In the final of three Doctor Who 60th anniversary specials, David Tennant's Fourteenth Doctor was killed by the Toymaker. However, instead of regenerating, the Time Lord underwent a shock bi-generation, meaning the Fourteenth (Tennant) and Fifteenth (Ncuti Gatwa) Doctors now exist at the same time.
Some could argue that's always been the case, of course, as the very nature of time travel means every version of the Doctor is out there somewhere!
While the next series of Doctor Who will put the spotlight squarely on Gatwa, the expectation is that he and Tennant will eventually share the screen again. There's even been chatter about the Fourteenth Doctor getting a spin-off, something we know would make a lot of fans very happy.
However, in an interview with Radio Times, Tennant dialled back expectations.
"The Doctor’s happy. He is in a garden in Chiswick, being made mac and cheese by Bonnie Langford!" the actor exclaimed. "The door is not any more open than it ever was, because in Doctor Who if you want to bring someone back, there are endless ways of doing it. It’s very much the end of the story."
When the site put it to Tennant that his Doctor might need to protect Earth if Gatwa's version is elsewhere, he countered by saying, "You could also say, 'Why has Patrick Troughton not landed here?!' It unpicks if you think about that too much. I’m retired! The Fourteenth Doctor is retired!"
Despite that, Tennant says the show remains a "huge part" of his life and noted that his recent return was a "real treat."
"Bi-generation, we discover, is an ancient myth of the Time Lords where, instead of a new body taking over from the old body, the new body separates from the old body, and both are left alive," showrunner Russell T Davies said last year of the Doctor's new status quo.
"Bi-generation is a new thing; it’s the 60th," he continued. "Imagine how much fans love new things, and really rejoice when this happens [Laughs]."
"Actually, I’ve had this idea for years. I’ve always wanted, instead of going back and meeting old Doctors, I’ve always wanted the Doctor to talk to his new version. Why has it never been done before? How can you resist the two of them having an adventure at the same time?"
Doctor Who returns with new episodes this May. In other news, the BBC just dropped some exciting news for fans...