Zim

Zim is the main protagonist of Invader Zim. He is voiced by Richard Steven Horvitz.

Appearance
Zim's appearance, like that of most of the Irken race, seems to be based off the typical "little green men from outer space" stereotype. Many Irkens are about the size of a preteen schoolchild, but Zim is exceptionally short. In The Nightmare Begins, Zim was shown to be even shorter than the notoriously diminutive Skoodge.

Zim also has ruby-colored eyes; a very common trait in Irkens. It was also mentioned in Walk of Doom that Zim's eyes contain ocular implants. Since the eyes he was born with are not visibly different from subsequent appearances, it can be assumed that these implants are subcutaneous. As he considers himself to still be an Invader, he continues to wear the standard uniform: a red tunic-like garment with a pink collar and sleeves, as well as black boots and gloves.

He also possesses a pair of antennae; their exact function is unknown, but they seem to function like human eyebrows; rising and lowering to convey emotion. It is possible that they also function as an organ in place of ears, as they picked up vibrations in Battle of the Planets.

Personality
While most Irkens are expected to be ruthlessly loyal to the Empire, Zim is considered overzealous even by their standards: Brash, arrogant and overconfident, Zim's tendency to cause wanton destruction makes him a danger to himself and his own people, yet he still considers himself a mighty Irken warrior. In addition, he is acutely narcissistic and megalomaniacal, congratulating himself on even the smallest of successes; these, however, are rare:

Zim putting in his best effort to learn about about human behavior and emotions, in this case the emotion of love Despite his self-proclaimed greatness, Zim rarely succeeds in his attempts, and is held up as a complete laughingstock by his own people - a fact that he is either oblivious to or simply chooses not to notice. Zim is cluelessly loyal and obedient to the Tallest, the Irken Empire, his planet and his people, and is willing to go to ridiculous lengths to please his leaders. However, his self-absorbed nature prevents him from acknowledging any of his failures, and he chooses only to speak about the better things that came from each incident.

Zim's laugh and mannerisms can be said to be somewhat derived from a masculine equivalent to the unpleasant "ojou" stereotypes common in anime and manga, and "rich person"/"popular schoolgirl"/"spoiled brat" stereotypes of Western animated cartoons and movies, combined with the "overconfident alien invader" stereotype seen in sci-fi shows and movies.

Despite his frequent displays of stupidity, it is clear that Zim is highly intelligent in some respects - being a keen manipulator of tools and devices - but has absolutely no apparent interest in thinking things through, and wastes much of his time fretting about or dealing with unimportant "threats." Moreover, it is evident that he is more than capable of conquering the Earth, yet he hardly ever uses this capability properly, and has often been very close to taking over the planet, only to be thwarted by his own negligence.

One of Zim's abilities is his somewhat inconsistent skills at piloting; while in a tense situation he flies masterfully, but seems to crash on most other occasions, and his skills pale in comparison to opponents adept at hand-eye coordination or overall agility (such as Gaz). Zim also has admirable engineering ability; in Walk of Doom, he singlehandedly improved the SIR unit guidance system chip, and in Walk for Your Lives, he hand-built a variable time stasis field capable of altering individual time-fields. He is immensely proud of anything he creates, yet is often frustrated when his devices fail to live up to his grandiose expectations.

Even though Zim often affirms that he wishes to enslave Earth, it has been hinted that he would not actually want to rule it. In Attack of the Saucer Morons, Zim gained a group of human worshippers who would be willing to do his bidding, yet his only thought was escaping them. In the non-canon Nickelodeon Magazine Special, in which Zim finally took over the world, he did not stay to rule for very long, instead leaving Earth forever to ride flying alien rabbits and drink soda.

Zim usually shows little to no affection, often claiming to "need no one", but he occasionally lets a softer side of him slip by accident. In Parent Teacher Night, when Zim thought back to when he was born, he remembered the first thing he ever said was that he loved the "cold, unfeeling robot arm" that "hatched" him from his incubation capsule and activated his PAK.

Strangely, it would seem that Zim also relies on the presence of his mortal enemy, Dib, for motivation. He said in A Room with a Moose that his mission might not be as "exciting" without Dib around to "annoy him", but also seems to dwell on the big-headed human quite a bit, sometimes more so than his actual mission. This importance was particularly highlighted in Mopiness of Doom: When Dib briefly decided to give up his pursuit of Zim, the Irken lost all motivation to take over Earth, or do anything in general.