Josh Baskin is a 12-year-old boy who, like many kids his age, feels frustrated by the limitations of being a child. One day, at an amusement park, he makes a wish on a mysterious machine to be "big." When he wakes up, he finds himself in the body of a 30-year-old adult (played by Tom Hanks), giving him the chance to experience the world from a new perspective. Although he initially enjoys the freedoms of adult life—from having a job to partying—he soon realizes that being big also comes with responsibilities and complications he never imagined.
Josh lands a job at a toy company, where his childlike enthusiasm and unique perspective lead to unexpected successes. Along the way, he forms a heartwarming friendship with his boss, Susan, who is attracted to him, unaware that he is actually a child trapped in an adult's body. As Josh navigates the ups and downs of the adult world, he is forced to confront the inevitable reality of his wish and the need to return to his childhood.
With a comedic tone and moments of deep reflection, the film explores the loss of innocence and the search for true happiness, reminding us that while growing up can be exciting, there’s nothing like the purity and joy of childhood.