Ian McElhinney and Steve Toussaint will feature in the 'Doctor Who' series finale.
Ian McElhinney
The 'Derry Girls' star and the 'Prince of Persia' actor will join current Doctor Jodie Whittaker and her team in the two-part 'Ascension of the Cybermen'/'The Timeless Children', although the details of their roles are being kept under wraps.
'Game of Thrones' actor Ian had a "blast" shooting his scenes.
He said: "I very much enjoyed my time on 'Doctor Who'.
"The team were a delight to work with and everyone was very supportive and welcoming. All in all it was a blast."
And 'Upstart Crow' star Steve was just as proud to be involved in the iconic programme.
He said: "It was an honour to play a part in the giant of British (and World) TV that is 'Doctor Who'.
"What's not to like? I had such a great time working with Jodie and 'the Fam'; another one off the bucket list!"
Show bosses have teased the two actors have helped bring the current series of the show to a "dramatic conclusion".
Executive producer Matt Strevens said: "We were delighted to have Ian and Steve on board the TARDIS for the drama filled two-part finale.
"Their wide-ranging talent and versatility as actors help bring series 12 to a dramatic conclusion. They were an absolute joy to work with and we can't wait for viewers to see them in action."
Showrunner Chris Chibnall has revealed the final episode of the series will run for longer than usual, but refused to give any details about it.
He told Doctor Who magazine: "I can't tell you anything about this episode.
"The Timeless Child is mentioned as far back as 'The Ghost Monument' [2018], and the final episode of this series is where some of those questions get answered. It's a huge, emotional finale with lots of Cybermen. And it runs for 65 minutes.
"It's both epic, and personal. This is what you're always looking for in a series finale - the way the big, universe-threatening story impacts on the personal lives of your characters. And categorically that's what's happening in this episode.
"In 'Spyfall Part One' [the Doctor and her companions are] buoyant and they're having fun. Where we leave them at the end of episode 10 is an entirely different place."
Tagged in Jodie Whittaker