DOGS DON'T WEAR SNEAKERS

``...And pigs don't wear hats/And dresses look silly/On Siamese cats,'' begins this cheerful litany, by the author of If You Give a Mouse a Cookie (1985), of ridiculous impossibilities- -the last few seen from a different perspective after Numeroff suggests, ``Now just close your eyes/And draw with your mind...tell me what you see? It's your dream—not mine!'' Using soft pencil and watercolor against a white ground that dramatizes the lively activity, Mathieu, a frequent illustrator of Sesame Street books, visualizes such unlikely scenes as skunks on scooters, a skiing yak taking a header, or gnus building a ``gnu'' house in a spirited, comical style that's sure to appeal to the preschool crowd as much as the deliciously silly text does. (Picture book. 4-7)