Smeet is the term commonly used for Irken babies.
Despite most modern smeets being born far beneath Irk's surface in artificial chambers, it is likely that the smeet in general has not changed for a very long time. Essentially an Irken baby or child, there is little to really describe about the smeet itself.
Modern Smeets - Birthing
In the 'modern' times of the Irken Empire, the average Irken smeet is actually cloned from a presumably random sequence of genes. Mixed together typically within wall-mounted vats or capsules deep beneath the surface of Irk, an Embryo is created from the genes. Within the capsules, the Irken Smeet gestates and grows for an unknown amount of time within an unknown, likely life-sustaining green fluid.
Once the Irken smeet is fully developed, the end of the standard gestation capsule, displaying a presumably holographic face, will change said face to a green smiley. Mechanical arms, presumably controlled by a control brain, swing in, with one unscrewing the capsule as steam hisses from the previously-occupied chamber, and pulls it over with it's sibling arm to a space above the floor.
On one side of the capsule is a metal section with a joint about half-way, a component likely developed to allow the capsule's re-use following the somewhat violent birth. Said birth consists of the two arms flexing towards the 'quick-break' joint, with the glass shattering, and the contents within spilling (and flopping, in the case of the smeet) out.
Immediately after it lands, presumably unharmed, the smeet is immediately given a PAK, and is greeted with a robotic voice, saying, "Welcome to Life, Irken Child." The greeting is immediately followed up by "Report for Duty." It is notable that the Smeet is immediately able after that to stand, speak, and walk, and some (such as Zim) even declare an affection for the 'cold, unfeeling robot arm'.
Immediately after, the Smeet is delivered to a chamber where it is given the supposed whole of Irken knowledge.
Notably, Zim complains in his Existance Evaluation Trial that he wasn't given enough Irken knowledge and claims that there was 40 shmillion mistakes during his PAK transfer, which may be why he is a defective. Notably, Zim also once pushed another smeet into the chute leading to his download chamber, jamming the chute and plunging Irk into a blackout known as Horrible Painful Overload Day, later known simply as the first part.
Soon after, for a ten year period (unclear if this is Irken or Human years) most, if not all spend their childhood dwelling under the surface of Irk, being trained in combat and warfare tactics. After this decade is up they are considered full Irkens, and are given jobs and ranks via encoding to match his/her abilities and talents. Most importantly, their individual height is able to predetermine their class distinction in the Irken Imperial Society.
It is unknown how Irkens were born before the cloning technology came into use.Some theorize that due to the Irken race's insectoid characteristics and similarities they may have been born via Queens and eggs, just like ants.