The man behind a Facebook event that jokingly suggests storming Area 51 says he never expected it to get as large as it has. 

As of Friday afternoon, more than 1.7 million people had signed up for the "Storm Area 51" event on Sept. 20 and another 1.3 million said they were interested. It's also spawned countless memes and a direct response from the U.S. military. 

Matty Roberts spoke to Las Vegas station KLAS and said when he first posted the event in late June only a couple people signed on, then it "took off out of nowhere." 

And if there were any doubts about his plans, Roberts said it was completely satire and he tried to make it seem as much as a joke as possible.  

"There's definitely some people that are taking it seriously," Roberts acknowledged to KLAS I-Team reporter George Knapp. 

Roberts added that he started getting concerned when more than 500,000 had pledged to join the Area 51 effort. "I was just like the FBI is going to show up to my house. It got a little spooky from there," he explained to KLAS.  

But with so many people signed up, U.S. military officials aren't joking around. 

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An Air Force spokesperson told multiple media outlets that "the U.S. Air Force is aware of the Facebook event" and warned that "any attempt to illegally access the area is highly discouraged." 

While Roberts insists the event is all a joke, an inn close to Area 51 told the New York Times it's gotten an unusually high number of reservations for that date. 

The owner of Little A'Le'Inn told KLAS the inn's 10 rooms are all booked around the Facebook event's Sept. 20 date, so she's clearing 30 acres where people can camp and listen to a few bands who are planning to be there.