Billy is getting bigger and bigger every day, his parents tell him, and when he demands to know just how big he will get, the family launches into an amusing fantasy scenario in which Billy is so big he can move the clouds by blowing on them and wear a rainbow around his neck. Nancy Tafuri's uncluttered watercolor illustrations make a believable transition from reality to fantasy by first showing Billy as a giant among his toy boat, truck and houses, and then as a Gulliver of a child stepping over real trees and lakes in his imagination. (Ages 2-4)