Doctor Who Special 3, "The Giggle," put a new twist on regeneration as David Tennant vacated the leading role to Ncuti Gatwa with a historic bi-generation.
Longtime fans of Doctor Who will be more than familiar with the Time Lords' death-defying concept of regeneration.
The principle allows the Doctor to transform their body into a whole new person when they are mortally wounded, taking on a new face and personality while retaining the same memories and values.
Doctor Who's Confusing Bi-Generation Explained
Those who follow Doctor Who closely were well aware David Tennant's 14th Doctor was set to regenerate into Ncuti Gatwa's 15th Doctor in "The Giggle," but that process ultimately introduced a brand-new twist on the series' canon.
During his final standoff with Neil Patrick Harris' Toymaker on the U.N.I.T. helipad, the celestial villain blasted the Time Lord with a powerful laser so he could play his third and final game with the next Doctor.
The 14th Doctor started to regenerate as usual with Donna and Mel by his side as he said his final goodbye. Tennant began to glow and prepared to give way to his next self with the words, "It's time. Here we go again. Allons-y."
But things weren't quite that simple as the glowing stopped with no change in face before the Doctor asked Donna and Mel to "pull" each of his arms, saying it, "feels different this time."
The pulling saw the Doctor split down the middle between Tennant and Gatwa, who quickly hit it off as they completed their bi-generation.
The concept of bi-generation is brand-new to Doctor Who, as every regeneration before now has gone fairly smoothly from one face to the next. The 15th Doctor explained bi-generation as something that is "supposed to be a myth."
"Bi-generation! I have bi-generated! There's no such thing, bi-generation is supposed to be a myth But... Look at me."
As the Doctor fulfilled an ancient Time Lord myth in experiencing perhaps the first-ever bi-generation, it's unclear exactly what caused the split.
But with the threat of the Toymaker still at large, the pair teamed up to play a game of catch against Neil Patrick Harris' villain to banish him from the world.
Having beaten the Toymaker, the two Doctors were left with the question of what to do next, especially with only one TARDIS to go between them.
But alas, one last twist came as the TARDIS itself had also bi-generated, as a quick whack with a hammer duplicated the time machine, although one had some slight changes with a new jukebox and a wheelchair ramp.
On the topic of what to do next, the two Doctors set themselves on very different paths as the 14th Doctor mulled over the weight of his thousands of years of life, all the people he has lost, and those he has failed to save.
It certainly appeared all this trauma and burden was left upon the 14th Doctor to unwind and process. Meanwhile, Gatwa's 15th Doctor prepared to begin his era leading Doctor Who, changing his TARDIS lights to yellow and dematerializing the ship to begin his adventures this Christmas in another new special.
On the opposite end of the spectrum, the 14th Doctor settled down for retirement (or at least a break) on Earth with the Nobles, having himself become a member of the family, saying, "Who'd have thought, I ended up with a family."
Posed with the question of how long to stay with the Nobles, the Doctor explained he had finally come to understand what he had been fighting for all those years, declaring he had "never been so happy in [his] life."
DONNA: "You don't have to stay forever."
DOCTOR: "We'll see."
DONNA: "Do you miss it? Out there?"
DOCTOR: "Funny thing is, I fought all those battles for all those years, and now I know what for. This. I've never been so happy in my life."
But this certainly didn't seem to be a firm retirement based on his "we'll see" answer to what the future holds, along with having already taken trips to New York with Mel and gone for an off-world trip with Donna's daughter Rose.
Doctor Who's Confusing Double-Doctor Future Explained
Doctor Who now has a rather unique situation with two Doctors left to wander to the galaxy, and they seem to be taking very different paths. While the young and fresh 15th Doctor is off to continue his adventures, the weathered 14th Doctor is setting course for a peaceful rest from the action-heavy lifestyle.
Going forward, Doctor Who will focus on Gatwa's 15th Doctor and his sci-fi antics to come across time and space. The Sex Education star will enjoy his first solo adventure on Christmas Day in "The Church on Ruby Road" in which he will meet his new companion, Millie Gibson's Ruby Sunday.
The actor has already filmed the 2023 and 2024 Christmas specials, the whole of next year's Season 14, and production is underway on 2025's Season 15.
For now, it appears David Tennant is done with Doctor Who once again as the 14th Doctor has been left behind with the perfect happy ending. But that doesn't mean the door is firmly closed on his Time Lord hero, as his "we'll see" ending certainly implied more stories aren't completely off-the-table.
A decade ago in "The Day of the Doctor" 50th anniversary special, fans were introduced to the Curator. Played by 4th Doctor actor Tom Baker, the Time Lord was implied to be an incarnation of the Doctor who had returned to the familiar face, retired on Earth, and became the curator of a secret London gallery.
Between having the face of a familiar Doctor and retiring on Earth, perhaps the Curator is who Tennant's 14th Doctor will one day become while the other half of his bi-generation continues his legacy of exploring and saving the universe.
Doctor Who's 60th anniversary specials are streaming now on Disney+ in most territories and exclusively on BBC iPlayer in the UK & Ireland.
