Sent to Earth by the Almighty Tallest to conquer and destroy. He is "assisted" by his robot slave GIR and is annoyed by the earth boy Dib. Zim is unnecessarily loud all the time, but is extremely funny in his ever-failing attempts to destroy all human life.
Zim-"MY TALLEST! MY TALLEST! MY TALLEST!(repeated repeatedly)"
Almighty Tallest Red-"I was curious to see when you would shut up on your own. But it's been THREE hours, Zim! THREE HOURS!!!"