"A Song of Ice and Fire" author George R.R. Martin likes to reference actual historical events in his novels, but for the ominous slogan "Winter is Coming" the Starks of Winterfell use to warn people of difficult times ahead, the author based it on his personal experience in Chicago.

Earlier, Martin credited Hadrian's Wall from the Roman Empire as the inspiration for the slogan, but recently, he told Entertainment Weekly that it was based on the experience he encountered as a freshman during the 1967 Chicago blizzard.

"The coldest winter was in Chicago. There was so much snow that winter, you couldn't see, all snow, all ice, and it was so very cold," he said. "I remember walking through the trenches and the tunnels of ice, the wind blowing so you couldn't even see. It's an experience that never left me."

Martin cannot believe that the HBO series "Game of Thrones" moved at such a speedy pace that the show has no more material left to use from his novels.

"The show, of course, has caught up to me, which I didn't actually think would ever happen," he admitted. "I had such a huge lead, but the truth is, I'm a very slow writer."

This was the same problem echoed by actress Gemma Whelan, who plays Theon Greyjoy's fearless sister Yara Greyjoy.

She said during an interview with the British Comedy Guide that the show actually started coming up with fresh storylines for itself back in season 5.

For season 6, Whelan said that they will only venture farther away from Martin's novels. Even those who have read Martin's novels feel uncertain about the characters' outcomes. "They've liaised with George RR Martin who writes the books, and gone off on their tangent, with his approval," she said. "So that's why people are even more interested in spoilers. It's funny isn't it, there's no other show like it."

Whelan also feels a certain responsibility not to give away any spoiler concerning the show, and the actress admits that she has to keep her actions in check all the time.

"Even when I said I'm going to Northern Ireland on Wednesday to you just now, I thought 'Oh, maybe I shouldn't say that.' You really watch your back on everything - 'Don't say too much,'" she said. "But at least it's been leaked that I'm going to be in it, so I can talk freely about that."