Everything in Mrs. Potter's house is cleaned to a fare-thee- well except her messy little baby, Ermajean. Ermajean drools and gurgles and plasters herself with applesauce, and ``any speck of dirt in the yard clung to Ermajean like bees to clover.'' Ermajean is so dirty her mother worries she'll turn into a pig. When she finds a little porker in Ermajean's stroller she thinks the worst has happened, until she discovers Ermajean happily splashing it up in the pigpen, ready to introduce her mother to the joys of mud. Root (see review, above) has written a very funny story of mistaken identity. Readers see Ermajean and the piglet switch places while Mrs. Potter dusts the picket fence. Ayto's loose line and watercolor illustrations are a perfect complement for the rollicking text, imbuing every character with lots of personality. The scenes of Mrs. Potter in the mud are priceless, and the piglet is particularly endearing. (Picture book. 4-7)