When animals pop up where we don't expect or want them—a squirrel in the garden, a rat in the wall, or a pigeon on the street—we respond with fear, rage, or simple annoyance. But do we really know why some creatures are considered acceptable and others are pests? Offering an impassioned defense of the animals we cannot abide, Bethany Brookshire suggests that how we classify these scrappy competitors says more about humans than it does about the animals themselves.