Aliens tend to fall into two distinct camps: those who want to zap us with lasers, and those who want to be our cool new intergalactic BFFs.
While the world-invasion types tend to grab the headlines with stunts like demolishing popular tourist destinations ("Independence Day") and vaporising the populace with death rays ("Mars Attacks!", "War of the Worlds"), the friendly aliens who come in peace are more likely to embrace humanity for all its flaws. Indeed, the 13 extra-terrestrials below have almost invariably left the world better than they found it, whether it's by saving the day, being an entertaining house guest, or expanding the fundamental limits of human consciousness.
