The main character is an American astronaut Captain Charles "Chuck" Baker. He lands on Planet 51, which at first seemed to him to be deserted. To his surprise, he discovers that the planet is inhabited by little green men. Their community is very much like a happy one-story America of the 1950s. And these men are only afraid of the attack from alien invaders, such as Chuck! Relying on the help of his robot companion "Rover" and a new friend Lem, Chuck will have to go around this entire marvelous and strange world, not to become a permanent exhibit at the Museum of the Planet 51 Alien Invaders.