One night Josh and his family go to the local fair and he notices his dream girl standing in line for a pretty intense ride. Trying to impress her Josh gets in line and talks big about having ridden on the ride a bunch of times. But, when he gets to the front of the line they all find out he is too short to ride the ride.
Dejected, Josh walks away and finds this strange machine called a Zoltar. The machine asks you to make a wish and if you shoot the quarter in its mouth, your wish comes true. Josh sinks the quarter - and his wish will come true. But, he notices that the machine is working without even being plugged in.
That night Josh goes to sleep as a 13-year old boy - and when he wakes up is an adult (now Hanks).
Scared out of his mind, because his mother doesn't believe it's him, Josh seeks out his best friend Billy (Jared Rushton). At first Billy doesn't believe him either, but Josh is able to convince him.
They come up with the idea to move to NYC and blend in by getting a job until they can track down the Zoltar machine so that Josh can be switched back.
The film (and Hanks) portrays Josh as a young, naive man who is trying to figure things out in the adult world. Including his first girlfriend and possible sexual experience with Susan (Elizabeth Perkins), which is both sweet and, if you think about it, creepy. Both the film and Hanks portrayed this masterfully.
Big is one of the few films about switching bodies that actually did well during the era. But, it was the lone film that wasn't about switching bodies with another person.
Since then, we have had a few ripoffs, 13 Going on 30 and 17 Again! come to mind. Neither is even close to the quality of Big, though 13 Going on 30 is decent and from a girls' point of view.
The film, despite being released in the late 80s, still pretty much holds up. Sure, the toys that Josh is helping create and plays with are of the 80s persuasion, but heck they're all coming back out again anyway - so that shouldn't stop you from enjoying it.