|Voiced by||Richard Steven Horvitz|
Zim is a member of the alien Irken race. As Zim is severely emotionally unstable, he is considered defective. Zim, on the other hand, believes that he is a mighty warrior. Since his actions usually lead to disaster (he nearly destroyed the Irken homeworld during Operation Impending Doom I) his leaders, the Almighty Tallest, sent him to Foodcourtia as a sort of exile. While there, however, Zim heard about Operation Impending Doom II, and (obviously not understanding the purpose of his previous exile) returned to Conventia in the hopes of getting an assignment. Chagrined, the Almighty Tallest sent him on a "secret mission" to Earth, in order to keep him away from Operation Impending Doom II.
After arriving on Earth, he enrolls in the nearest elementary school to begin his infiltration and quickly becomes rivals with Dib, an avid preteen paranormal investigator. Zim wants to conquer the Earth, mostly to prove his superiority and impress his leaders.
Although he is the protagonist of a children's show, Zim is, morally and ethically, a villain (though occasionally considered an antihero), being overall a fairly unsympathetic character and usually only causing chaos and destruction for either himself, his own race or Earth.
At first, Zim did not care about Fuse's invasion of Earth, but as Earth became more infected, Zim decided to join the fight against Fuse, believing that the invasion is a threat to his own conquest of Earth.
He and GIR are not getting along and the two separate. Zim ends up at the Castle of Evil, though he was kicked out because he was not "impure" enough. He landed into a middle of a battle in Champion's Paradise.
Zim is also working on how to hack into Fusion GIR in Fuse's lab to put its parts into the actual GIR.
Zim is the main reason why all universes have all run together. His time machine was supposed to send Zim back in time so he could have killed Dib, but soon the FBI found proof of Zim's "heritage" and staged a raid in his home. They thought that the time machine was a torture device and tried to destroy it while the time machine was creating a portal. This caused it to malfunction, causing a temporal rift and in another dimension an Elder Scroll reacted to the time paradox, thus pulling all universes together.
Leveling A House
In this Nano mission, Zim asks the player to go to his town to retrieve the blueprint for a device that he once made to boost GIR's intelligence. When the player retrieves the blueprint from the Skool Infected Zone, Dib asks the player to the player to give it to him, requesting the player to leave it on his mustache gnome. He wants to compares it to the junk in GIR's head, since he doesn't believe Zim's explanation.
Just then, a message comes from Dexter to come to Dexlabs immediately. Dexter has discovered that a Fusion has been looking for an item in Zim's town and destroying houses to find it. Meanwhile, Dib calls to inform the player that Fusion Zim has stolen the blueprint for the "intelligence boosting device."
When the player interrogates Zim about this, he panics and confesses that the blueprint is actually for a cloning device filled with Fusion Matter, which can be used only by a robotic Fusion and will explode if it goes too far away. The only possible explanation is that Fusion Zim is making an army of Fusion GIRs by giving the Fusion GIR the ability to clone itself.
The hero races to the Fusion lair in Zim's old house and discovers Fusion Zim has just installed the device into a Fusion GIR. The hero battles Fusion Zim first, and receives a Zim Nano; then he must battle Fusion GIR to retrieve the cloning device and exit the lair.
- Ironically, Zim is the closest thing Dib has to a friend.
- Jhonen Vasquez has stated that the four main characters of Invader Zim aren't evil and that Zim and Dib are both "good guys" but on "different sides". This makes sense in Zim's case, as he is a "defective" and can't tell the difference between right and wrong.