One of the biggest questions surrounding Season 9 of Doctor Who is not necessarily whether we'll be subjected to the same poorly crafted stories of Season 8, but rather who Game of Thrones' Maisie Williams will be playing when the show returns in September.

First glimpsed in the trailer that debuted earlier this month at Comic-Con, Williams' character will challenge the Doctor in unexpected ways when she appears in at least one episode of Season 9. When pressed for more details by reporters at the Television Critics Association fall previews on Friday, executive producer and showrunner Steven Moffat revealed that all of our theories about her character are useless, because Williams is playing a new character.

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"She is not playing a returning character; she's a brand new character," he said. "She's not someone from the Doctor's past... unless I'm lying."

Possible Doctor-level lying aside, Moffat did say that her role wouldn't be small(er on the outside). "It's a significant role. We're not throwing her away," he said. "We're not getting the star value and doing nothing with it. It's a great part and she's terrific in it. But I would say it will develop in unexpected ways."

"I think once you see what she's up to in the show you'll appreciate what a clever idea of Brian Minchin's that was," he added.

Watch the new trailer for Season 9

Additionally, fans should expect to see a different Clara when the show returns. Her perspective on life has changed after Danny's death at the end of Season 8. "She's no longer divided between Earth life and TARDIS life," said star Jenna Coleman. "There's a sense of fearlessness, of reckless abandon. She can throw herself into adventures head first."

Doctor Who returns Saturday, Sept. 19 at 9/8c on BBC America.