It's one thing to believe that there are other forms of life in the universe, but another to claim to have actually seen them.
Just think about it: the universe has trillions of galaxies, which have trillions of stars, and those stars have many of their own planets. It's a lot to take in, but there's an undeniable possibility that life exists outside of planet Earth.
However, alleged UFO sightings, mermaids, and seeing green alien life forms are tales that should be strictly for science fiction movies.
1. Russell Crowe
The Oscar-winning actor shared a video in early 2013 supposedly capturing a UFO sighting.
The pictures were taken outside his office in Sydney, Australia. He tweeted, "A friend and I set up camera to capture fruit bats rising from Botanic Gardens. This was a big surprise."
If that doesn't look photoshopped, I don't know what does...
2. Khloe Kardashian & Kendall Jenner
After seeing some "spooky" lights in the sky, these "it girls" took to Twitter convinced that they experienced their first UFO sighting.
These tweets below are pretty self-explanatory.
"Khloe and I are freaking out right now over this UFO situation," wrote Kendall.
Khloe and I are freaking out right now over this UFO situation— Kendall (@KendallJenner) November 8, 2015
"I believe!!!! "@KendallJenner: you guys..I swear I just saw a UFO," tweeted Khloe.
I believe!!!! "@KendallJenner: you guys..I swear I just saw a UFO"— Khloé (@khloekardashian) March 12, 2013
Turns out the lights were a planned Trident II (D5) missile test flight, but these half-sisters beg to differ.
Khloe had a response for the US Navy: "What do we expect people to say? Obvi they are going to say it's a meteor shower. I'm such a conspiracy theorist let me enjoy this."
3. Billy Ray Cyrus
The "Achy Breaky Heart" singer not only thinks the mullet should make a rebound, but that alien life has visited Earth.
In 2011, he tweeted about his first alien encounter: "O.K... my first UFO sighting. Looks like 5 or 6 disk like shapes hovering. Special moment 4 DAD."
O. K. . ..my first U F O sighting.Looks like 5 or 6 disk like shapes hovering. Special moment 4 DAD http://t.co/aG23vJKL— Billy Ray Cyrus (@billyraycyrus) October 23, 2011
In 2014, Miley was in the Bahamas when she questioned the object that "zipped" in the sky.
"My dad told me it was a satellite. But the way it zipped off was really weird."
4. Sigourney Weaver
Who better to believe in aliens than Alien star Sigourney Weaver?
In a 2011 interview with German magazine TV Spielfilm, Sigourney said, "I think there's a department in [the US] government which is exclusively dedicated to quashing reports about aliens. And that's so unfair. It would be nice if we weren't just able to read about it in the tabloids."
One of these next celebrities thinks she actually came in contact with an alien life form...