Doctor Who Maisie Williams

Doctor Who Boss on Maisie Williams' Character: 'She's Not Playing [Spoiler]'

Doctor Who fans, prepare to amend your theories about Game of Thrones star Maisie Williams’ mysterious role in Season 9.

“She is not playing a returning character,” showrunner Steven Moffat revealed Friday at the Television Critics Association summer press tour in Beverly Hills. “She’s a brand new character. She’s not someone from the Doctor’s past.”

Moffat is confident Doctor aficionados will not be disappointed by the reveal. “Once you see what she’s up to on the show, you’ll appreciate what a clever idea it was,” he said. “It’s a significant role. We’re not just getting star value and throwing it away. It’s a great part, and she’s terrific in it.”

Other takeaways from the panel:

* Will star Peter Capaldi follow in Matt Smith and David Tennant’s footsteps and exit the title role after three seasons? “Peter is going to play the part for the rest of time,” Moffat joked. “It’s the only job in television where everyone asks you when you’re leaving.”

* Clara’s “perspective on life has changed” in the new season, her portrayer Jenna Coleman previewed. “She’s no longer divided between Earth life and Tardis life. There’s a fearlessness and reckless abandon as she and the current Doctor throw themselves into adventures first.”

* As for Michelle Gomez’ Missy, “the role that she fulfills in the new season is rather different from what she did last season,” Capaladi teased. “She gives the Doctor a hard time.”

Doctor Who Season 9 bows Sept. 19 on BBC America.