Okay for this I've done some research and it seems a number of celebs believe in them I found 17 to start with but I'm sure there are more out there the key would be an interview or statement that the celeb believes they exist in some fashion be it the usual stereotypes of being in the same room, pictures, communication, that kind of stuff but being this site it can include admitting to wanting an extra terrestrial sex session (looking at you Demi Lovato) so let's get this started
Demi Lovato (admits to swearing off men and willing to have sex with aliens given the chance)
Victoria Justice
Ariana Grande
Kylie Jenner (afraid of them but fascinated to talk if they don't act aggressively)
Rihanna
Miley Cyrus (admits to being chased down by UFO)
Dallas Lovato
Kelly Clarkson (willing to travel the cosmos if aliens offered)
Kim Kardashian (camped out at area 51 to see aliens and failed)
Kendall Jenner
Katy Perry
Gigi Hadid
Kourtney Kardashian
Scarlett Johansson (well she did admit to having an alien raccoon on speed dial)
Vanessa Hudgens
Stella Hudgens
Jennifer Lawrence
Megan Fox (says if you tell her aliens exist she's willing to go with the idea)
I'm sure I missed a few so if anyone wants to add to the list with credible evidence celebs admit to seeing aliens here's your chance and maybe we can get some fun story ideas out of the deal