The character of the gatekeeper, “Brutus,” is not credited among the onscreen “voice talents,” as he has no spoken lines.
       Contemporary sources referred to the film throughout production as Mrs. Frisby and the Rats of NIMH, Mrs. Frisby and the Rats of N.I.M.H., and The Secret of N.I.M.H., though its domestic release title was The Secret of NIMH.
       On 19 Sep 1979, Var announced that writer-director-producer Don Bluth joined seven animators and four assistant animators in leaving their positions at Walt Disney Productions to form Don Bluth Productions. The independent animation studio would produce its first feature film, a $7 million production of the 1971 Robert C. O’Brien novel, Mrs. Frisby and the Rats of NIMH, in association with Aurora Productions, the newly-formed production company of former Disney executives Rich Irvine, James L. Stewart, and Jon Lang. Lang, however, does not receive onscreen credit for The Secret of NIMH. A WSJ article published the same day reported that Bluth’s animators left Disney after the studio passed on Mrs. Frisby and the Rats of NIMH, as the studio already possessed film rights to a number of popular novels and had “no incentive to buy…or work on anything new.” Production notes in AMPAS library files reported that Bluth obtained the rights to O’Brien’s novel in 1979, and in 1980, moved from his home garage to a larger office space to begin searching for additional animators and voice talent. WSJ noted that Bluth’s Studio City, CA, headquarters hoped to continue hiring after expanding to thirty employees, eighteen of which came from Disney.
       At the onset of production, filmmakers conceded that their biggest struggle would be finding a way to make rats appealing. Animation was estimated to cost roughly $80-85,000 per minute, and promotional materials revealed that the project would be filmed four times in its entirety: once in sketch form, once in rough animation, once in final pencil animation, and once in color.
       Almost a year later, the 6 Aug 1980 Var included Mrs. Frisby and the Rats of NIMH among thirteen features that gained exemption from the Screen Actors Guild (SAG) strike under an interim agreement. According to the 22 Oct 1980 CSM, the film used two electronically-operated multi-plane cameras, allowing several layers of animation to be shot simultaneously for a more three-dimensional image. The article expected the project to contain 6,000 feet of film, created by a thirty-eight person staff over the course of three years. Promotional materials suggested that the film contained more than 600 colors, nearly 500 of which were developed by Bluth’s studio. As opposed to live-action film projected at a rate of twenty-four frames per second, the animation contained ninety-six drawings per second, totaling over 1.5 million drawings.
       The 10 Jun 1981 Var announced that animators were at the “midway” point of the thirty month production schedule. A 27 Jul 1981 HR story stated that in order for to meet United Artists’ late Jun 1982 domestic release date, 2,500 feet of film still needed to be completed before 4 Jun 1982. This article reported a $6.1 million budget, and stated that the project contained 1,000 background paintings and 1,200-1,600 drawings, produced at a rate of two to four images per artist, per hour. Although the theatrical release was eighty-two minutes in length, the original runtime was estimated between seventy-five and eighty minutes. At this stage of production, the title had also been changed to The Secret of NIMH, while the main character of “Mrs. Frisby” was renamed “Mrs. Brisby,” due to copyright conflicts with Frisbee toy manufacturer, Wham-O.
       Additional press materials stated that Bluth, John Pomeroy, and Gary Goldman cast Dom DeLuise after watching the actor in a televised performance of his 1978 film, The End (see entry). A 19 Oct 1981 DV brief reported that Hermione Baddeley had arrived in Los Angeles, CA, to record her voice-over for the film, but was suddenly called back to London, England, to complete work on two previous commitments.
       According to a 29 Dec 1982 Var article, Bluth raised The Secret of NIMH’s final $6.5 million budget from private financiers outside the film industry after investing $250,000 in the costs of his new studio. A 12 Aug 1981 DV article reported UA’s settlement on a low 22.5% domestic distribution fee. While only providing $600,000 of production costs, Aurora expected to front an additional $4.4 million in prints and advertising through the corporate entity, Mrs. Frisby Ltd. As stated in DV, Mrs. Frisby, Ltd., was to be repaid from the film’s grosses after production loans had been reimbursed. However, the 29 Dec 1982 Var claimed Metro-Goldwyn-Mayer (M-G-M), which had formed a merger with UA in 1981, “had no faith” in the project and chose to release the film in a “rollout campaign” starting on the West Coast and moving East. Bluth was forced to independently raise $4.2 million through private funding for M-G-M/UA’s advertising campaigns. In addition, the 12 Aug 1981 DV claimed that Aurora was perpetually guaranteed 15% of all distribution and merchandising profit. M-G-M/UA’s distribution rights were fixed to expire after sixteen years; provided that the company reissued the film within the first eight years of the deal, M-G-M/UA would be granted the option to renew distribution rights for an additional five years. An 18 Apr 1982 HR article announced that The Secret of NIMH was scheduled to open in 1,000 theaters 2 Jul 1982 by M-G-M/UA Entertainment Corp., and reissued the following Christmas.
       On 16 Oct 1981, UA announced a licensing agreement with Western Publishing Company to produce a range of children’s book and game products, which would be introduced at the Frankfurt Book Fair in Frankfurt, Germany, later that month. In addition to Western, the 25 May 1982 HR noted that Scholastic, Antheneum, and Antioch publishing companies would promote book tie-ins at the American Booksellers Association Convention in Anaheim, CA, 28 May—2 Jun 1982. On 29 Jan 1982, a UA press release in AMPAS library files stated that the R. Dakin Company planned to debut a line of plush toys at the American Toy Fair in Feb 1982 before releasing them for general sale in Jun 1982. The 18 Apr 1982 HR reported additional merchandise deals with General Cinema, Circle K, Macy’s, and J. C. Penney stores. As stated in a 13 Apr 1982 UA announcement, Bresler’s 33 Flavors ice cream shops collaborated with M-G-M/UA and Quinn, Brein & McCarthy, Inc. Marketing and Management Services of Santa Clara, CA, to create a special ice cream flavor promoting the picture.
       A 10 Mar 1982 M-G-M release stated that members of the press would screen thirty minutes of the film at the studio before being escorted to the Don Bluth Productions headquarters to observe the animators at work; the event was part of a 15—18 Mar 1982 assembly promoting The Secret of NIMH and Victor/Victoria (1982, see entry). According to the 21 May 1982 HR, the American Film Institute hosted a day-long seminar on 29 May 1982 titled, “Creating an Animated Feature: The Secret of NIMH,” which contained slides and clips from the motion picture.
       A 2 Jul 1982 UA press release indicated that Bluth, Pomeroy, and Goldman planned to separately tour multiple U.S. cities to promote The Secret of NIMH throughout the first half of Jul 1982. A 29 Jul 1982 release announced that the film’s opening in seventy New York City theaters the following day would be accompanied by live shopping mall performances with the characters “Jeremy,” “Dragon,” and “Mrs. Brisby,” in Brooklyn, NY, and Long Island, NY.
       A 25 Aug 1982 LAT article reported that Walt Disney Studios banned multiple film buyers and theater owners from booking The Secret of NIMH as a double feature alongside the studio’s Tron (1982, see entry). Although Disney claimed that they preferred Tron to be paired with another Disney film, the article suggested that the company remained bitter over Bluth’s departure from the company. Bluth indicated interest in bringing a lawsuit against his former employer, although the pursuit of any additional legal action is undetermined.
       The 29 Dec 1982 Var reported a domestic box office gross of $12 million.
       Although Shannen Doherty's first onscreen performance was in Ron Howard's Night Shift, released 30 Jul 1982, The Secret of NIMH marked her motion picture debut.
       In 1998, M-G-M Animation released a direct-to-video sequel titled The Secret of NIMH 2: Timmy to the Rescue, but did not feature involvement from Bluth or Don Bluth Productions.