Sometimes a bunny is just a bunny… and sometimes it's a killer bunny. But sometimes a killer bunny… isn't just a killer bunny. A cute harmless bunny ripping the heads off of knights in a ferocious display of savagery is truly awe-inspiring as is, but if we ignored some of the symbolism and historical allusion we wouldn't be doing our job.

The idea of the Killer Rabbit was reportedly taken from a carving in the Notre Dame cathedral in Paris which depicts a knight running away from… a rabbit.

Maybe he was a smart man running from a murderous hare, but more than likely it was representative of cowardice, a bunny being just about the least threatening animal imaginable. This is not something you'd want on your resume as a knight. (At least this Notre Dame knight didn't pull a Robin; his armor looks to be unsoiled.)

In The Holy Grail, however, fleeing from a rabbit is less about being a coward and more about the knights' stupidity. Tim tries to warn them but they're deceived by the innocent, furry little guy.

Also: does this remind you of the Trojan rabbit trick that Bedevere & Co tried to pull earlier? That also involved a rabbit—a rabbit whose most deadly weapon was its harmless appearance. And we see the knights outsmarted by the French who, realizing the deception, re-gift the rabbit in projectile form. It crushes one of the servants, making it another killer rabbit.

So the rabbit seems to become a subversion of its original intention. It no longer references cowardice but hubris—the failure to recognize that you are outmanned (or outrabbited, as the case may be).