The failure to get the film out in any reasonable amount of time helped bring down Ron Miller's regime at Disney, and its financial failure ensured that he would never work in Hollywood again.
Co-directors Ted Berman and Richard Rich and producer Joe Hale were also fired from Disney in the wake of the film's release; Berman and Hale never worked in animation again, while Rich ended up having to start his own studio in order to continue his career, which never saw the heights it could've had.
Inverted with Jeffrey Katzenberg, who ended up becoming more influential within Disney as a result of this film's failure; he was able to utilize his "I told you this would flop" position on the movie over the older executives who had believed in it, painting their tastes as out of touch with what current moviegoers wanted to see.
It was very nearly the death of Disney itself. Thankfully, its spectacular and humiliating failure, as well as the growing amount of competition, convinced them to finally get their act together and make better movies.
Disowned Adaptation: The author of the original novels, Lloyd Alexander, didn't really consider the movie an adaptation. Surprisingly, actually liked the film anyway (see Other Trivia below).
Dueling Movies: With The Care Bears Movie, its polar opposite. It marked the first time that a Disney animated film had gone head-to-head with a non-Disney animated film at the North American box office and lost.
It jumps straight into a very-loose adaption of the second story of The Chronicles of Prydain. Which in of itself is a very, very dangerous move.
Contrary to popular belief, the infamous cuts made to the more violent and nightmarish scenes of death, decay, and destruction weren't made because Disney believed cartoons were for kids (far from it. Had the executives not intervened, this would have been Disney's first foray into more teen- and adult-based animation). The reason was because then studio chairman Jeffrey Katzenberg didn't know about Disney's plan to make an animated movie that had more adult content in it and forced the producer Joe Hale to cut the film by 12 minutes without being given a thorough explanation first. If the original had stayed, viewers would have seen this fully uncut upon its initial premiere.
Katzenberg originally only wanted ten minutes cut, but the filmmakers only cut six minutes, feeling any more would hurt the story. It turned out that he meant literallyten minutes and, when he discovered that they hadn't met his specific demands, proceeded to personally edit out even more than he originally requested until company chief Michael Eisner forced him to back off when word of this got to him.
Franchise Killer: Disney secured the rights to the entire Chronicles of Prydain, but the film flopped so hard, it killed off any future plans of continuing the series for 3 decades.
Genre Turning Point: The film was meant to be this for animated Disney movies in general, an attempt to darken and "modernize" the studios feature film output while also proving that Walt Disney's one-vision method of film making was still viable in the 1980s. And it was a turning point... just not in the way that the film makers had hoped; its massive box office failure not only led to a trend of lighter Disney animated films (which culminated with their "true" turning point in 1989, The Little Mermaid), but also ended (most of) Walt Disney's methods as solid company policy in favor of a more "Hollywood" style of movie making (stricter deadlines, tighter budgets, more committee meetings, more executive influence, attempts on franchise integration, etc.).
Germans Love David Hasselhoff: The Horned King has plenty of attention in Japan. This may have had to do with the extinct attraction in Tokyo Disneyland. Shall we begin?
Mickey Mouse on the Game Boy in 1989 has him as the final boss.
Mickey Mouse II on the same system two years later again has him as the final boss.
Both of these games replaced him with Witch Hazel when they were converted to the Bugs Bunny Crazy Castle games.
Mickey Mouse III: Dream Balloon in 1992 again puts him as the final boss, only to be replaced by Night Mayor when it was converted to Kid Klown in Night Mayor World.
Finally appeared without alterations in Land of Illusion on the Game Gear and Sega Master System in 1993, although this time colored from older concept art and given the name of "The Phantom." And this was the only time that he appeared in North America and Europe in a Japanese produced game.
Old Shame: Disney went to great lengths to disassociate themselves from the film. For example:
They opened a Black Cauldron-themed restaurant at Disney World ("Gurgi's Munchies and Crunchies") in anticipation of the film's release. Once it bombed, they closed the place down then later remodeled it into a Beauty and the Beast themed establishment (which is now replaced with a Robin Hood establishment).
It was because of The Little Mermaid that Walt Disney Home Video didn't release it on home media sooner — according to the IMDb, Disney was all set to release it when the latter film became a smash hit and they were pressured to get it on video ASAP. Because this movie was both atypical and unpopular, it wasn't released to video in North America until 1998 as one of the last installments in the Walt Disney Masterpiece Collection. Even later, The Black Cauldron would become the Canon's last traditionally-animated movie, aside from some 1940s package films, to receive a Blu-ray release.
Overlaps with No Export for You: The Black Cauldron has never been released or dubbed in Hungary, Turkey, Israel, or Thailand (though that may also be for content reasons, as those countries do treat animated pieces like children's fare).
Stillborn Franchise: Disney actually had the rights to the entire book series. When the movie imploded, plans for any sequels and any more adaptations of the books by Hollywood were sunk for 30 years; Disney reobtained the rights and began plans to try the series again in 2016.
The Other Marty: Hayley Mills was originally cast in the role of Princess Eilonwy and hosted a behind-the-scenes special on Disney's Wonderful World in which she introduces herself as the voice of said character. Then, for reasons unknown, Mills was replaced.
Concept art on the DVD shows that the ending of the film would have been closer to the books with the Horned King being destroyed by Gwydion.
Tim Burton drew up some concept art for the film, not a single piece of which was used.note He would later claim that his drawings were never going to be used anyway. The studio just wanted to give him something to do while they debated whether or not to fire him, and he left Disney anyway. He wouldn't deal with them again until The Nightmare Before Christmas.
The cuts were made to keep it from getting the R rating because the PG-13 rating hadn't been invented yet. Imagine if the cuts weren't made.
The film is significant for the company in several ways:
It is the very first movie to have the Walt Disney Pictures logo replace the Buena Vista logo; all movies from here on out will open with said logo.
It is the first Disney animated feature to have absolutely no singing; thus, there is one less element available to alleviate the movie's dark elements.
This movie is the reason that the Disney Animated Canon exists. Prior to 1985 the Disney animated film lineup was more or less free-floating, with the 1940s package films sometimes being counted, the live action/animation hybrid films sometimes being counted, the documentaries with animated segments sometimes being counted, etc. This films release however was intended to be a landmark for Disney animation, and necessitated a label that was fitting for such an event; and so, shortly before Cauldron's release Disney finally set an official lineup for their animated movies in order to name this one their 25th feature.
A common misconception is that The Great Mouse Detective was the first animated Disney movie to use CGI. Actually, it was this movie - the Bauble, boat, explosions, and cauldron itself were animated with CGI. However, because The Black Cauldron was such a failure, most fans and critical Disney historians purposely forget this vital piece of trivia.
Despite being a massive flop, it had gotten praise from probably the last person you'd expect - the writer of the original books, Lloyd Alexander. He stated: "First, I have to say, there is no resemblance between the movie and the book. Having said that, the movie in itself, purely as a movie, I found to be very enjoyable. I had fun watching it. What I would hope is that anyone who sees the movie would certainly enjoy it, but I'd also hope that they'd actually read the book."