It's not too surprising that "E.T." singer Katy Perry believe in UFOs. "I see everything through a spiritual lens. I believe in a lot of astrology. I believe in aliens," the pop star says in the February 2014 issue of GQ. What is surprising, however, is that she's not alone—pun intended.

"Unconditionally" singer Perry, 29, is just one of many celebrities who is open to the idea that there is life on other planets. Actress Megan Fox, for example, is a big fan of History's hit series Ancient Aliens.

"Everyone thinks I'm crazy," the Teenage Mutant Ninja Turtles star said during a March 2012 appearance on The Ellen DeGeneres Show. "It's all about the theory that these megalithic structures were possibly built by—not necessarily like little green aliens, but maybe future humans that they call ancient astronauts—that did some sort of time travel. Something extraterrestrial was involved."

Tom Cruise, star of the science fiction movie War of the Worlds, is also a believer. "Are you really so arrogant as to believe we are alone in this universe? Millions of stars, and we're supposed to be the only living creatures? No, there are many things out there," he said in 2007. "We just don't know."