In a fantasy-genre story like "Game of Thrones," where fighting ability is a major factor in a person's apparent worth, it's not surprising that author George R.R. Martin put a lot of emphasis on size. But so did the casting agents: actress Gwendoline Christie is the real deal.

She stands at six-foot-three, and dedicated herself to a grueling gym regimen to get in shape for the role -- boxing, yoga, kickboxing and, she says, lots of protein.

"There was a lot of work because I didn't really have any muscle on me at all," she told Vulture.com. "It was a lot of packing on as much muscle mass as possible to just have the strength to carry out the stunts."

But she wasn't a total stranger to physical fitness prior to taking on the role. "I was a semi-professional gymnast as a child," she told "Access Hollywood," but her career was ended by a spinal injury, so she pursued acting instead.

She also revealed in the same interview that the attribute that makes her so striking on "Game of Thrones" -- indeed, that may have made her a star today -- was a source of pain as a child, and that she had trouble embracing it.

"It was hard ... All of the bullying and insults that I have received, very painfully over the years -- about being tall and about you know, my androgyny -- I was stepping into that."

Size was a factor in a few other "Game of Thrones" casting choices as well. Of course Peter Dinklage's height was a factor in being cast as a character nicknamed "The Imp," whose shortness is a defining factor in his life, but there were others as well.

The Clegane brothers, Sandor (a.k.a. "The Hound") and Gregor, were supposed to have been near-giants themselves, as are the actors who play them.

Rory McCann, who plays Sandor and is six-foot-six, appeared in the buddy-cop spoof "Hot Fuzz" (2007) as a comically large grocery store employee and occasional assassin. Ian Whyte (Gregor), seven-foot-one, served as a body double for the actress playing Madame Maxime, an actual giant in "Harry Potter and the Goblet of Fire" (2005).

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