into a snarling feral beast when he sees Mrs. Brisby's stone.
  • Big Bad Wannabe: In the big picture, NIMH is the real threat of the film next to Fitzgibbons's plow. Jenner is a nasty piece of work himself, but most of his time is spent plotting a coup, and while his plan to take control of the Rats does a lot of damage when he succeeds in killing Nicodemus, it ultimately goes down in flames when Mrs. Brisby reveals NIMH is on their way to destroy the Rats, and he breaks down into a feral state and tries to kill Mrs. Brisby for jeopardizing his plan, instead of realising that his plan was doomed from the start.
  • Blood Knight: When he first meet him, he's advocating for outright war with NIMH.
  • Cape Swish: Performs this with his Ominous Opera Cape in the rat's council hall (Which one feels he picked up from Maleficent).
  • Cool Sword: One with jagged edges he makes good or rather bad use of it.
  • Diabolus ex Machina: Jenner serves this role in the film. He's introduced relatively late in the film note  and has less than six minutes of screentime, and all he contributes to the plot is providing yet another source of trouble for Mrs. Brisby and the other Rats. In his book "The Art of Storyboard", Don Bluth even said Jenner's role was solely to provide another obstacle for Mrs. Brisby.
  • Evil Eyebrows: Go on, look at them, its not like anyone who looks at him can ignore them.
  • Evil Gloating: When Justin realizes that he killed Nicodemus and accuses him, Jenner, who has grown progressively unhinged, simply can't resist spilling the beans.
    Justin: It was you. You did it. You killed Nicodemus. That was no accident.
    Jenner: Yes! I killed him. He wanted to destroy everything! I've learned this much: take what you can...when you can!
  • Evil Is Hammy: Paul Shenar really brings on the ham during the scene where Jenner voices his disapproval of the Thorn Valley plan, Cape Swishes and all. There's also the scene where he informs his minion, Sullivan, of his plan to kill Nicodemus ("Cut the lines, and the WEIGHT of it will crush his BONES!").
  • Evil Sounds Deep: Knowing that Paul Shenar went on to play Alejandro Sosa in Scarface (1983) makes his imposing baritone all the scarier to listen to.
  • Evil Will Fail: He's the one character in the movie who could truly be considered evil. And his plans are doomed from the start.
  • Failure Is the Only Option: His is a rat who wants to fight back against humans coming after them. Even if he suceeded in his plans to rule the Rats he was doomed since he fighting back against the humans was only going to get him killed.
  • Family-Unfriendly Death: He gives one to Nicodemus and then to Sullivan. See In the Back.
  • Fangs Are Evil: To set him apart from the other rats, his teeth are pointed.
  • Fantastic Racism: It's implied that he harbors this towards humans .
  • Faux Affably Evil: Jenner is possessed of a singular charm and charisma that makes it easy to see how he manipulates others around him. However, almost all of his charm and courtesy towards others is solely to meet his ends, and when things start to turn against him he devolves into a feral creature, and there is no one he won't kill in cold blood to keep his plan in motion.
  • Hate Sink: Unlike the other Rats of NIMH, Jenner is a selfish, ungrateful, sociopathic bastard designed to be as despicable as possible, desiring nothing but power and displaying a vehement opposition to "The Plan", which is a way for the Rats to live without stealing. When Mrs. Brisby, the widow of fellow NIMH escapee Johnathan Brisby, comes to the rats asking for help to move her house and her family out of the path of the farmer's plow, Jenner deliberately sabotages the moving of the Brisby house so that Nicodemus, the wise and kind leader of the rats, is killed in the process, not caring that Mrs. Brisby's children are trapped inside, and attacks Mrs. Brisby when she warns about NIMH's coming. When his henchman Sullivan turns on him, Jenner slashes him across the stomach and then attempts to kill his rival, Justin, while declaring his sole belief: "Take what you can when you can." It's very satisfying to see him fatally stabbed twice in the span of a minute, the latter being from a dagger thrown by Sullivan. Even then, the results of his actions nearly doom Mrs. Brisby's children when the house sinks into the mud.
  • In the Back: Sullivan kills him by throwing a dagger into his back.
  • It's All About Me: Jenner only cares about staying in the rose bush for as long as he likes, has no qualms about stealing and is perfectly willing to murder anyone who stands in his way in cold blood.
    Jenner: I've learned this much: take what you can, when you can!
  • Jerkass: The easiest way to sum up his unscrupulous, hate-driven personality.
  • Karmic Death: His backstabbing of Nicodemus comes around in a very grizzly fashion — he himself is stabbed in the back (quite literally, too) by Sullivan.
  • Killed Off for Real: In the book, his namesake gets killed off-screen. In the movie, he dies from a combo of Justin stabbing him in the gut, and Sullivan flinging his dagger right into his back.
  • Knight of Cerebus: Bear in mind that the film was already dark enough with Mrs. Brisby's quest to save her fatally ill son, Timmy. When Jenner shows up everything goes downhill when he succeeds in murdering Nicodemus and Mrs. Brisby's kids nearly die because of his actions.
  • Lack of Empathy: Shows zero remorse or gratitude to Jonathan Brisby's memory and when he succeeds in dropping the Brisby house on Nicodemus, killing him, is perfectly content in leaving Mrs. Brisby's kids trapped inside where they would almost certainly die.
  • Lust: Nicodemus realizes too late that Jenner has been consumed by his lust for power.
  • Manipulative Bastard: Convinces the rats to support moving Mrs. Brisby's house, so he can cut the ropes and use it to crush Nicodemus.
  • Meaningful Name: "Jenner" means "cunning" or "ingenuity", befitting of his cunning status.
  • Meaningless Villain Victory: He succeeds in killing Nicodemus, who he was convinced meant to destroy everything they had built, and meant to take control of all of it for himself. He intends to rule over the Rats from the safety of the rose bush and to even start war with the humans on the farm, and almost immediately after Mrs. Brisby comes to warn everyone that NIMH is coming to destroy them, and his plan effectively amounted to suicide for himself and the Rats. Unfortunately, Jenner is far too blinded by his lust for power to see the even worse danger coming.
  • Motive Decay: Jenner spends most of his screentime planning to usurp leadership of the Rats of NIMH by murdering Nicodemus in a staged accident. Shortly thereafter he goes berserk and he tries to kill Mrs. Brisby when she brings news that NIMH is coming, but once he sees the Amulet that Nicodemus gave her, Jenner, he forgets everything else and abruptly reveals that he knew about the stone, coveted and his goal becomes killing Mrs. Brisby for it.note 
  • Obviously Evil: Wears an Ominous Opera Cape, with Big Ol' Eyebrows that he's constantly arching, and has a long goatee. He may as well walk around wearing a sign around his neck saying "Evil Megalomaniac."
  • Ominous Opera Cape: One of the signs that he's not to be trusted. He also uses it for an impressive Cape Swish but is practical enough to untie it when he goes on a killing spree.
  • Red and Black and Evil All Over: Has black fur, red garment, combined with the aforementioned black cape with a red underside, and is rotten to the core.
  • The Sociopath: Power-hungry, cold-blooded, and perfectly willing to kill to get what he wants.
  • Sore Loser: After getting stabbed and losing the duel to Justin, he tries to kill him as Justin tells the other rats that they will head to Thorn Valley.
  • The Unfettered: He takes completely insane extremes to make sure the rats hold their post in the thorn bush, refusing to budge even from claims against their survival if they stay. When Mrs. Brisby tries to warn them that NIMH will come for them, he resorts to trying to physically silence her.
  • Villainous Breakdown: When Mrs. Brisby tries to warn the other Rats that NIMH is coming, Jenner sees it as a threat to his newfound conquest, calls her a liar and tells her to shut it and even tries to kill her out of fear that she'll ruin his plan. And then he sees the Amulet Mrs. Brisby is wearing, and he completely descends into a feral animal as Justin steps in to protect her from him.
  • Would Harm a Senior: Has no qualms about killing an ailing Nicodemus. He also viciously shoves Mr. Ages (a cripple) aside when he tries to stop him from attacking Mrs. Brisby.
  • Would Hit a Girl: He doesn't hesitate to strike a much smaller Mrs. Brisby and even tries to kill her for feeling his coup was threatened.
  • Would Hurt a Child: It's obvious that he cared nothing of the lives of the Brisby children that were stuck in the house when he causes it to fall, nearly killing the kids in the process.
  • You Dirty Rat!: While almost all of the rats in the film invert this trope, Jenner plays this frighteningly straight.

Voiced by: Aldo Ray
A rat senator who reluctantly aids Jenner in his coup against Nicodemus.
  • Actual Pacifist: When Jenner hatches a plan to murder Nicodemus and make it look like an accident, Sullivan agrees to it but is reluctant to do so and wants to back out at every step of the way. Eventually he redeems himself while dying by throwing a dagger into Jenner's back.
    Jenner: No taste for blood, eh? They've taken the animal out of you.
  • Adaptational Villainy: In the books, Sullivan is an extremely minor character who never associated with Jenner.
  • Death Equals Redemption: After being cut across the gut by Jenner, Sullivan uses his last breath to throw a dagger in Jenner's back as he prepares to kill Justin.
  • The Dragon: To Jenner, until the end, where's he's had enough of Jenner's lunacy and tries to stop him from completely going over the edge. He then gets his gut slashed for his troubles, but uses his last breath to redeem himself by throwing a dagger into Jenner's back.
  • Everyone Has Standards: While he's pretty dismissive towards Brisby's situation, he shows no joy in Jenner's plan to murder one of their own for power.
  • Fantastic Racism: Calls animals that aren't a part of the NIMH rats "lower creatures", likely due to them not being as intelligent as the rats are.
  • Family-Unfriendly Death: By Jenner, who cuts him across the belly for aiding Justin.
  • Heel Realization: He has one at the last moment when he refuses to help Jenner make Nicodemus's death look like an accident.
  • Last Breath Bullet: Dagger, actually. With the last atoms of his life, he throws it into Jenner's back before the crazed rat has another chance at attacking Justin.
  • Minion with an F in Evil: Sullivan doesn't really do anything to further Jenner's plots. He can't bear the thought of killing Nicodemus and refuses to swing his sword at the crucial moment, leaving Jenner to do the deed himself. He even tries to stop Jenner from going over the edge and gets cut across his midsection for his troubles. He lives just long enough to redeem himself by tossing his dagger into Jenner's back.note 
  • Small Role, Big Impact: Despite having little screentime, Sullivan acts as Jenner's right-hand, but is the one who finally puts a stop to him at the end of the film.
  • Someone Else's Problem: When Ages tries to convince the council to aid Mrs. Brisby, Sullivan openly objects:
    Sullivan: We have urgent problems of our own! Let the lower creatures fend for themselves!
  • Taking You with Me: Jenner cuts him down for betraying him by loaning Justin his sword. Sullivan returns the favor only minutes later by tomahawk-tossing his dagger into Jenner's back, to stop him from killing Justin.

    Jonathan Brisby
Voiced by: N/A
Mrs. Brisby's late husband, and one of the few mice to survive the escape from NIMH.
  • The Ace: Everyone talks about how great he was, and the Great Owl had a very high degree of respect for him.
  • Disappeared Dad: To his four children he had with Mrs. Brisby. After drugging Dragon's food dish one time too many, Dragon ate him.
  • Posthumous Character: He was killed before the events of the film, and him being a mouse of NIMH is a driving force of the plot.
  • The Voiceless: Whenever he is shown in a flashback, he is shown without dialogue.

Voice by: N/A
The National Institute of Mental Health, a biomedical research agency for the United States government, responsible for the creation of the Rats and Mice of NIMH.
  • Bait-and-Switch: They're more prominent in the sequel, and a few scientists even appear on-screen rather than being The Ghost, as in the first movie. One is even named, Dr. Valentine. However, one the action actually shifts to NIMH, it's quickly revealed that Martin's been experimenting on them.
  • For Science!: Nicodemus believes that NIMH performed their uplifting experiments simply to sate their scientific curiosity rather than any real purpose.
  • The Ghost: Other than a few NIMH workers shown capturing the wild rats in Nicodemus flashback, they don't really appear in person.
  • Humans Are Cthulhu: The Rats can only guess why the researchers grabbed them from their natural homes and subjected them to all manner of painful and horrific experiments.
  • Oh, Crap!: Seems to have been their reaction when the Rats escape was discovered. They've been trying to find and exterminate their creations ever since.

    Jenny McBride
Voiced by: Hynden Walch
A female mouse from NIMH 2 who goes on a quest with Timmy to save her imprisoned parents.

Voiced by: Meshach Taylor
A caterpillar from NIMH 2 who is a con artist but helps Timmy and Jenny on their quest to NIMH.
  • Agony of the Feet: Jenny steps on Cecil's foot to intimidate him take them to the Great Owl.
  • Butt-Monkey: Like Jeremy, he suffers misfortunes.
  • Comedy Duo: With Jeremy in the sequel.
  • Con Man: He is a con-artist who scams the animals out of their money.
  • Cowardly Lion: As much as a coward as Jeremy is, he refuses to go with Timmy and Jenny in NIMH.
  • Jerk with a Heart of Gold: Despite being a con-artist and a coward, he helps the protagonists in their goal.

Alternative Title(s): The Secret Of NIMH 2 Timmy To The Rescue