Irken PAK

"An Irken PAK. Irkens like Zim, Zir and Tak always use that for intelligence, weaponry, and everything else. It is essential for Irkens, because an Irken PAK is for the blood of Irkens. A beating heart for them. They're used to give Irkens life also. If they need it, then they will live longer and strong. Without it, they would die after ten minutes, if they don't wear their PAKs soon."

--Su Ji-Hoon, Coming in Peace

An Irken PAK is a backpack-like device that is grafted to the spine of every Irken upon their hatching. Serving as a secondary brain, the PAK contains all of an Irken's personality and statistics. It is never revealed what PAK stands for, or if it stands for anything at all other than a variation on "pack."