Vorpal bunny

vorpal bunny, n. applied to any seemingly harmless, but actually quite lethal creature.
Ex: Kobolds that have magic resistance and shoot fireballs? What's next, vorpal bunnies? Also killer rabbit, killer bunny. See vorpal. [GJ1]
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Addendum: inspired by the killer bunny in Terry Gilliam & Terry Jones' 1975 classic Monty Python and the Holy Grail. [GJ1]
Addendum #2: One of my AD&D characters actually had a wand of conjuring vorpal bunnies given to him by a particularly sick and twisted DM. [GF]
Addendum #3: Also related to the phrase "That`s no ordinary rabbit!" with a similar meaning to "That`s no moon..." Ex: DM: "The orc uses a Whirlwind Attack to deal 22 damage to the lot of you." Player: "That`s no ordinary rabbit." [GJ1]