*Zim is banished from the Irken Empire after almost destroying his home planet on a previous mission. When he begs his superiors for another chance, they trick him into going on a "secret mission" to Earth, a planet they believe is of little interest. Zim arrives safely on Earth and disguises himself as a human child, but Dib sees through his disguise and makes it his mission to defend the planet from Zim. The series follows Zim and his adventures as he tries to take over the planet, while Dib tries to expose him as an alien. However, most of humanity is gullible and ignorant, and usually thinks Dib is crazy. *