I just realized that I never replied to this thread

Especially when it says "all the world will be your enemy, prince with a thousand enemies." I don't know why that's so powerful right then but it is.
This happens twice in the film: once in the prologue, and once at the end. While I really liked the prologue, I found the repetition of the line at the end to be rather annoying

The Black Rabbit is a lone rabbit and doesn't have an Owsla, but El-ahairah does 
The story of El-ahrairah and the Black Rabbit of Inlé told by Dandelion in the book mentions the Black Rabbit's owsla.
I like to think that the movie was implying that Elahrairah and Inle were infact the same rabbit all along. This rabbit symbolizes that life can't exist without death and death can't exist without life. And the characters Elahrairah and Inle are just the rabbits way of comprehending that.
An interesting theory

Anyway, I agree that it was El-ahrairah in the book, but in the film it appears to have been changed to the Black Rabbit.
One thing I find interesting though: the Film Picture Book, which features stills from the film with captions by Richard Adams. I don't have a copy myself, but I remember reading somewhere that the picture book explicitly states that it was El-ahrairah who came for Hazel. But then, the picture book appears to have also undone a few other changes mentioned in the film (no mention of Violet, and the plant stolen by Toadflax at the beginning is a cowslip and not a coltsfoot).