Doctor Who's showrunner still feels as green as when he took the job back in 2010.

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The iconic sci-fi series has found fans around the world, and showrunnner Steven Moffat believes no matter how many episodes he has under his belt, the series will always be as daunting as ever.

"The terrifying thing about Doctor Who is that you discover at the start of every new show that you have learned absolutely nothing at all, that it's brand new. It always makes you feel completely like 'oh, I thought I'd got the hang of this but I have no idea what to do," Moffat told Doctor Who Magazine (via Doctor Who TV) joking that he "feels genuinely as inadequate and amateurish today as I felt on my first day."

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Moffat just wrapped up his fourth season with Doctor Who, and his tenure included the highly anticipated 50th anniversary. In the wide universe of all of time and space, however, Moffat does not believe the series is becoming repetitive, nor should it be predictable.

"A show dies when it's reliable like a pair of old slippers," Moffat said, according to the Radio Times. "If any reviewer says that about a show that show is gone within a year." 

Find out more when Doctor Who returns this Christmas. Click the video below to see a preview for the 2014 Christmas special.