The BBC announced Williams, known for playing Arya Stark in HBO's Game Of Thrones, will step foot in the TARDIS and has already begun filming.
“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 her 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.”
“We’re thrilled to have Maisie Williams joining us on Doctor Who," showrunner Steven Moffated added. "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. 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.”
Doctor Who returns this Fall.