Irken

The Irkens are a race of typically short-statured sapients indigenous to the planet Irk.

While they appear to be superficially similar to what could be described as "bipedal insects", their true evolutionary history is not known.

Physiology and Biology
Irken brains look exactly like human brains as seen at the end of the episode Bad, Bad Rubber Piggy. It can control the PAK through 2 neural uplinks through the host's spinal cord. Unlike normal brains, it cannot function normally on its own without the PAK. Should the PAK be disconnected for long periods of time (precisely 10 minutes), the Irken's brain slowly deteriorates losing all memories, experiences and their personality until the brain completely shuts down.

An Irken's heart serves the same purpose as a human heart: it circulates blood to the cells of the body via veins and arteries.

An Irken's blood has rarely been seen in the show except for some hints on some episode like Planet Jackers when he tried to distract them by fighting them hand-to-hand. After a while we see Zim again, but this time is badly injured and his face is covered with patches of green liquid; presumably blood. This blood has a high viscosity and forms the "skeleton" of an Irken.

The Squeedly Spooch is a large super organ that seems to fill an Irken's entire torso. It seems to make up most of the Irken's rarely used digestive system.

An Irken's skeletal system is almost similar in structure as a human skeleton, but more flexible, durable and can regenerate much faster.

An Irken's teeth are slightly pink in hue and are all interconnected in rows to form one long tooth.

Irken tongues are segmented and resemble an earthworm and can extend to unknown lengths. In the episode Door to Door, we see Zim in an unnamed guy's point of view lick the lens of the holographic helmet that was unwillingly attached to his head. In the same episode we see Zim's tongue being pulled by a baby.

Irkens have smooth green skin that secretes a substance that kills parasites such as lice. They also sweat like humans and get zits (when the skin is scrubbed by an oily substance like cheese and bacon, like the bacon soap that GIR brought Zim), which, unlike human zits, can grow to enormous size (as big as a classroom when fully swollen), translucent and filled with a vast amount of pus. Irken zits also have hypnotic powers when shaken. It may be just an allergic reactions to certain chemicals such as a combination of cheese, bacon, and Acne Blast. See Diet for information on Irken skin.

The 2 antennae they sport are used to express emotion, rising up and down depending on how that Irken feels; almost a human equivalent of the eyebrows. At the Great Assigning, the Irkens salute the Tallest by wiggling their antennae, indicating that they should rejoice; similar to clapping hands. Their antennae may also serve other functions, such as smell and hearing, but it has not been confirmed. A female Irken's antennae are curled up unlike a male's bent down ones.

Although Irkens don't have any nostrils, they smell from the same area as humans; however, this reaction may be for comedic purposes for the show only.

Irken eyes come in variety of colors like red, light blue, maroon, purple, pink, and green. Maroon eyes are the most common. Irken eyes have a shine that disappears whenever they: die, become unconscious, or become stupid. Irkens have surgically installed ocular implants that enhance their eyes' 'line of sight' (but this may not apply to all Irkens), such as in the episode Walk of Doom, when Zim searches for his home base on top of a skyscraper in the middle of a city. Unlike male Irkens, female Irkens have eye lashes on both the outer sides of their eyes.

Every Irken has a PAK, which is surgically attached to their spines at birth. PAKs are vital for an Irken's life; if the PAK is removed, the Irken's 10 minute life clock starts its count down. Over the course of the 10 minutes, the Irken's intelligence, memories, personality and life force will slowly begin to diminish until the Irken finally dies when the count down ends. The separated PAK will latch onto a new host if given the chance, like what happened to Dib in the unfinished episode Ten Minutes to Doom when Dib held Zims PAK on his chest, unaware that it was attaching itself to him. The PAK contains its host's Memory Drive, an Atmospheric Processor (which converts any air into breathable air) and a Charging Cell (which acts as a battery for both the PAK and it's host). Their personality is also housed in the PAK, so that, if the PAK finds a new host, the old personality will slowly begin to replace the personality of it's new host. In the incomplete episode Ten Minutes to Doom, Zim's PAK gets disconnected. The occupation of each Irken is programmed into their PAK; any change in jobs is done by re-encoding it via a control brain. Theoretically, re-encoding it may alter its host's mind to suit his/her new job.

Life and Reproduction
Irkens are devoid of sexual organs, as we see in the episode Parent Teacher Night when Zim flash-backed to the day he was born. The most popular theory regarding this is that the Irkens use a mass test-tube method, deemung natural reproduction obsolete. In that manner the Irkens need not worry about overpopulation and unexpected births. Other theories state that the Irken race started in a collision of molecules that formed a cell obsessed with destroying other alien races. Then, the cell grew into a full Irken, and viola! the Irken race began!

Technically, Irkens do not have parents. They are manufactured in birthing facilities and are genetically engineered to suit their predestined purpose. Due to genetic shuffling, Irkens are born with different appearances and personalities to prevent the spread of a common illness just like normal development. When fully developed (indicated by a green smile on top of the capsule), the capsule which they developed in is removed and cracks open like an egg, then drops on the floor. With the sweet smeet (Irken baby) still unconscious, a robotic arm surgically attaches 2 PAK plugs and the PAK itself on its back. Another arm electrocutes it for a second, activating both the PAK and the smeet.

Once awake, the smeet is thrown/dropped into a chute that leads to another room, where a cable plugs itself into the smeet's PAK and transfers the Irken knowledge into its hard drive. This seems to be an efficient equivalent of teaching. After the transfer is complete, the smeet is put to another chute where a robotic arm puts a visor to his/her eyes and begins the virtual training that will last for 10 years (whether it be Irk years or Earth years is unknown, but it is likely Irken years).

An average Irken will grow to approximately the size of a human child. Other Irkens grow fat and wide (like Skoodge and Sizz Lor), or have a large head like Spleen, Larb, and Grappa. Apparently, some Irken can grow thin and tall (like Red and Purple). Some grow to be very short and develop a round head like Bob (Nicknamed by Tallest Purple as Bobby); however, this may be due to genetic engineering because of their height-based society. This would prevent any Irken to grow taller than the current tallest/s. When the reigning Tallest/s die, they search for another Irken second to height to the previous one and promote him/her as Tallest, regardless of social status. In the case where there are two Irken of the same height, they both become Tallest like the current Tallests, Red and Purple.

Irken diet seems to consist of factory manufactured foods, otherwise known as snacks/junk foods. Some Earth foods and drinks cause pain to Irkens. Earth water (H2O) (and some products that consist mainly of water) can burn their skin. Earth meats also have negative effects on Irken skin. On contact, the meat slowly begins to fuse to their skin, inflicting pain and agony in the process. Even their immune system can't handle meat. In the episode Bolognius Maximus, Zim becomes infected with a "Bologna Virus" that he invents in order to turn Dib into a bologna. His plan backfires, however, and Dib infects him with the virus as well. He examines his body by collecting a sample from himself, and finds out that it fuses with his body much faster than Dib's.

Irkens do not need to sleep as stated in Roboparents Gone Wild. Although, they are able to, as seen in the Pilot and a few episodes. It can be assumed that this is the reason why we never see a bed inside Zim's house.

Irken bodies also have a much faster healing rate than any Earth creature. A minor wound will heal in seconds, and a severe wound may take several hours to heal. Dismembered body parts can be easily reattached to its original position in no time at all.

When an Irken dies, it's body naturally decomposes, it's PAK is recovered (if possible), and all the data contained is transferred to the Data library located somewhere on Irk. It transfers all information about its former host; history, experiences, personality, medical records and DNA. Basically, the very essence of it's host is transferred, where it will be used by other Irken, as well as the next generation as part of the Irken Knowledge. Defective PAKs can not contribute, and are rejected by the control brain.

Culture
The Irken Empire is the militaristic governing force that rules their species. Like Saiyans, they send solitary Irkens to take over planets in the name of galactic conquest. Likely due to their naturally short statures, they place height above anything else, with the tallest of their species at any given time ruling the government, no matter how incompetent they might actually be. These officials are given the not-so-original title of "almighty tallest".

Irkens never get to know their parents. Instead, they are incubated in special machines until birth and at that point a multi-use robotic backpack is strapped to them, which it seems is never removed. Once sent on a mission, they are issued SIRs, robots that operate as vicious and deadly assistants, with one exception: GIR (who was intended as a prank SIR by the currently-ruling Tallests. Irkens are typically sent on missions all at once in an event known as the Great Assigning. It is here that the elite soldiers of the Irken Empire are chosen to become invaders - special soldiers whose mission it is to first blend in with the indigenous life on a planet, collect intelligence on the populace, and prepare the planet for conquest by the armadas.

Notable Irkens
Zim; skoge; tak;  tenn;  bob;  tallest red;  tallest purpal;  and sizz lorr;.

Trivia

 * Earth is considered on the fringe of the Irken's known universe, but has already been inhabited by Irkens like Gaz and Pr. Membrane.