At a carnival, young Josh Baskin (Hanks) wishes he was big - only to awake the next morning and discover he is! With the help of his friend Billy (Jared Rushton), Josh lands a job at a toy company. There, his inner wisdom enables him to successfully predict what children want to buy, making the awestruck, naïve Josh irresistible to a beautiful ladder-climbing colleague (Elizabeth Perkins). But the more he experiences being an adult, the more Josh longs for the simple joys of childhood.