-Both are part of an empire that spread across galaxies and conquer planets (Viltrum Empire and Irken Empire)-Both have been sent to Earth for their empire to conquer it-Both deal with a human with high intelligence that know what they really are (Cecil and Dib)

It’s pretty funny if you really think about it.

Also, imagine the interaction between them if they met and found they were both sent to the same planet to conquer it. Lol.

Nolan: "You don’t seem to understand… Earth isn’t yours to conquer."Zim: “You lie! YOU LIEEEE!!”