This is a list of characters from the animated Nickelodeon TV series Invader Zim. The recurring cast includes long-term Nickelodeon voice actors Richard Steven Horvitz and Rodger Bumpass, as well as actors from live-action television such as Kevin McDonald (Kids in the Hall) and John de Lancie (Star Trek: The Next Generation). The creator and writer of Invader Zim, Jhonen Vasquez, also voices parts in the show.
- Voiced by: Richard Steven Horvitz, Billy West and Mark Hamill (pilot), Melissa Fahn (meep), Naomi Nagasawa (Japanese dub)
The titular protagonist. Overzealous, impulsive, and convinced of his own greatness, Zim is incompetent as an invader. He dreams of pleasing his species' leaders the Almighty Tallest, by taking part in Operation Impending Doom II, which is an Irken military initiative to conquer the universe. The Tallest send him to Earth (a planet of no interest to the Empire on the outskirts of the known universe) on a fake mission of conquest. They were expecting him to die or become lost on route. Against the odds, Zim lands on Earth, establishes a base and, much to the chagrin of the Tallest, routine communication with his home world. Because of his stature, Zim disguises himself as a human child using a wig to cover his antennae and lenses to make his eyes look normal. Despite his tendency to vociferously malign humans as a species, his undisguised green skin, a severe allergy to polluted 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—with the exception of Dib and Gaz. In spite of his slight build, Zim occasionally displays superhuman strength and agility, although due to the show's lack of continuity, these traits are not always present. He is never without his PAK, a backpack-like piece of equipment with long, retractable arms that enable him to move about quickly and climb almost any obstacle. 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.
- Voiced by: Rosearik Rikki Simons, Wasabi Mizuta (Japanese dub)
The deuteragonist. Zim's only companion, GIR, is a SIR (Standard Information Retrieval) unit, an Irken standard-issue robot. He is completely made of different parts from SIR units found in a trash can. The name "GIR" is a self-applied moniker that is never explained, GIR himself states that he doesn't know why he refers to himself as GIR, ("GIR, reporting for duty." Zim: "'GIR?' What does the G stand for?" GIR: "I don't know!") but it is insinuated in the show the G stands for garbage. GIR differs physically from other SIR units in that his head contains odds-and-ends rather than artificial intelligence hardware. Because of this GIR displays a wildly erratic personality. He is almost completely irreverent, and rarely obeys Zim's commands, variously due to distraction, disinterest and disobedience, but when he does, his eyes glow red like normal SIR's and he will usually refer to Zim as "My Lord" or sometimes "My Master", but in the episode, "Gir Goes Crazy and Stuff," Zim actually tries to improve Gir's obedience skills but it ends up backfiring when Gir sees him as an enemy. GIR disguises himself by wearing a green dog suit which fools most humans, despite looking and acting almost nothing like an Earth dog. He also does things that a real dog wouldn't do, such as talking in public, dancing and using jet rockets. His head is a thermos, and you can see that in Bad, Bad Rubber Piggy, an episode in the first season. Also, GIR loves tacos, and is also hyper because of the fact that he lacks an artificial intelligence in his head.
Voiced by: Andy Berman, Ayumi Kida (Japanese dub)
The main antagonist. Zim's mortal enemy, Dib is highly unpopular at school (where he shares a class with Zim) and at home for his broken record obsession with the paranormal, aliens, Bigfoot, the Loch Ness Monster, and other paranormal phenomena. He and his sister, Gaz (Who couldn't care less.), are some of the only humans who know that Zim is actually an alien. He is the co-protagonist of the series, but at the same time being the antagonist because he is constantly trying to break into Zim's house, or even go as far as pushing Zim into polluted water (which is equivalent to acid to Zim's skin).
- Voiced by: Melissa Fahn, Haruhi Terada (Japanese dub)
The secondary antagonist. Dib's creepy, anti-social, and somewhat apathetic younger sister, Gaz is often described as "Dib's scary sister." She has a penchant for video games and a fixation with pizza. If and when someone or something stands in the way of her getting those things, she won't hesitate to thrust them into "a nightmare world from which there is no awakening." She knows and admits that Zim is an alien, but doesn't care because she thinks he's too stupid to take over the world. Although she is possibly the smartest character on the show, Gaz, like the others, may have shown some obvious signs of insanity. Her vengeful and explosive nature shortens all How I Met Your Mother common reasons to care about the satisfaction for others, especially that of her brother. She loves to play Game Slave 1 and 2. It is also implied that she is the smartest among the main characters. She is younger than Dib and it is implied that she and Dib have about a few months or 1 year of age difference.
The Almighty Tallest (Red and Purple)
- Voiced by: Kevin McDonald (Purple) and Wally Wingert (Red)
The true antagonists. The Irken Empire has a hierarchal class structure, where shorter individuals are both figuratively and literally looked down upon. The tallest Irken born in a specific generation takes command of the Empire as "the Tallest", but since Red and Purple, the two current Tallest, are the exact same height, they share equal (and high-supreme) power. While the Tallest function mainly as figureheads, doing little to organize the society (preferring to lounge around and eat snacks), they do hold absolute power over the populace. They travel around to observe and supervise Operation Impending Doom II. They appear to mostly use their unlimited powers of state to amuse themselves- sending loyal Irken soldiers to painful deaths ("Battle of the Planets"), forcing others weaker than themselves to obey their random whims ("Hobo 13") and starving their own command crew ("Backseat Drivers"). The Tallest also seem to enjoy puppet shows, in the episode "Walk For Your Lives", they have fun beating up those invaders who do not put on a puppet show for them. They also hate short Irken soldiers like Zim and Skoodge. They were the ones who sent Zim to his mission on earth. Little does Zim know is the fact that they only sent him there so they could get rid of him.
- Voiced by: Rodger Bumpass
The tertiary antagonist. The world's smartest man, host of the popular television show "Probing the Membrane of Science", inventor of SuperToast, and father of Dib and Gaz, Membrane's scientific abilities are offset by incredibly poor parenting: His primary method of managing his children is by way of a floating digital projection screen - and his messages to them are often not only prerecorded, but woefully out of date. Dib often goes to him for guidance and / or to show him of his findings. Even though some of Dib's evidence is sometimes very believable, Membrane always tells Dib that there is a reasonable, and scientific, explanation for anything Dib's found and he calls him "his poor insane son". And it seems that he does not have a wife and manages his children alone. It's also suggested that he was never married according to most people (though this info may be unconfirmed because the writers of the series and Jhonen Vasquez himself have not revealed about it), and Dib and perhaps Gaz as well were created through science.
- Voiced by: Lucille Bliss
Ms. Bitters is the teacher for Dib and Zim's class. She is a tall, slender, aged woman that is very creepy in many ways. True to her name, she is devoid of any compassionate emotion and having a very demonic hatred for life. Her body has a "snake-like" quality, and is animated as such that it seems she can "slither" around (and in one episode, floats), and sticks out a forked tongue while hissing. She also bears a sensitivity to the sun (Season 2, Episode 13, 15:32 - 15:37). Occasionally she emerges out of other people's shadows and even suck people into her own. The character is directly pulled from Vasquez's earlier comic book series Squee! where she was Todd's teacher.
- Voiced by: Olivia d'Abo
Tak is one of the seemingly rare female Irken invaders who has had many unfortunate encounters with Zim. One of them includes inadvertently trapping her in a building on Devastis (The Irken military training planet), therefore missing her chance to take the test to become one of the Irken Elite Soldiers (and an Invader). In the one episode that she is in (Tak: The Hideous New Girl), she tries to overtake Zim's position on Earth, but fails miserably in the end. Tak's holographic disguise (particularly the clothing) somewhat resembles Johnny from "Johnny the Homicidal Maniac", a comic by Vasquez
MiMi is a SIR unit who was built for Tak on planet Dirt. Her disguise is also holographic, and is generated as a cat.
Piggy is a rubber pig that belongs to GIR, and is thrown into the time machine in the episode "Bad, Bad Rubber Piggy." GIR:"Why my piggy,I loveded piggy,i loved yooohoooou!!"
- Voiced by: Jhonen Vasquez
Zim's computer is normally seen talking with Zim. He is scattered around the House and Base so Zim can talk to him whenever he needs to. The computer often doesn't know what some of Earth's organizations (like the FBI) do, so he guesses. This often results in completely wild explanations. For example, when Zim asks computer to explain the FBI, the computer guesses and says the FBI was founded by demons, flies, and fights with corn. The Computer also seems to display defects, similar to GIR, in both that he lacks information on Earth and will occasionally change his voice tone to a much more harsh version at usually completely unnecessary times and situations. But he can be the voice of reason to some of Zim scheme's that usually end up in flames.
- Voiced by: Jhonen Vasquez
Minimoose is the Irken empire's superweapon, but Zim doesn't know how to use him.
Minimoose is Zim's other sidekick. Zim has stated previously that Minimoose has been with him since the beginning.
- Voiced by: Ted Raimi
Skoodge is a successful competent Irken Invader, assigned to planet Blorch, home of the slaughtering rat people, due to his shortness. However, he was the first Invader to successfully conquer a planet in Operation Impending Doom II, but is prejudiced against by the Almighty Tallest, who proceed to launch him into the planet as the first shot of the destruction, but he survived. Skoodge's personality is kind and very loyal to The Almighty Tallest no matter how much they hate him. He was planned to be included in future episodes of the show, but it was canceled before the episode could be finished.
An Irken character who works at Foodcourtia in an episode. Sizz Lor comes to Earth in the episode "The Frycook What Came from All That Space". It is his only appearance.
- Voiced by: Danny Cooksey
Keef is an annoying child that attends the Skool with Zim, and his only important role was in the second episode, "Bestest Friends". In this episode Zim got rid of him by removing his eyes and putting in new, robotic ones. He then tricked Keef into thinking the first thing he saw was Zim. The first thing Keef saw was a squirrel. He was supposed to appear in an episode they made called the "Return of Keef" but the animation was never finished because the show had been canceled.
Robo parents and gnomes
Robo parents and gnomes are Zim's helpers that guard him and help make him look more human. The Robo Parents appear to be poorly built and seem to have a lack of normal parental behavior. The Robo parents constantly go insane and attack visitors to Zim's house. The gnomes protect Zim's house at times when people are in the yard, such as Dib.
The creature who wrecked Zim's Voot Cruiser in an episode. Zim also vowed to destroy that bee, but never did.