A penker is a person that penked someone on purpose or by accident. A penker can penk someone during April Fools day as a practical joke, or a someone can be made a penker through accidentally damaging a pen. The damaged pen would then be used by another person, and that person would find themselves with ink all over their new pants.
I can't wait to see Joe's face when he gets penked...
Penk is the act in which a pen ruptures or ink is leaked and gets all over one's hands or clothing. One can also get penked by others as a practical joke or by accident. Such people are called penkers.
Aww man! My pen just exploded now I've got ink all over my brand new shirt!