Disney has had a stranglehold on animated feature films ever since Walt and friends made the first one, Snow White and the Seven Dwarfs, in 1937. But there have been occasional challenges to Disney's dominance over the years, none so dramatic as the one represented by Don Bluth and The Secret of NIMH. Released in the summer of 1982, at a time when Disney’s Animation Studio was struggling (these were the The Fox and the Hound/The Black Cauldron years), The Secret of NIMH saw a group of traditional animators attempt to unseat Disney—or at the very least to rattle the company out of its complacency. It was like David and Goliath, except that David lost and motivated Goliath to try harder. Here's a trove of information about everyone's favorite non-Disney animated classic. 

1. IT WAS MADE BY FORMER DISNEY ANIMATORS WHO WENT ROGUE.

In 1979, while Disney was in the middle of production on The Fox and the Hound, animators Don Bluth, John Pomeroy, and Gary Goldman left the company, joined by a handful of other members of the animation staff. They were frustrated by Disney's bureaucracy and assembly-line attitude, and they believed Disney was neglecting certain animation skills and techniques that would be vital in the years ahead, especially as their veteran artists—the legendary Nine Old Men—retired or died.

2. THE FILMMAKERS WORKED FASTER AND CHEAPER THAN THEY HAD AT DISNEY.

Disney's The Fox and the Hound cost $12 million. The Black Cauldron, released in 1985, would cost $44 million. The Secret of NIMH? A cool $7 million. Furthermore, it was produced in 30 months—half the time Disney's 'toon features took. 

3. A TOY COMPANY MADE THEM CHANGE THE MAIN CHARACTER'S NAME.

The 1971 novel from which the book was adapted is called Mrs. Frisby and the Rats of NIMH. The title was shortened for the movie, and Frisby—which is pronounced like "Frisbee"—was changed to Brisby to avoid trademark problems with Wham-O, the company that makes America's favorite flying disk.

4. DISNEY TURNED THE BOOK DOWN.

According to writer/producer Gary Goldman, animator Ken Anderson first took the book to Wolfgang "Woolie" Reitherman, Disney's chief animator. Reitherman's reply: "We've already got a mouse."  

5. THE MOVIE ONLY TELLS US ONCE WHAT "NIMH" MEANS.

It's the National Institute of Mental Health, the research facility where rats were being experimented upon. Characters in the movie only call it "NIMH" except for the very first time it comes up:

FARMER'S WIFE: Dear, a man came by today, from NIMH.

FARMER: NIMH?

FARMER'S WIFE: Yes, you know, the National Institute of Mental Health. He was asking if we had noticed anything strange about the rats on the farm...

Anecdotally, when we mentioned this on Twitter, we were surprised to find that many fans of the film never realized what "NIMH" meant. 

6. THE MOVIE NEVER TELLS US ONE IMPORTANT CHARACTER'S NAME. 

Jenner, the conniving rat who sabotages the plan to move Mrs. Brisby's home and kills Nicodemus, is assisted by a reluctant sidekick. But this beta-rat becomes conscience-stricken, turns on Jenner, and is ultimately the one who kills him. It wasn't until after the film was released that its makers realized the heroic rodent's name is never mentioned. It's Sullivan.

7. IT WAS DRAWN BY THE SAME HANDS THAT DREW XANADU'S ANIMATED SEQUENCE.

One of the first projects that Bluth's new company took on was the two-minute animated scene in Xanadu (1980), the famously bad Olivia Newton-John musical. The side project put The Secret of NIMH under an even tighter schedule, and animators were known to take cat naps under their desks while working long hours. 

8. THERE'S HIDDEN SYMBOLISM IN TWO CHARACTERS' SIMILARITIES. 

John Pomeroy, one of the chief architects of the film, said it was intentional that the Owl and Nicodemus have the same walk, glowing eyes, and speech patterns, meant to imply they were two different physical incarnations of the same mystical character. There was even some talk of having the same actor provide the voices for both characters, but it was determined that the film needed as many different celebrity voices as it could get.

9. THERE WERE MANY SIGNIFICANT CHANGES FROM THE BOOK.

Mrs. Brisby's magical amulet isn't in the book at all. As the three producers explained in a letter to a school class that asked about the changes, "The amulet was a device, or a symbol, to represent the internal power of Mrs. Brisby … A visual extension of an internal (and harder to show in a film) power."

Other alterations: Nicodemus was turned from an ordinary rat into a wizard; Jenner, merely a traitor in the book who leaves the colony, was made into a full-fledged villain; and the ending was changed so that Mrs. Brisby's children are saved by Mrs. Brisby, not the rats. 

10. DOM DELUISE TURNED JEREMY THE CROW FROM A MINOR CHARACTER TO A MAJOR ONE.

The rotund, jovial comedian was one of America's favorite funnymen at the time, thanks to his association with Mel Brooks, Burt Reynolds, and The Muppets, and his regular appearances on Johnny Carson's Tonight Show. Just as Robin Williams would do with Aladdin's Genie a decade later, Dom DeLuise expanded Jeremy the crow's role by hamming it up and improvising during the recording sessions. The producers (who supposedly all chose DeLuise for the part independently of one another) responded by incorporating his ideas into the script. DeLuise would later provide voices for several other Don Bluth productions. 

11. STUDIO POLITICS PROBABLY DOOMED IT.

Bluth and company made their deal with United Artists. But UA, after having its best year ever in 1979 (thanks to Rocky II, Manhattan, and Moonraker), fell apart completely in 1980, when Heaven's Gate proved a disastrous flop. UA's corporate owner sold the studio to another company, Tracinda, which also owned Metro-Goldwyn-Mayer; in 1982, Tracinda merged them into MGM/UA.

The new bosses weren't as interested in NIMH as the old bosses had been. The release date was moved up from late August to early July, putting it in competition with E.T., Rocky III, Star Trek II: The Wrath of Khan, Poltergeist, Blade Runner, and Annie. What's more, instead of giving the film a wide release, MGM/UA opened it on less than 100 screens and expanded very slowly—so slowly that by the time it rolled out, the advertising had come and gone and people had forgotten about it. NIMH grossed around $14 million in theaters and didn't become truly profitable until it found an audience on home video. 

12. JOHN CARRADINE DID HIS LINES IN ONE TAKE, ON PAINKILLERS.

Producer Gary Goldman told an online forum that the great John Carradine, hired to lend gravitas to the voice of the wise Owl, arrived late to the afternoon recording session and seemed to be intoxicated. Carradine's agent confided that the 75-year-old actor suffered from near-debilitating arthritis, the medication for which made him loopy. Also, the agent said, he'd probably had a martini at lunch. Goldman, Bluth, and their cohorts used coffee and conversation to get Carradine sharp again. Once he was sober, he recorded his lines, declared each delivery to be the best performance he had in him, said he wouldn't do retakes or alternate versions, and left. "Good thing he gave a great performance," Goldman said.