The Secret of NIMH

The Secret of NIMH is a 1982 animated feature film made by Don Bluth, and is based on the book Mrs. Frisby and the Rats of NIMH. In 1998 it was followed by a direct-to-video sequel, The Secret of NIMH 2: Timmy to the Rescue, in which Don Bluth was not involved.

Changes from the book
Fearing legal issues from the similarity of the name Frisby to that of the Frisbee toy, Don Bluth to change the name to Brisby. This decision was made after many of the film's lines had already been recorded, which required extensive editing to change the f sounds to b sounds. Whereas the novel was something of a mild, modern science fiction story, the film incorporated a number of medieval and fantasy elements, most notably in its depiction of the Rats of NIMH.