no don't look at me

antennae are modified "scales", sort of like the ridges/frills on earth reptiles, but more specialized

sensory pits behind eyes, similar in function to those in pythons

no body hair whatsoever

sorry not sorry for bringing homestuck into this but irken antennae diversity is slightly less varied than troll horn diversity - some variation but nothing over the top

no nipples (not mammals)

no bellybutton (not mammals; cloned)

skin is leathery and dry, retains larger scale patches on outside of joints (elbows, knees, shoulders, etc.)

"teeth" closer to turtle beaks, tongue resembles frogs', but without specialized function

3 fingers + thumb ending in keratinous points, no nails/claws; 3 toes + dewclaw

vestigial genital slit; no external genitals, no sexual dimorphism (like those lizards that reproduce entirely via parthenogenesis)

if ur interested in more in-depth junk headcanons check out this tag

cloning process resembles artificial mother grub

no need for specific "genetic material" - saliva will do 

gametes simply manufactured and randomized

empire cloning regimens render all citizens sterile, and are developing ways to reduce/remove arousal stimuli

propaganda has stigmatized natural breeding to the point that the vast majority of irkens don't even know it was ever a thing for them

this hasn't stopped physical intimacy obviously, just none of it is sexual - antennae petting is common among particularly close individuals, as is (literally) sleeping together

a common gesture of physical affection is gentle headbutts, like what cats do; they dont do kissing so much

pair-bonding isn't really a thing, or at least not the human concept of it; close irken relationships are more analogous to "families" - words used for such relationships translate closely to our familial words 

social gender has largely fallen out of use due to lack of sexual dimorphism - generally ascribed only to control brains/other archaic castes

when they DID have gender it was ternary not binary, and linked to social role

caste system is significantly more important

longer eyelashes/curly antennae are incidental traits, not linked to gender (like eye color in humans)

body mods are uncommon due to imperial influence/military culture; tattoos are not unheard of, but piercings are actively discouraged

pak system originally developed as life support when empire first began to branch out into space

now (as described in 10 minutes to doom) serves more to house personality/data - similar to cortical stacks in eclipse phase, but less refined

memories/etc. are created organically but stored digitally

countdown as seen in 10 minutes to doom occurs only in the event of forced dislodge - maintenance is preceded by safety routines that allow irkens to function pakless without time limit 

this is a security function, since they're pretty much constantly at war with people who'd like to get all their secrets

control brains came about as a way for a bunch of ancient leaders to live and rule indefinitely - instead of actually stepping down they just uploaded their brains into robots and became the shadow government

this may have also been what started the whole pak thing, as a way to deflect from the true purpose

heres a thing on what their off-world bases might be like