With 31 little mice to feed, mother mouse has to work as a roller-skating instructor and father mouse holds down three jobs--construction worker, cook, and writer. With a 32nd little one dropped on them as a doorstep baby, both begin ""cracking up."" Then the story becomes a flight of parental wish-fulfillment, with the little mice taking over the house-cleaning and the older ones getting after-school jobs to give their parents a needed vacation. When the rested parents return happily to work as a fireman and a tennis instructor, the youngsters continue their contributions. And that's it: good-natured like all this trio's collaborations, and decorated with teeming crews of busy pastel mice, but no less ephemeral than the title indicates.