This concept was apparently so good that two different publishers have used it. The illustrated Whose Bottom Is This? is a hardcover lifttheflap guessing game for children ages 1 to 3. Those same children can then graduate a few years later to Wayne Lynchs photographic series of books, which include the posed posteriors of hippos, rhinos, bighorn sheep, pintailed ducks, and more. It might be good preparation for a childs first field trip to the zoo, so long as someone teaches them what animals look like from the front as well.