Why Evolution Is True introduced me to a profoundly awesome example of mimicry in nature: Uropyia meticulodina, a moth from eastern Asia that looks like a dead leaf.
Real Monstrosities: "It's not just brown like a dead leaf, it's brown like a curled up, dead leaf. And it's not just brown like a curled up, dead leaf, it depicts a leaf catching the light, with shadows in all the right places and you can even see the veins casting tiny shadows along the curled underside. It's like one of those optical illusions that still work even when you know it's a trick."
Here's what it looks like "normally", or at least when pinned to a board. (Hsu Hong Lin, CC)