- Author Existence Failure: The Film of the Book was to have been directed by John Hubley, but he died early in production and was replaced by Martin Rosen. Some of his work, such as the opening scene, remains in the finished film.
- Box Office Bomb: Though successful in the UK, the film underperformed in the US, earning under budget ($3.7 million against $4.8 million). It was mainly because of being released the same month as Halloween.
- Celebrity Voice Actor: The film has quite a handful of well-known actors, including John Hurt, Richard Briers, Zero Mostel (who isn't so well known today but was quite prolific at the time), Ralph Richardson, Denholm Elliott, and Nigel Hawthorne.
- Cut Song: Apart from "Bright Eyes", Mike Batt wrote other songs for the film which were not used. The composer recorded three songs with vocals by Art Garfunkel, but only "Bright Eyes" made it to the film.
- Executive Meddling: Sort of. According to Word of God, Bigwig really should have succumbed to his wounds after the fight with Woundwort, but the author's kids wouldn't stand for that.
- Posthumous Credit: In Zero Mostel's final film role, he recorded his parts before passing away suddenly from what has been assumed to be an aneurism, and the film was released after his passing.
- Referenced by...: The Russian video game Metro Exodus has a brief scene with two rabbits floating down a river on a raft. Video here.
- Technology Marches On: Over 40 years later, the animated film has aged surprisingly well. Because of the lack of focus on humans and all the tech you see them using (shotguns, cars), this story could have been set in 2020 and it would still essentially look the same. For all you know the humans have smartphones and are on the Internet in the house.
- What Could Have Been:
- Bigwig was supposed to die after he fought Woundwort. After the author's daughters begged him to spare him, he changed his mind.
- There were plans to adapt the book into an opera and a ballet before settling on an Animated Adaptation.
- Working Title: Hazel and Fiver.
- Write Who You Know: Kehaar was based on a Norwegian Resistance Fighter, and the rabbits that Hazel leads from the Sandleford warren are based on members of Richard Adams' unit in World War II, with Bigwig and Hazel in particular based on specific individuals.
- Written for My Kids: The book was first made up by Richard Adams as a story to tell his two daughters while he was driving them in his car. It was the daughters who persuaded him to later write the story down.
Trivia / Watership Down