"Doctor Who" Season 9 Spoilers — As the long-running British sci-fi television program, "Doctor Who," returns this fall, a brand new character might be introduced together with the appearance of "Game of Thrones" star Maisie Williams. According to executive producer and showrunner Steven Moffat, Williams' role will be totally different for the 18-year-old actress.

"Doctor Who," the BBC-produced film, is a television series that depicts the adventures of the Doctor (Time Lord), who is a space and time-traveling humanoid alien. The series has been airing for over five decades and is a significant part of British popular culture. Now with "Doctor Who" Season 9, the Doctor (Peter Capaldi) along with his companions will fight a variety of foes while working to save civilizations and help people in need.

With Williams joining "Doctor Who" Season 9, one of the biggest questions is the role she'll be playing on the series. Earlier this month, the series a glimpse of its upcoming season at the San Diego Comic-Con. According to Seattle Pi, Williams' character will challenge the Doctor in surprising ways when she appears in at least one episode of Season 9.

To shed light about the rumors on Williams' role, "Doctor Who" showrunner Steven Moffat revealed at the Television Critics Association that all the fans' theories and the rumors are false since she will be playing a brand new character.

"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... It's a significant role. We're not throwing her away. 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, A.V. Club noted.

Aside from Williams, fans will also see a different Clara (Jenna Coleman) when the show returns this fall. 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," Coleman said. "There's a sense of fearlessness, of reckless abandon. She can throw herself into adventures head first."

Meanwhile, Lucy Lawless has been proposed to appear on "Doctor Who" Season 9. As per Fansided, bringing Lawless on the series would be the perfect opportunity to revisit Leela's character while also giving a nod to Xena. Lawless could also play a character who is a relative, friend, or even enemy of Leela's, most likely from Sevateem.

Meanwhile, catch "Doctor Who" Season 9 as it returns Saturday, Sept. 19 on BBC America.