Any kid who's visited a public place on a crowded day will embrace this paper-over-board book's driving joke. As a humongous, potentially bladder-busting-long line stretches out from the front door of the zoo's apparently single public bathroom, two kids speculate about who is inside. ""Is it a tiger who needed to tiddle?/ A wandering wombat who wanted to widdle?/ A waddling penguin too frozen to piddle?"" Willis (Susan Laughs) and Reynolds (illustrator of the Harry and the Dinosaurs books) clearly had a great time dreaming up the likely suspects, which range from a primping leopard to a flatulent rhino. But while they readily indulge readers' taste for toilet humor (even grownups will smile at the poor penguin's fluid frozen in mid-stream), the rhymes' chipper, efficient tone and the pictures' bright colors and crisp lines provide a sense of restraint and propriety that's deeply reassuring, especially to the newly toilet trained. As for the answer to the title: why, it's an octopus, who's dutifully ""doing what my mom told me to do""-after going to the bathroom, he's washing all of his ""eight little hands."" Ages 3-8.