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; he founded the Silverado winery and moved into that business instead.
Co-directors Ted Berman and Richard Rich and producer Joe Hale were also fired from Disney in the wake of the film's release note Berman had technically retired, but Hale and Rich also allegedly took an antagonistic attitude towards both Jeffrey Katzenberg and deputy Peter Schneider, which was the other half of why they got the ax ; 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.
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.
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.
Disowned Adaptation: The author of the original novels, Lloyd Alexander, didn't really consider the movie an adaptation. Surprisingly, he actually liked the film anyway, mostly because he felt it had so little to do with his work.
Dueling Works: This movie, Legend, and The Legend of Zelda all feature the same three main characters: a young man in green clothes with a magic sword, a beautiful blonde-haired princess, and a fearsome demon-king. All three came out within a year of each other, meaning that all three were in development at the same time, and couldn't have influenced each other's development. One can only imagine Nintendo's, Disney's, and Ridley Scott's (!) reactions when they discovered what the other two had done.
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.
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).
Because this movie was both atypical and unpopular, the film was never released on home video until 1998.
Allegations about what Disney considered doing with the film in the 13 years of its reported shelving have circulated on the internet, but with very little evidence. One rumor (which as of May 2016, has not been proven) claims it was because of The Little Mermaid that it didn't come to home media sooner. 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. Another allegation was that Disney planned to reissue it in theaters several years later under a new title, Taran and the Magic Cauldron (35mm prints with this title are in circulation even if a wide release didn't occur). The only other evidence for this are posters under multiple languages, as well as children's tie-ins (picture books and puzzles), all bearing this new title.
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, this time as live action.
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 until his contract ran out. He ended up getting fired, however, when he was commissioned to make a couple of short films and turned in the incredibly bleak Frankenweenie short. He eventuallycameback.
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 (some of the footage Katzenberg had cut actually made it to the film's trailer on early copies of the 1985 VHS of Pinocchio).