Watership Down may be the only novel ever written about the epic struggle of a colony (tribe? warren?) of rabbits, but once past the initial suspension of disbelief, it's a great read-- with its own language (an automobile is called a "hrududu" because of the sound it makes) poetry, mythology, politics, and British style sociology.
One might have thought that turning this allegorical novel into a film would be impossible for anyone but Disney, but this 1978 film is a British production, which begins in a primitivist visual style, then shifts into a kind of watercolor-influenced cel animation that is easy on the eye but more subtle than a typical Lady and the Tramp type kid's film. The plot and language are also far more adult, since the author is really commenting on the passivity and pessimism of postwar Britain, so the piece has something for all ages. Occasionally dated, but both charming and thoughtful.