A snowy day inspires a girl's thoughts of the fun to be had if it snowed indoors as well as out—sledding down the stairs without fear of bumping a head, keeping a penguin as a pet, building snowmen in the living room and an igloo in the attic, and frozen peas that ``would sit and freeze till spring arrived once more!'' Imaginative and creative uses for a frosty interior are matched with equally frisky illustrations, which border on the bizarre: The heroine's bulging, googly eyes vie with her parents' blue lips and noses in commanding second looks. The mental merriment lasts until nighttime, when she drowsily realizes that her bed is cozy, that warm good-night hugs and kisses from parents are nice. A zany sojourn into a topsy-turvy, ``what-if'' world that comes off just right. (Picture book. 4-8)