Perhaps you heard earlier this week that rocker Sammy Hagar revealed he believes he has been visited by aliens.   Watching the History Channel like I do, I know all about the vast universe of alien visitation theories.  From io9, here are the top Alien Conspiracy Theories:

1-Roswell:  An alien craft crashed in the New Mexico desert in 1947 and the government has been hiding the evidence ever since.

2-Area 51:  The Big Secret Base in the Nevada wastelands north of Las Vegas.  Shoot to kill orders for anyone who breeches the perimeter, no-fly zone, and secretive comings and goings fuel the speculation here.

3-Replitlians:  The aliens are among us.  They are actually lizard-like creatures who show a human appearance.

4-Ancient Astronauts:  We have being visted for thousands of years and it was the aliens who brought life to the earth.

Go in depth with these alien conspiracies and more at the io9 article.