The title of the Doctor Who Centenary Special may explain how David Tennant returns. Jodie Whittaker's time as the Thirteenth Doctor is sadly coming to an end. She will appear in one final episode, the Doctor Who Centenary Special, entitled "The Power of the Doctor." Releasing as part of the BBC's centenary celebrations, this will see the Doctor confronted by Sacha Dhawan's Master and an army of villains he has united against her.
This is expected to be the final episode of Doctor Who released in 2022, but 2023 will be an even bigger year for the world's longest-running sci-fi TV show - its 60th anniversary. Russell T. Davies is returning as showrunner for three specials, and surprisingly he isn't the only one. David Tennant appears to be reprising the role of the Doctor as well, and the fact he's been seen with the Whittaker-era TARDIS suggests this isn't some sort of "missing adventure." Rather, somehow Whittaker is going to regenerate into a past form. David Tennant's return to Doctor Who remains a mystery, but the BBC may have just dropped a major clue.
The BBC has been oddly secretive about the title of the Doctor Who Centenary Special, only letting it become public knowledge within a month of the 90-minute episode's release. At first glance, it's difficult to see why; The Power of the Doctor is quite a bland and formulaic title, following the pattern of specials under former showrunner Steven Moffat. But the titular "Power" is clearly the Doctor's ability to regenerate, with the Chibnall era revealing there are no limits to the Doctor's lives. The Master is aware of this, and it's reasonable to assume he will aim to either steal or weaponize the Doctor's regeneration energy in some way. Such an act could conceivably cause something to go wrong with the regeneration, causing what could be called a "degeneration."
How Degenerations Fit Into Doctor Who Lore
This would fit with a classic Doctor Who regeneration story, published in comic strip form in 1979. Doctor Who Weekly #17-18 featured a two-part story in which the Fourth Doctor encountered a powerful temporal phenomenon, and began to regress through his past regenerations. Something similar could happen in The Power of the Doctor; regenerations draw upon the power of the time-space vortex, meaning similar temporal manipulation could complicate the Doctor's regeneration, leading her to take on a familiar face. Such a twist was foreshadowed by The Day of the Doctor, the 50th anniversary special, in which Matt Smith's Tenth Doctor encountered a character named the Curator played by Tom Baker, hinted at being a future Doctor who had taken on an old favorite face.
Doctor Who's marketing has been excessively secretive of late, but it's possible there was a reason this time. As formulaic as the title of the Doctor Who Centenary Special may seem, it potentially offers a major clue to the story's plot, and in doing so hints at a way Tennant could return as the Doctor. Hopefully it won't be long before the BBC release further details, including a new trailer for the Doctor Who Centenary Special.