Richard Adams, author of the source novel, initially told the story to his daughters while on long drives and they insisted he write the story.
Rory Kinnear, the voice of Cowslip in this miniseries, is the son of the late Roy Kinnear, who provided the voice of Pipkin in the original Watership Down (1978).
The series uses many words from the Lapine language invented by Richard Adams for the book on which the series is based. "Flay," for example, means "food" and the suffix "rah" is an honorarium meaning prince or leader. The rabbits' folk hero is called "El-ahrairah," which combines the Lapine words for enemy (Elil), thousand (hrair) and prince (rah) and means "Prince Of a thousand enemies." A full glossary of these and other words can be found in the original novel.
When Daniel Kaluuya's character Bluebell is telling the story of James McAvoy's character Hazel to the rabbit children at the end of the series, he recites the first words that Richard Adams wrote in the first chapter of the original novel.
Fiver's visions were substantially toned down from the original adaptation, which is widely criticised for being too scary.