EJT444
This is an invader Zim story.
When the tallest were assassinated, the Irken empire finds the next in line tallest irken, which due to a typo by an unpaid intern, seems to be...Zim?
Zim's PAK is modified so he is taller, and he leaves Earth for good.
5 years later, he comes back to bug a certain Dib Membrane.