Buenos dias tardes noches
Things to explain the origin of my Oc :>
The parasite "bit" Prime when he was on some unimportant planet x for a mission or something. Since there were no side effects from the bite, which he considered insignificant due to his great faith in the Krangs' immune system, he continued with his daily life without suspecting that this little thing was growing inside him.
As it grows and develops, the parasite releases a part of itself directed toward the mind and nervous system of its host. It doesn't control his mind and is not yet "active." This doesn't affect Krang Prime's personality or health in any way, so he remains completely unaware.
The parasite managed to hide and grow silently for at least 5,000 years before either "being born abruptly" or "being born abruptly but trying to pass itself off as a real offspring."
When the parasite is born and its "host" holds it and sees it for the first time, the part of the parasite that remained dormant in the mind of... Prime, when activated or "turned on," would nullify any thoughts or natural instincts it might have that could harm the parasite. Clearly, without this, Prime would have instantly killed the parasite upon realizing it wasn't of its species.
Instead, a protective instinct so strong would come to mind that it would obviously confuse him, but he would obey without knowing why, despite knowing what he should have done. It wouldn't be instant love, although that would develop gradually over time, since the thing in his mind, besides making Prime see the parasite as something to protect, would also force him to "love" it and recognize it as his own true offspring, even if he knows that's not true, he would convince himself that it is.
The, let's call it, "root" in Krang Prime's mind wouldn't totally control him, as I said, it would simply drive him to protect the parasite, which at birth would be very defenseless (it had 5,000 years to form and is born weak xd). Most of the time he would be almost in "calm" mode, just fulfilling his duty to make Prime see the parasite as something valuable. Prime would remain the same all the time, apart from the fact that now he would take his "offspring" everywhere with him and sometimes show it affection, not caring if others judged him. (In this universe, he would be a high-ranking Krang, so it's not like everyone could complain about him)
Krangs aren't exactly known for being a loving species with their children. They're born, and the parents don't care what happens to them. With Prime, it obviously wasn't like that because of the parasite's "root" in his mind.
By keeping the parasite, Prime would constantly be asked or pressured to kill it, etc. He would always respond aggressively during the first few months because he was stressed by the constant demands to kill his "baby" or the fear that someone might try. This pressure led him to kill some unfortunate souls
And that's all I can think to explain about this Oc, and please note that I'm not very good at explaining :^