Description from original post (created 2012-06-25 09:43):
Zim is voiced by Richard Steven Horvitz[1] in the series and Billy West in the pilot. He is an incompetent Irken invader who is overzealous, impulsive, and convinced of his own greatness and dreams of regaining his leaders' trust by taking part in Operation Impending Doom II (his own incompetence led to the failure of Operation Impending Doom I), the Irkens plot to conquer the universe and enslave all races. He is assigned 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 mission of conquest. Because of his very small stature, Zim disguises himself as a human child using a hairpiece to cover his antennae and contact lenses to make his eyes look normal.
Despite his tendency to vociferously malign humans as a species, constantly shouting at everyone that they "LIE!" whenever things do not go his way, his undisguised green skin, a severe allergy to baloney and water, his refusal to eat human food, multiple failures in his disguise, and an occasionally blatant disregard for his own cover, no one realizes that Zim is an alien, except Dib and Gaz although the other children in his class say that he's a little weird. Zim has no friends, and physically harms other kids when they attempt to befriend him, they will always defend him when Dib calls him an alien. He is equipped with a PAK, a backpack-like piece of equipment with (among other gadgets) long, retractable arms that enable him to move about quickly and climb almost any obstacle. Zim also has a very unique way of getting around by using several of these mechanical arms that come out of his PAK when he needs to get around really fast. When moving with these extra arms he moves more like a spider. Zim constantly schemes to enslave or destroy mankind, and despite his access to potent Irken technology, his plans, frequently based on misconceptions, are never successful. He serves as the main protagonist of the series, but is sometimes depicted as the antagonist when facing off against his rival Dib. He usually goes over the top with his various and ridiculous plans and they all end blowing up in his face, often quite literally, such as in the episodes "Walk for your lives", "Zim Eats Waffles" and "GIR Goes Crazy and Stuff". According to the episode Germs, Zim has a very strong fear of germs and goes nuts trying to keep his home (base) clean of them. Zim also has a high tendency to call and to think of himself as a being who's amazing or ingenious and will sometimes refer to himself in third person when he is acting very prideful and excited. When feeling like so, he strongly hates being questioned by someone of a lower ranking order than him like GIR or Dib. For the most part Zim mostly interacts with Gir, Dib, Ms. Bitters and once in a rare while Dib's younger sister Gaz. However, he also has to a lesser extent some interaction with lesser known characters like Keef, Tak (who's another Irken, but an enemy of Zim's) or in one instance Dib and Gaz's dad Professor Membrane. In The Frycook That Came From All That Space, it is shown that Zim has the ability to remember what other characters say or do even when he is not there. He doesn't know how or why he has this ability, he just does and it's never talked about in the rest of the episode or the series. In the episode "Lice", it is revealed that Zim's skin kills lice. Zim's favorite sayings are "You lie!","I am Zim!" and" You, obey the fist!" He also laughs very loudly and maniacally when feeling like his ingenious plan is going to work, at his peers misfortunes or when he's torturing someone -which would most likely be Dib and very rarely ever Gaz