When Bigwig confronts Woundwart in the warren, he says "silflay hrakah!" According to Richard Adams, author of the novel on which the series is based, "silflay" is a Lapine (rabbit) word that means "to eat outdoors" and "hrakah" is "droppings." So, an English translation could be "eat shit!"
As the rabbits are traveling through the village, there is a garden bench with a plaque on it dedicated to Richard Adams.
Lee Ingleby (Captain Campion) & Jason Watkins (Captain Orchis) also worked together on three episodes of Line of Duty (2012) as Nick Huntley & Tim Ifield respectively.