Los Angeles, May 16 : Actors David Tennant and Catherine Tate are returning to 'Doctor Who', reuniting for new scenes that will coincide with the show's 60th anniversary celebrations in 2023. Tennant and Tate will reprise their respective roles of the 10th Doctor and companion Donna Noble, reports 'Variety'. The pair's tenure on the series spanned from 2005 to 2010. When the characters were last seen together, the Doctor had to wipe Donna's memory in order to save her life. "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?" showrunner Russell T. Davies said in a statement. "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." Tennant had returned to the role of the Doctor once before, teaming up with then-Doctor Matt Smith in 2013 as part of the show's 50th anniversary celebrations. The news comes only one week after the official reveal of 'Sex Education' star Ncuti Gatwa as the newest actor to play the Doctor. Gatwa's tenure in the role will begin in 2023, after Jodie Whittaker's current incarnation concludes with one more special episode later this year. Tennant and Tate's tenure on 'Doctor Who' remains the height of the series' popularity, helping lead the show to new international audiences. The 2008 series featuring the two brought in an average audience of more than eight million viewers per episode. /IANS