What's Under Kit's Kilt in 'Pompeii'?

Game of Thrones star Kit Harington sits with ET's Nancy O'Dell to talk about one of the most incredible moments in human history -- and what he's wearing under that Gladiator kilt in his epic new thriller, Pompeii!

Game of Thrones star Kit Harington sits with ET's Nancy O'Dell to talk about one of the most incredible moments in human history -- and what he's wearing under that Gladiator kilt in his epic new thriller, Pompeii!

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"I wore a jockstrap for a solid four months, and I got too used to it, actually -- can't live without a jockstrap on," quips Kit. "In other things I do I'm always in big, big layers of clothing, so actually one of the appealing things about playing this part was the lack of that. And I was in a warm environment, I wasn't in the freezing cold, so I enjoyed the costume in this [movie]."

In theaters Friday, the epic Pompeii follows Kit's gladiator character, Milo, who finds himself in a race against time to save his true love Cassia (played by Emily Browning), the beautiful daughter of a wealthy merchant who has been unwillingly betrothed to a corrupt Roman Senator. As Mount Vesuvius erupts in a torrent of blazing lava, Milo must fight his way out of the arena in order to save his beloved as the once-magnificent Pompeii crumbles around him. Directed by Paul W.S. Anderson, Pompeii co-stars Carrie-Anne Moss, Jessica Lucas, Jared Harris and Kiefer Sutherland.

Related: Jon Snow?! Kit Goes Shirtless For 'Pompeii'

Watch the video for more as Kit explains how he got that crazy six-pack for the film -- and how he's related to real-life royalty!