You come at the Khal, you best not miss.

HBO has released a new series of animated behind-the-scenes stories from several of its shows, and the inaugural installment is devoted to Game of Thrones because what else is anyone talking about right now anyway? And as it turns out, the show's stars aren't the only ones who've suffered gnarly injuries in the production process, and that slap game the Sand Snakes were playing in Season 5 was based on a very real situation that happened behind the scenes.

In the video, which features some brutal animation, co-showrunners David Benioff and D.B. Weiss join forces to tell fans about the time actor Jason Momoa accidentally sent Benioff to the hospital after a rollicking pub game.

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Benioff explains that when Momoa returned to the show to film his cameo in the dreamy hallucination scene from the Season 2 finale, the cast and creatives all went out for a drink, and Benioff decided to challenge Momoa to the slap game.

"I was like I'm going to challenge the Khal because if I beat the Khal, I'm the Khal," Benioff explained of his drink-induced bravado. Of course, he might've been fooled by the somewhat serene scenes Momoa filmed as Khal Drogo that day, because the writer soon found out the hard way that Momoa is still a beast who can do some serious damage.

"I looked in Momoa's eyes, I saw no mercy there. But I wouldn't quit because I had my pride," he remembered. Soon after, co-star Emilia Clarke apparently called on the fellas to end their little game, but by then it was already too late.

"It was one of those things where I was like, yeah, it looks pretty bad. It looks like catcher's mitts with kind of bubonic plague on them, but it's gonna be better tomorrow," said Benioff.

The next day, Benioff's hands were swollen to twice their size, and by the time he flew back to Los Angeles, they were so swollen that his wife had to take him to the emergency room. The official diagnosis was that his hands had been "squished" by Momoa, instead of broken, but Benioff learned an important lesson from the encounter all the same: "It just goes to show don't challenge the Khal." He probably should've known that already, though.

HBO's other new "Backstories" segments center on Barry and Insecure.

Game of Thrones airs on Sundays at 9/8c on HBO.

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Jason Momoa, <em>Game of Thrones</em>Jason Momoa, Game of Thrones