Doctor Who said goodbye to Jodie Whittaker's 13th doctor during Sunday's third and final special. 

In one of the most shocking moments in Doctor Who's history, Whittaker's Thirteenth Doctor regenerated with a very familiar face.

That's right, folks.

David Tennant returned to the series as the Fourteenth Doctor.

Obviously, we know that won't stick for very long because the BBC announced Sex Educations Ncuti Gatwa would take on the iconic role in 2023.

We learned earlier this year that Tennant was one of many returning faces for the next season that will celebrate 60 years of Doctor Who.

Tennant opened up about returning to the iconic role on BBC's Today radio show on Monday morning.

“I think I was worried before I got there that it might be difficult to get in the groove again,” he said, adding that it was just like riding a bike because it was “weirdly straightforward.”

Tennant added that “there’s bit of a precedent in this show that all Doctors maybe turn up for a special now and again, but usually in cohort with the current team."

"So to get another run round the park was a little joy I never saw coming," the star added.

“What a lovely, lovely thing to get to revisit something that was such a wonderful, happy, significant time in my life,” he added.

“It’s like being given the loveliest present. It’s been an absolute joy.”

Given that fans were left confused about the ending because it had been reported Gatwa would take on the role, showrunner Russell T Davies released a statement.

“If you thought the appearance of David Tennant was a shock, we’ve got plenty more surprises on the way!” Davies said.

“The path to Ncuti’s Fifteenth Doctor is laden with mystery, horror, robots, puppets, danger and fun! And how is it connected to the return of the wonderful Donna Noble (to be played again by Catherine Tate)? How, what, why? We’re giving you a year to speculate, and then all hell lets loose!”

Yes, we have a year before the series returns to the air, but it is cool to know that Tennant is back in the role ... for now.

The reason for the delay is thought to be the cast availability, with Gatwa hard at work shooting the fourth season of Netflix's Sex Education.

It's rare in today's world for long-running series to pack a punch in the storytelling department, but fans were shocked to the core by the events of Sunday's finale.

And, if you're dying to know what happens next, have a look at the trailer below.

Paul Dailly was an Associate Editor for TV Fanatic.Follow him on X.