NOTE: This post contains SPOILERS for Doctor Who season 8.
From the addition of a new Doctor, played by Peter Capaldi, to the controversial gender change of the Master, aka Missy (Michelle Gomez), Doctor Who season 8 was divisive. On top of new actors, and a darker tone, standalone episodes of the series faced a wide spectrum of critical response - even the most well-received chapters also endured tongue-lashings from well-known Who commentators. However, in spite of the ups, downs, and disagreements over what worked and what didn't, there's no doubt that season 8 established a compelling foundation for the cast and writers to build on in season 9.
As usual, concrete story details remain under Steven Moffat's tight-guard at BBC; yet, casting announcements, table read footage, leaked set photos, and the latest Doctor Who season 9 trailer have provided some tantalizing teases that fans are already attempting to unpack. The biggest question? The identity of Maisie Williams (Game of Thrones) - who is confirmed for two episodes of the upcoming series and featured in a post-logo stinger at the end of the trailer. Given that The Doctor appears to recognize the girl, we're breaking down five possibilities of who Maisie Williams could be playing.
Of course, our list is not all-inclusive, if you have your own ideas, we invite you to share them in the comments after reading our theories!
A Never Before Seen Character
When it was first announced that Williams was joining the cast for a pair of episodes, it wasn't clear if the actress would portray an entirely new character - or be the new face of a returning Doctor Who cast member. Based on the season 9 trailer, The Doctor clearly recognizes Williams - indicating that the pair have a history; however, since Williams will appear in two episodes, fans cannot be sure that this reunion isn't just the conclusion to a story beat that was introduced earlier in season 9.
If that were the case, and Williams is playing an completely new character, then almost anything is possible. Still, previous season 9 hints have suggested that "It’s almost like he’s running from something, something that, if it ever catches him, will turn his life upside-down," while Capaldi himself has indicated that "she shifts in cosmic ways." Considering the return of Missy, not to mention potential tampering with the fate of Gallifrey in the 50th Anniversary Special, it's possible that the Doctor or Missy could have released the Could've Been King or The Nightmare Child from their imprisonment within the Last Great Time War.
Both abominations have been mentioned in the modern series but never shown on screen - creating an opportunity for Moffat to build a new Doctor Who hero (or villain) on the back of one-off lines of dialogue from the David Tennant years. Nevertheless, with Williams scheduled to appear in episodes titled "The Girl Who Died" and "The Woman Who Lived," it's equally possible that her character's story is entirely self-contained - or merely a jumping off point for future appearances.