David Tennant and Catherine Tate are to return to 'Doctor Who' for the show's 60th anniversary.
The stars will reprise their roles as the Tenth Doctor and companion Donna Noble for the show's milestone anniversary in 2023.
Russell T Davies, who is returning as showrunner on the long-running BBC sci-fi programme, announced the news on social media, writing: "THEY’RE BACK! The Doctor and Donna! But… how?! He wiped her memory! If she remembers, she’ll die!
"But, but… is it a flashback? A dream sequence? A lie? A fantasy? A parallel universe?! Alt Doctor? The Land of Fiction?! You’ll find out in 2023 as Doctor Who hits its 60th – diamond! – anniversary! @bbcdoctorwho."
The news follows the announcement that 'Sex Education' star Ncuti Gatwa has been cast as the Fourteenth Doctor and Russell has now teased a "spectacular" return for David and Catherine.
In an official statement on the 'Doctor Who' website, Russell said: "They’re back! And it looks impossible – first, we announce a new Doctor, and then an old Doctor, along with the wonderful Donna, what on earth is happening?
"Maybe this is a missing story. Or a parallel world. Or a dream, or a trick, or a flashback.
"The only thing I can confirm is that it’s going to be spectacular, as two of our greatest stars reunite for the battle of a lifetime."
Meanwhile, Ncuti revealed he was "deeply honoured" to be chosen as Jodie Whittaker's replacement as the Doctor after being confirmed for the role.
He said: "There aren’t quite the words to describe how I’m feeling.
"A mix of deeply honoured, beyond excited and of course a little bit scared.
"This role and show means so much to so many around the world, including myself, and each one of my incredibly talented predecessors has handled that unique responsibility and privilege with the utmost care.
"I will endeavour my upmost to do the same."