81-year-old millionaire Jack Watson switches bodies with his 18-year-old grandson David, leading the two to experience life on opposite ends of the age spectrum. But when David, trapped in Jack's aged body, ends up in a coma, his grandfather must use his meager knowledge of the youth to prevent his family from pulling the plug.

Self-made millionaire Thornton Melon decides to get a better education and enrolls at his son Jason's college. While Jason tries to fit in with his fellow students, Thornton struggles to gain his son's respect, giving way to hilarious antics.