Jodie Whittaker, the 13th Doctor in the BBC’s long-running and immensely popular “Doctor Who” series, regenerated on Sunday, Oct. 23, revealing David Tennant, who was the 10th Doctor, as the 14th Doctor.

Tennant and Catherine Tate are reprising their roles for the show’s 60th anniversary, and the BBC has confirmed that they will appear in three special episodes, set to air in November 2023.

“David Tennant, previously known as the 10th Doctor, is now also known as the 14th Doctor. Confused? Don’t worry, he seems a little perplexed too,” the BBC said in a statement.

“Doctor Who” began in 1963 and follows the adventures of a Time Lord known as The Doctor, an extraterrestrial being with a human appearance. The Doctor travels the universe in a time-travelling spaceship called the Tardis.

The next Doctor, played by “Sex Education” star Ncuti Gatwa, will take control of the Tardis after Tennant, with his first episode airing over the festive period in 2023.

“Doctor Who” showrunner Russell T. Davies said: “If you thought the appearance of David Tennant was a shock, we’ve got plenty more surprises on the way. The path to Ncuti’s 15th Doctor is laden with mystery, horror, robots, puppets, danger and fun. And how is it connected to the return of the wonderful Donna Noble? How, what, why? We’re giving you a year to speculate, and then all hell lets loose.”

For the specials, “Heartstopper” actor Yasmin Finney joined the cast as Rose, it was revealed in May, and there’s also a mysterious new character played by Neil Patrick Harris.

Davies had said at the time: “Life on ‘Doctor Who’ gets brighter and wilder, how can there be another Rose? You’ll find out in 2023, but it’s an absolute joy to welcome Yasmin to the ‘Doctor Who’ set. We all fell in love with her in ‘Heartstopper,’ one of those shows which changes the world – and now Yasmin can change the Whoniverse.”