Kreton (Jerry Lewis), an impish creature from outer space, has an insatiable curiosity about humans and their ways. When he journeys to Earth and parks his spaceship in the backyard of Conrad (Earl Holliman), a skeptic who doesn't believe in aliens, both are in for big surprises. This classic sci-fi comedy is based on the successful 1957 Broadway play by Gore Vidal, who initially disagreed with the casting of Lewis in the lead role for the film.