The main character's mom carves rabbits from wood in this movie. The IRL mom of the director also made rabbits out of wood because of Watership Down, and says about the novel, “I have a philosophy that — if you read it — those rabbits are so fucking persecuted. It’s just one problem after the other, and it’s so harrowing, but they stay together.”
The characters discuss the themes of Watership Down in class, plus there's like a bunny guy and that can't be coincidental
The character John says, about Watership Down, “I wish it was longer”