Per Monty Python & The Holy Grail….
King Arthur and his knights are led to the cave by Tim the Enchanter (John Cleese) and find that they must face its guardian beast.
Tim verbally paints a picture of a terrible monster with "nasty, big, pointy teeth!", so terrifying that Sir Robin soils his armour at the mere description.
When the guardian appears to be an innocuous white rabbit, surrounded by the bones of the fallen, Arthur and his knights no longer take it seriously.
Ignoring Tim's warnings ("a vicious streak a mile wide!"), King Arthur orders Bors to chop its head off.
Bors confidently approaches it, sword drawn, and is immediately decapitated by the rabbit biting clean through his neck, to the sound of a can opener.
Thus, they meet the Killer Rabbit of Caerbannog, and are forced to deploy the Holy Hand Grenade of Antioch.