Zim is the title and main character from Jhonen Vasquez's show Invader Zim. Zim is voiced by Richard Horvitz. (However, he is voiced by Billy West in the Pilot episode) Zim is an alien-life form from the planet Irk (whose inhabitants are called Irken) and was sent by his Tallest on a fake mission to earth to be rid of him in Operation: Impending Doom II, so he doesn't mess it up like he did the first mission. The viewer knows that Zim is an alien, but in Zim's world, Dib and Gaz are the only ones to know Zim is an alien.