Williams has begun filming her scenes for the sci-fi show in Cardiff, Wales, not far from her home town, Bristol.
“I’m so excited to be working on 'Doctor Who,' as it’s such a big and important part of British culture,” Williams said on the first day of filming. “I can’t wait to meet the cast and crew and start filming, especially as we’ll be shooting not too far from my home town.”
While not much is known about Williams’ character on “Doctor Who,” it appears she will be just as mischievous as Arya.
“It’s not possible to say too much about who or what she’s playing, but she is going to challenge the Doctor in very unexpected ways,” lead writer and executive producer Steven Moffat said. “This time he might just be out of his depth, and we know Maisie is going to give him exactly the right sort of hell.”
In Season 9 of “Doctor Who” Peter Capaldi returns as the doctor along with co-star Jenna Coleman, who plays companion Clara Oswald.
Williams joins the ranks of a whole host of actors who have visited both Westeros and the TARDIS in previous seasons, including Thomas Brodie-Sangster, Joe Dempsie, Diana Rigg, and Liam Cunningham. Paul Kayne, who plays Thoros of Myr on “Game of Thrones,” will also appear in Season 9 of "Doctor Who."
“Doctor Who” will not return to BBC America until the fall. However, Season 5 of “Game of Thrones,” which premieres April 12, reportedly contains big changes for Williams’ character as she leaves Westeros, where she has been disguised as a peasant boy for three seasons, for the exotic and foreign city of Braavos.