One of the biggest
differences between
Mrs. Frisby and the Rats of NIMH and
Don Bluth's movie is in the
climax, in which the Frisbys'
cinderblock house is moved to protect it from being
plowed up.
In the book, the rats accomplish the moving through hard work and good engineering. In the movie, the rats' block and tackle are sabotaged by a villain, and "Mrs. Brisby" uses a magical amulet to levitate the house to its new location.
It seems to me that this leaves the movie viewer with a much different message than the reader gets. In the movie, "love is the key": love itself -- Mrs. Brisby's love for her children and the late Jonathan Brisby's love for his wife -- has the mystical power to overcome insurmountable physical obstacles. In the book, it is the dedication, skill, loyalty and practicality of Frisby and the rats which accomplish what love and respect motivate.