Why Is David Tennant Back In Doctor Who? An Investigation

As first revealed back in May 2022, former "Doctor Who" star David Tennant is returning to the seminal sci-fi series alongside his former companion Catherine Tate as Donna Noble as part of the show's 60th anniversary. Whovians got their first glimpse of the returning Doctor in the recent special that marked the end of Jodie Whitaker's time in the TARDIS. However, Tennant's appearance in "The Power of the Doctor" wasn't exactly under the circumstances that Whovians expected to see the Tenth Doctor again. Well, I guess it's actually the Fourteenth Doctor now!

In the episode, due to reasoning that doesn't exactly make sense, the Thirteenth Doctor is forced to regenerate into the Master. During this time, when Sacha Dhawan's mad Time Lord is in control of The Doctor's body, she meets a mysterious figure in what is essentially the Ancestral Plane. Dubbed the Guardians of the Edge of Existence, this being inside The Doctor's consciousness can change their appearance to resemble her past regenerations — specifically the first (David Bradley), fifth (Peter Davison), sixth (Colin Baker), seventh (Sylvester McCoy), and eighth (Paul McGann). They tell the latest incarnation of the Doctor that a Time Lord's body is still unstable following a regeneration, but especially after a forced one, so time is running out to take back their body.

The Doctor eventually regains her body thanks to Yaz, but is mortally wounded in her final confrontation with the Master. After one last ice cream cone with her closest companion from this era of the show, the Doctor's time has come to actually regenerate. And when she does, she emerges with the familiar teeth of Tennant's Doctor. 

But how is that even possible? Some clues from some the past decades of the series might offer a bit of an explanation.

Chris Chibnall's run on "Doctor Who" was largely met with a mixed response, but the former showrunner certainly had some big ideas with lots of potential. One thing that he addressed was the Doctor's ability to regenerate past the Time Lords' maximum regenerations of twelve. 

By the time Chibnall boarded Team TARDIS, we had already learned of the existence of the War Doctor (John Hurt) and how each number after him from the Ninth Doctor (Christopher Eccleston) onward was technically off count, which means Nine was actually the character's tenth regeneration, Ten was the eleventh regeneration, and so on. With Peter Capaldi's Twelfth Doctor actually being the thirteenth incarnation of the character, the adventurer from Gallifrey should have died rather than regenerating into Jodie Whitaker's Thirteenth Doctor.

But as we learned from the season 12 episode "The Timeless Children," the Doctor actually isn't the Time Lord from Gallifrey that they believed themselves to be. They were discovered near a boundary to another dimension by Tecteun, a Shobogan traveller and scientist who became one of the first inhabitants of Gallifrey. Once she learned of the Timeless Child's ability to regenerate, Tecteun extracted DNA from the child and was able to splice it into her own body and her Shobogan companions so that they could regenerate as well — but only up to twelve times.

On top of the revelation that the Doctor is the biological foundation of the Time Lord society, we also learned that a clandestine organization called the Division enlisted their services as they got older, then erased any memory of their missions. Basically, that would all explain the existence of the Fugitive Doctor (Jo Martin) and another incarnation we previously met with an affinity for art.

The Doctor having the ability to regenerate more than twelve times is a topic that has been explored in the past, but mostly in talking about the future. During the show's 50th anniversary special, titled "The Day of the Doctor," Steven Moffat introduced the Curator, a mysterious figure who resides in the Under Gallery and resembles the Fourth Doctor (Tom Baker). 

It's implied that the Doctor becomes this character when he retires from his adventuring ways and decides to become "a humble curator" for an art gallery. While speaking to the Eleventh Doctor (Matt Smith) at the end of the episode, the Curator explains that he looks familiar because the Doctor never forgets a face and decides to revisit a few in the years to come, "but just the old favorites." So with this in mind, there is a precedent for a Doctor's regeneration to bring back an old look, even though Whovians didn't expect it to happen in the timeline for a good while.

Of course, David Tennant isn't the only familiar face returning for the upcoming anniversary special. Former companion Donna Noble will be making an appearance as well, but no one knows how that's even possible (except returning showrunner Russell T. Davies). 

When we last saw Donna, the former temp worker from Chiswick was imbued with the totality of the Doctor's knowledge accumulated over the course of his long, wibbly-wobbly, timey-wimey life. Since her human brain can't handle all of that information (despite using it to defeat Davros in the season 4 finale, "Journey's End"), the Doctor erases Donna's memory of him and all their adventures together against her will in order to save her life. If she does remember, the results could be fatal for her. We get a glimpse of this in the final episode of the Tenth Doctor's run when the "DoctorDonna" nearly regains her memories and a failsafe installed by the Doctor is triggered and knocks her out with a telepathic pulse.

When it comes to Donna's return, there's not a lot of information available. There's some speculation that "Heartstopper" actor Yasmin Finney's Rose is actually Donna and Shaun's daughter, but there's no confirmation on that rumor. If that is the case, then maybe Donna actually has retained some flicker of her time with the Doctor deep down in her memory. Or maybe Russell T. Davies just loves having a Rose in the TARDIS. Either way, Donna's presence alongside the Fourteenth Doctor cannot be a coincidence. And there's one more fan theory that may explain it.

Based on Davies' warning of "Doctor beware!" after the casting, fans assumed that Neil Patrick Harris is playing a villain when he appears on "Doctor Who" next year. The showrunner confirmed this theory when he called NPH's character (via Den of Geek) "the greatest enemy the Doctor has ever faced." While that tagline could apply to a number of foes in the show's rogues gallery, if we're going by looks alone, the actor looks like an old-timey toymaker in some of the photos shared since the initial announcement. But what if he wasn't just any toymaker? 

Originally a thorn in the First Doctor's side, the Celestial Toymaker was essentially a mix of John de Lancie's Q from "Star Trek: The Next Generation" and Marvel's Arcade. The villain — who was played by Michael Gough (whom many may recognize as Bruce Wayne's butler, Alfred, from a number of Batman movies) in a mostly missing serial from the third season of the Classic Who era — is an all-powerful immortal entity that takes joy in toying with his victims. Literally. He would bring people into his Celestial Toybox and force them to take part in his twisted games that were often impossible to win.

But are we really suggesting that Harris is playing this role just because he looks like a literal toymaker? Of course not! If he was in fact playing this classic character, then that could explain the return of Donna. It's possible that the Fourteenth Doctor finds himself in the Toymaker's clutches and the antagonist plucks Donna from the Doctor's memories to mess with our unknowing hero's head. The trauma associated with their adventures is surely enough to throw the Doctor off his game during his latest round with the Celestial Toymaker. Weirder things have happened on this show.

Speaking of weird things happening on "Doctor Who," one of the more unusual occurrences in "The Power of the Doctor" was the Doctor's clothes regenerating along with their "new" face. As far as I can tell, that's never happened before in the series' long history. Even earlier in the episode when the Doctor is forced to regenerate by the Master, he emerges from the process wearing the Thirteenth Doctor's clothes. But during the regeneration at the end of the episode, the Fourteenth Doctor ends up in a variation of the Tenth Doctor's trademark attire of a trench coat over a suit. 

At first, I thought that this could have been the Celestial Toymaker's doing as well. Maybe he made it look like the Doctor reverted to an "old favorite" just to mess with him. But then when Russell T. Davies and the rest of the official "Doctor Who" channels started referring to Tennant as the Fourteenth Doctor, that somewhat ruled out that possibility.

More likely, this has to do with the botched forced regeneration. There's really no good explanation why, since this is uncharted territory, but that has to factor in somehow, right? Either that or the device that the Master shot the Doctor with during the final moments of their battle affected the impending regeneration. Either way, Chibnall really left a lot on the table when it comes to regenerations, so hopefully RTD picks up on some of those loose threads and addresses them with either the Fourteenth Doctor or Ncuti Gatwa's Fifteenth Doctor, because some kind of explanation would be nice.

Unfortunately, we'll have to wait a while for those answers. Keep coming up with your thoughts and theories because "Doctor Who" returns in November 2023 on Disney+.