Zim (voiced by Richard Steven Horvitz, Billy West in the pilot and Melissa Fahn as a newborn in his flashback of "Parent-Teacher Night") is an incompetent Irken who is arrogant, foul-tempered, reckless, overzealous, uppity, impatient, impulsive, naive, megalomaniacal and convinced of his own greatness. He dreams of regaining his leaders' trust by taking part in "Operation Impending Doom II", so Zim is assigned as an “invader” to Earth, a planet which the Almighty Tallest believe has little to no chance of existing. However, against all odds, Zim makes it to Earth and establishes a base on a fake conquest mission. Zim disguises himself as a human child using a hairpiece to cover his antennae and contact lenses to make his eyes look normal.