"I posted it on like June 27th and it was kind of a joke," Matty Roberts told Nevada's KLAS-TV. "And then it waited for like three days and like 40 people, and then it just completely took off, out of nowhere. It's pretty wild."

Now, over 1.7 million people have signed up for the Facebook event, with another 1.3 million people having expressed interest in the event.

Roberts, who had initially communicated with NPR anonymously via Facebook messenger, says he was worried that the FBI would show up at his house.

Roberts says he came up with the idea after Joe Rogan interviewed Area 51 whistleblower Bob Lazar and filmmaker Jeremy Corbell. During the interview, Lazar claims to have been involved in all types of alien matters while working at a branch of Area 51 known as "S4," where he was tasked with reverse-engineering the propulsion system on one of nine flying saucers kept on the base.