Aliens in the movies are generally portrayed as hostile and violent with a lust for invasion. From the earliest releases, Flying Saucers have swooped out of the sky while vaporizing mankind's most powerful weapons and shooting down our fastest aircraft. The Aliens themselves appeared in a variety of forms from bizarre lizard men to beings who look just like us. Of course, there have been exceptions to this where beings from other worlds have visited Earth to warn us of our own self destruction, welcome us into the "galactic community" and some aliens have just been left behind by mistake. Some have even been based upon real events.