The alien invasion is a typical part of both science fiction stories and film, where evil extraterrestrials invade Earth either to exterminate or take over the position of human life, enslave it under a system of colonialism, harvest humans for food, abduct them, use them for human test subjects, infect them, terrorize them, possess them, remove their brains, declare war, start riots, wreak havoc, cause anarchy, escalate rebellions, promote civil unrest, escape with the earth's resources, or simply just destroy it completely.