Planet Sheen is the intergalactic tale of Sheen Guevera Estevez, the hyperactive and attention span-challenged kid from Retroville, who finds himself on a planet a million light-years from Earth. After accidentally 'borrowing' a rocket from his friend Jimmy Neutron, Sheen crash lands on Zeenu, a world of limited technology filled with strange-looking not-too-bright creatures, and ruled by an Emperor who is instantly fascinated by this new 'brilliant alien that built his own flying machine'.

As Earth's least qualified ambassador, Sheen makes it his mission to teach this planet the superior ways of our world, even though he has no clue what they are. This is easier said that done for Sheen, as he frequently find himself in a series of misguided adventures, as he deals with the bizarre customs and strange creatures of Zeenu, including a jealous villain, Dorkus, who wants to eliminate him, a 10-ft-tall, 2 headed princess (one of whose heads has a total crush on him), and a NASA-trained, talking chimp, Nesmith, who joins with Sheen in their ultimate quest to return home.

Of course until Nesmith and Sheen repair the rocket, there is plenty of fun to be had as our hero lives out his ultimate fantasy of being a cool, intergalactic (and hopelessly dim-witted) space warrior guy!