This is a reference to the Killer Rabbit of Caerbannog (https://en.wikipedia.org/wiki/Rabbit_of_Caerbannog) in the movie Monty Python and the Holy Grail, in case you're unfamiliar with this very well-known meme. It's a hilarious scene (https://www.youtube.com/watch?v=pmu5sRIizdw).
Wikipedia entry states "The idea for the rabbit in the movie was taken from the façade of the cathedral of Notre Dame de Paris. This illustrates the weakness of cowardice by showing a knight fleeing from a rabbit."
I watched the movie with my son (11) a few weeks ago, and was wondering if he'd enjoy the sometimes dry humor: he loved it, esp. the questioning at the Bridge of Death.