The 'Game of Thrones' dragons purrs are actually recordings of tortoises having sex.
The hit HBO fantasy show features three fire-breathing creatures owned by the Mother of Dragons, Daenerys Targaryen - played by Emilia Clarke - and one of the giant flying lizards named Drogo gets its voice from the peculiar source.
Paula Fairfield, the show's sound designer, told WNYC radio show Radiolab: "The groan of the male actually became, with some work and adjustments and stuff, the basis of Drogon's purr with Daenerys.
"I have sounds I might choose simply by certain personality traits that I might want to push forward. She named that dragon at Khal Drogo, her hot late husband, so Drogon is like her lover. He's whistling at her all the time, he's whistling at her butt and saying, 'Ooh baby.' "
Paula decided to give the three dragons their own personalities in order to bring the mythical creatures down to earth.
She said: "They're very powerful, they can be very scary, they can be very destructive. But what's kind of magical in 'Game of Thrones' is that the intimate scenes also melt your heart and bring you closer to these characters that should be burning your face off."
The seventh season of the show saw a dramatic twist when one of Daenerys' beloved "children" sadly killed by the Night King, the leader of the White Walkers - who subsequently brought it back to life and was seen riding it as the series came to an end.
Sophie Turner - who is also set to reprise her role as Sansa in TV - also revealed that 'Game of Thrones' won't be returning to screens until 2019.
Originally the show was supposed to air later in the year than normal due to the longer episodes scheduled for season eight, but now Sophie broke the shocking news for 'Thrones' fans.
Fans will have to wait to see who wins the Iron Throne.
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