Leaf beetles of the genus Neochlamisus are sometimes known as the warty leaf beetles. They are members of the case-bearing leaf beetle group, the Camptosomata. Measuring 3-4 millimeters in length as adults, they are cryptic, superficially resembling caterpillar frass (that means bug poopies)
From the Peterson Field Guide of Beetles:
"These beetles are easily mistaken for caterpillar droppings. Even after a collector thinks he has learned to recognize them, he can still be fooled -- occasionally in collections there are caterpillar droppings that have been mounted and labeled, right along with specimens of warty leaf beetles." WHUT?
And because it's not that huge of a WTF, I give you more insects that look like poopies