Sir Christopher Lee (King Haggard) showed up for the recording sessions armed with his own copy of the book, with several places marked to indicate things that must not, in his opinion, be omitted.
This is similar to his behavior on Le Seigneur des anneaux : La Communauté de l'anneau (2001) and its sequels in which he also showed up on set with his copy of the books, and was often a stickler for exact fidelity to the novels.
In 2010, co-Director Jules Bass revealed that Jeff Bridges called him out of the blue, volunteered to do this movie for free as the novel was one of his favorite books, and recommended his friend Jimmy Webb for the soundtrack.
Author Peter S. Beagle showed up at a recording session during the making of this movie as Sir Christopher Lee recorded King Haggard's monologue about how only unicorns brought him happiness. Lee begged Beagle for his approval of his vocal performance, offering to record it again if the author found it unsatisfactory.
A live-action version of the novel has toiled in "development Hell" over the years, though it has reached various states of pre-production at times, even with Sir Christopher Lee and Dame Angela Lansbury set to reprise their roles. As of 2013, on-going legal disputes stemming from the animated movie, coupled with budgetary issues, have stalled the project, though author Peter S. Beagle has completed a new screenplay, and still expresses hopes that the movie will one day be made.
Due to contractual disputes, author Peter S. Beagle received no compensation for the sale of any of the original DVDs or VHSs. A 25th Anniversary Edition of this movie was released by Lionsgate Home Entertainment in 2007.