The most memorable scene in Game of Thrones Season 4, Episode 8, “The Mountain and the Viper” was undoubtedly the moment where the Mountain squeezed Oberyn Martell's (Pedro Pascal) head until it exploded. It was gross and heart-wrenching and an incredible feat of special effects all at the same time, but how did they do it?

Alex Graves, who directed the episode, reveals the show’s secrets to The Hollywood Reporter. “I storyboarded it for, ‘This is when we're going to use Pedro, and this is when we're going to need some kind of a head that can implode,’" Alex says. “I sent our makeup supervisor off and he built this head to use for the shots. Then the visual effects guys took it home by putting a little swelling in the head, and making the one eye look really bad. The last composition that we barely got before the sun went down was of the two of them lying dead — the effects team made that even more gruesome. They rearranged some of his brain matter.”

We have to say, they did an amazing job... though we’re not sure we’re thankful for it! And now that we know how they made a head explode, they don’t have to do it ever again.

Source: The Hollywood Reporter

Catch the next episode of Game of Thrones Season 4 on June 8, 2014 at 9 p.m. ET on HBO.