This is my head canon on irken races.
I mostly use this to identify breeds in the slave trade. (I don't care if it's illegal on you're planet, if you ever had egg adoptions you're a slave trader too so )
I might make more of these things to help fellow breeders, adopters and trainers.

Most irken oc's by the way are either of the Ploot or Teska breed. But most on the show are Muts.
Famous pure breed Invaders (Zim is a mut, but I'm still thinking of what he might be. I think he's either a mix between a Ploot's & Bobbin or a Ploot's and Teska)

Bobbin - B0b, Skoodge, Squood, Nen
Gerap - Garpa, Chin, Spleen
Ploot - Kim, Tak, Tenn, Zee, Skoo
Sante- Sneakyonfoota, Slant, Tim, Skutch, Lardnar
Teska - Tallest Red & Purple, Most Irken Guards,

(Not mine but here's the pictures)
fs71/i/201…
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Some side notes -
Bobbins are usually the most cute so they are higher in prices. Geraps are higher priced due to their rareness like wise with the Sante group. Ploot's are very common so are not as high priced. Teska's are practically given away. (Due to trader regulations it is law to advise all costumers to not adopt a Teska due to their aggressive behavior)

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These are the 5 pure breeds of Irkens or races. This sheet plays an important part to irken breeding and the selection of what breed is right for you. (Caution every irken is its own and sometimes they may not follow all breed standards. Also Irkens are highly intelligent and should be train by a professional.)

Bobbin's $$$$$
These are the shortest breed of Irkens available. Bobbins or extremely timid and easily trainable even by a beginner breeder.
-Pure Breed Traits-
Sometimes donned with freckles
Shortest of the breeds
More Circular eyes
*Health Problems*
Flaky Skin due to dryness (can be fixed with special moisturizers)
Some hearing problems

Gerap's $$$
These are Mid – Tall range Irkens and are a rare breed. Gerap's are often smug and recommended to be trained earlier in life.
-Pure Breed Traits-
Elongated Heads and bodies
Oval eyes
*Health Problems*
Prone to Slight Spinal problems

Ploot's $
These are Mid-range Irkens and are most common breed. Ploot's need to be trained early in life and can be a hand full at times.
-Pure Breed Traits-
Oval – Circular eyes
*Health Problems* (The most healthy of breeds)
More sensitive to touch

Sante's $$
These are Mid – Short range Irkens are one of the rare breeds. Sante's are the laziest breed and are easily trained if done right.
-Pure Breed Traits-
Heavily Slanted heads
Circular eyes
*Health Problems*
Prone to jaw Deficiencies

Teska's $ (Highly unrecommended)
These are the tallest of the breeds. Teska's are very hard to train even at an early age. They are not recommended for ownership as they can be a danger due to their aggression.
-Pure Breed Traits-
Longer Antenna
Oval – Circular eyes
Elongated torso
*Health Problems*
Very Prone to Spinal Deficiencies

Mut breeds are common and most often healthier but tend to be more unpredictable when it comes to training.