Don’t mess with Khal Drogo.

Just when you thought you were done being shocked by Jason Momoa for the day — he shaved off his beard for the first time seven years, in case you missed it — HBO has revealed a truly wild tale about the actor.

On Thursday, the network released a new series of animated shorts called Backstories, in which the creators of some of their hit shows share behind-the-scenes secrets. For the Game of Thronesshort, David Benioff and D.B. Weiss teamed up to tell the story of when Momoa, 39, accidentally sent one of them to the hospital.

As the story goes, the cast and crew were shooting season 2 in Belfast. Momoa, whose character died in season 1, returned to shoot a dream-like scene in which he reunites with his wife Daenerys Targaryen (Emilia Clarke). After they were done, they all went out drinking to celebrate being back together.

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“Jason was one of our favorite people ever on the show, and very strong,” said Benioff, 48. “And that’s not TV makeup — in real life, he’s just a big, strong dude.”

“So I’m looking at Momoa and Momoa’s talking about beating someone at the slap game,” he continued. “I was like, ‘I’ll take you at the slap game.’ I was like, I’m going to challenge the Khal, because if I beat the Khal, I am the Khal.”

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Jason Momoa (left) and David Benioff | Jeff Kravitz/FilmMagic; Kevin Winter/Getty More

Having consumed an “anesthetic quantity” of beers, the two started playing the game, which essentially consists of slapping the other person’s hands as many times as you can until you miss, then switching.

“I got a few pretty good slaps and then I missed,” Benioff began. “Then it was my turn. I put my hands out and he starts slapping.”

The rest of the group only started paying attention when they noticed a “kind of firecracker sound” going off.

“I looked over and his hands were bright red,” Weiss, 47, said of Benioff. “He was still going, and that was when all of us decided to put our conversation on hold to watch this contest.”

“I looked in Momoa’s eyes, I saw no mercy there,” Benioff recalled. “But I wouldn’t quit, because, you know, I had my pride. I had my dumb pride.”

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Clarke was the one to first point out the state of Benioff’s hands.

“When we looked down to his hands, his hands didn’t look right,” Weiss admitted. “His hands were a lot bigger than his hands normally are.”

But Benioff figured the swelling would go down on its own.

“I just thought it was one of those things where it looks pretty bad — yes, they look like catcher’s mitts with bubonic plague on them, but it’s going to be better tomorrow,” he said.

When Benioff woke up the next morning, his hands had “doubled in size overnight.” He flew back to Los Angeles, where he was greeted by wife Amanda Peet.

“I was kind of trying to hide my hands a little bit,” he admitted. “But it didn’t work because they were so monstrous.”

When she saw his hands, Peet immediately drove her husband to the emergency room, where a doctor ran a few X-rays.

“Her diagnosis was that Jason Momoa had squished my hands,” Benioff revealed. “So, it just goes to show, don’t challenge the Khal.”

Game of Thrones airs Sundays (9 p.m. ET) on HBO.