Astronaut Scott Kelly Reveals Real Story Behind Video of Him in Gorilla Suit Aboard Space Station

Scott Kelly/Twitter Scott Kelly

It can get monotonous in space, especially if you've been up there for a while.

So being a thoughtful brother, Mark Kelly, a retired NASA astronaut, decided to send his identical twin Scott — who would be aboard the International Space Station for almost a year in 2015 and 2016 — a surprise to lighten things up.

"I was on the phone with my brother one day and he said, 'Hey, I'm sending you a gorilla suit,'" Scott Kelly, now 57, tells PEOPLE. "And I said, 'Why?' And he goes, 'Because there's never been a gorilla in space before.'"

Mark, now an Arizona senator, vacuum packed the suit and sent it with a cargo delivery on an unmanned SpaceX mission, which blew up in June 2015.

"The next time I was on the phone with my brother, he goes, 'I'm sending you another gorilla suit,'" Scott recalls.

This attempt was successful.

As the story goes, Scott dressed up in the gorilla suit and then hid. A video that he posted to Twitter in February 2016 shows him coming out of a big white bag and chasing British astronaut Tim Peake, who then rushes to get away in zero gravity.

A Twitter user shared 15 seconds of the hilarious footage on Jan. 9, but mistakenly credited Mark as the wearer of the gorilla costume.

The video has since been viewed over 9 million times and received more than 356,000 likes and 75,000 retweets.

"Of course people liked it. How can you not like space gorilla?" says Scott, adding that he was "surprised it made the rounds of the internet again after all these years."

It's also been shared on many other social media accounts.

As it turns out, Peake wasn't surprised by the antic.

"That's all staged," says Scott. "That's why he's floating around, swimming in air, we wanted it to look funny."

"It was the end of my year in space," says Scott, who retired soon after his return in 2016, "so you need a little humor.'

Scott had more fun with other crew members who had no idea a gorilla was on board. At one point, he hid in one guy's sleeping quarters in the gorilla suit.

"When he went to open the door, I busted out of there, and afterwards I was a little worried that I could have given him a heart attack or something," says Scott, laughing.

He also made a surprise visit to the Russian astronauts aboard the space station.

Bill Ingalls/NASA via Getty Images

"I floated down to the Russian segment," he says. "When they saw it, they were just laughing like you wouldn't believe."

Plus, Scott recorded an educational video while dressed in the suit.

"One reason I decided to do this is to have a video like that is pretty useful with kids," he says. "A gorilla in space gets everyone's attention."

NASA says on its website that the gorilla suit was Mark's surprise for Scott when they turned on 52 on Feb. 21, 2016.

"I don't remember that," says Scott, "but maybe that's the case."

RELATED: Inspiration4 Reveal They Felt the 'Overview Effect' in Space — What to Know About the Phenomenon

Scott, who lives outside of Denver, is a public speaker and author of the bestseller Endurance: My Year In Space, A Lifetime of Discovery.

As for what happened to the gorilla suit? That went out with the trash.

Says Scott: "I didn't want to be responsible for what anyone else would do with a gorilla suit in space."