Addressing children's curiosity about animals that live in the zoo without being part of it, Ashabranner tells how Burl the Squirrel asks what the zoo animals have that he doesn't. Panda says she's cute; Peacock mentions his beautiful tail; Gorilla ruefully admits that, though he's really shy and gentle, ""You have to frighten people."" But when Burl moves into an empty cage and gets locked in, he discovers the true difference: zoo animals can't get out. Stevens' popular, comic style is appropriate to the story; her expressive animals look as though they can speak, as in fact they do. In a couple of scenes, the enclosures for some of the fiercer animals look disconcertingly inadequate, but that's a minor flaw in an unusual, entertaining story.