The third episode of Doctor Who’s 60th anniversary celebration, “The Giggle,” did something the show had never done before—a bigeneration! The Doctor always “regenerates” whenever one actor gives way to another, but it’s always a direct change, one to another. “The Giggle” split the Doctor into two, one David Tennant’s Fourteenth Doctor, and the other Ncuti Gatwa’s Fifteenth.

And as you can bet, fandom responded to this very rationally and with an open mind. Just kidding, they did the exact opposite. “But! The Doctor is the same person each time, there’s not two separate people! Time Lord biology doesn’t work that way! Why has this never happened before?! The Doctor’s regenerations are sacred and unchangeable.”

No, no they aren’t folks. In fact, I’m going to say something controversial: regeneration in Doctor Who has NEVER been the same, any of the times it happened. Why should now be any different? Let’s take out of the equation the fact that the show is fictional and Time Lords aren’t real to begin with, even within the context of the show it’s mainly suggestion based on what makes for good drama at the time. As long as Doctor Who has had regeneration rules, it’s looked for ways to break them.

Jump To: Doctor Who‘s First Regeneration // Doctor Who Regenerates Again // Regeneration in the ’70s // Tom Baker (Four)’s Regeneration // Regeneration Arrives in Modern Doctor Who // River Song and Regeneration // Doctor Who‘s 50th Anniversary Changed Regeneration Again // A New Cycle of Regenerations // Time Lord Regeneration Encompasses Race and Gender // Thirteen’s Regenerations // The Timeless Child // Bigeneration in Doctor Who // Doctor Who Regeneration Is Ever Changing

The First Regeneration on Doctor Who

Regeneration as a concept, only exists because William Hartnell, the actor playing the Doctor, was getting too old to remember the tome of lines the character had every week. And we’re talking 40-some episodes every season. Tons of episodes. But what to do when the character of the Doctor is the main focus of the series, and is seemingly unique? One idea in season three was to just…change the actor. Hey, he’s an alien, the show is science fiction! The story “The Celestial Toymaker” presented an opportunity for this godlike trickster to just make the Doctor look different for lolz. They didn’t do that, and good thing, too.

The replace-the-actor-in-continuity angle needed to be something replicable. Cut to “The Tenth Planet,” the story that introduced the Cybermen, and which Hartnell already sat out two full episodes. At the very end of the fourth episode, the Doctor wanders away from his companions, appearing in a lot of discomfort. He mutters something about his old body wearing thin. He then collapses on the floor of the TARDIS. What’s really interesting about William Hartnell’s transformation into Patrick Troughton is how sparse and inexplicable it is. The TARDIS groaning sounds play over it and the visuals flash in an out. It’s not entirely clear what’s even happening, or even that the TARDIS itself isn’t causing the transformation.

Doctor Who Regenerates Again

The Second Doctor, three seasons later, was also wearing thin. Mostly, this was just Troughton getting tired. At the end of season six, Troughton’s final season, the wheels were coming off the production cart a little bit. So much so that the final serial, “The War Games,” just kept ballooning as they were making it in lieu of any other usable scripts. It went from four episodes into the eventual 10 episodes, the second longest single serial in the show’s history.

Partway through the serial, the Doctor meets a character called “The War Chief,” who turns out to be another member of the Doctor’s race. We’d met other such characters before but with the War Chief, we learn for the first time the name of the Doctor’s race—the Time Lords. Despite running from them since the show began, things get so bad that the Doctor has no choice but to signal to the Time Lords to intervene, giving himself up in the process.

The Time Lords put him on trial for the horrible crime of helping people and so decide to exile him to Earth, removing his ability to fly the TARDIS, and forcing his face to change. The Time Lords don’t say “you’re going to regenerate, a thing we all do all the time.” Rather they say “your face has changed before, it will change again.” Unlike “The Tenth Planet,” we don’t actually see the Second Doctor turn into the Third Doctor. Once again it’s not clear if this is a thing that his body can do normally and they’re just forcing it, or if it’s a punishment that wouldn’t have happened otherwise.

Regeneration in the ’70s

Beginning with the Third Doctor, we get the word “regenerate” in relation to the Doctor changing shape. This would begin major lore creation for the series with regards to Time Lords. The Third Doctor’s change proved it was something Gallifreyans had the ability to do. However, it remained unclear whether this is something all Time Lords do or just something Time Lords can do.

That all changed during the Tom Baker era. In the now classic story “The Deadly Assassin,” the Fourth Doctor returns to Gallifrey in order to foil an assassination plot against the Time Lord president. Along the way, the Doctor discovers it’s the Master, decrepit and decaying at the end of his life cycles, trying to utilize the Gallifreyan citadel’s mystical Eye of Harmony to give him a new set of regenerations. One of the Doctor’s allies says “After a Time Lord’s twelfth regeneration, nothing can save them.”

Tom Baker's Fourth Doctor in full Time Lord regalia in Doctor Who The Deadly Assassin.

This was, in no small way, massive. After 13 years on the air and three onscreen regenerations, the show slaps us with lore that, whether by nature or design, Time Lords can only regenerate 12 times, meaning 13 separate lives. Retroactively, the show tells us the first two Doctors did in fact properly regenerate, and moreover, they’d put a number on it.

Now, in fairness to writer and script-editor Robert Holmes, it seemed HIGHLY unlikely at the time the Doctor would ever need to worry about this. Since we live in the future, it saddled Doctor Who with storytelling limitations that future writers would have to try to figure out how to deal with.

Tom Baker’s Regeneration Had a Time Ghost

After a whopping seven seasons in the role, Tom Baker’s scarf began to unravel for the last time. His final story, “Logopolis” is about entropy and a planet run by math. I do not want to explain it further. Throughout the story, the Doctor and companions keep seeing this weird ghostly figure watching them. This thing just stands around and the Doctor seems to know what it is but won’t say.

As the story comes to a close, and the Doctor falls from a great height after defeating the Master, he says “it’s the end, but the moment has been prepared for.” The then gestures to the white alien thing who walks over and like, merges with the Doctor’s body which triggers the regeneration. Nyssa has the ADR’d line “The watcher…he was the Doctor all the time.”

Hang on. So this weird ghost was a spectre of the Doctor’s next incarnation? Like, tapping his watch? “Come on, curly, we’re burning daylight here.” Why does this happen? How does this happen? And how did Nyssa, who literally only showed back up an episode prior, know all about how Time Ghosts work?

Jump To: Doctor Who‘s First Regeneration // Doctor Who Regenerates Again // Regeneration in the ’70s // Tom Baker (Four)’s Regeneration // Regeneration Arrives in Modern Doctor Who // River Song and Regeneration // Doctor Who‘s 50th Anniversary Changed Regeneration Again // A New Cycle of Regenerations // Time Lord Regeneration Encompasses Race and Gender // Thirteen’s Regenerations // The Timeless Child // Bigeneration in Doctor Who // Doctor Who Regeneration Is Ever Changing

Doctor Who Made Regeneration a Rule…and Then Broke It

The next several regenerations were all weird in their own way. The Fifth turned into a guy he’d met before. Number Six regenerated from hitting his head on the TARDIS console. The Seventh Doctor was gunned down by Triad gangs in the 1996 TV movie on Fox. They bent the rules but never broke them. By time the series returned in 2005 under Russell T Davies, regeneration had been fully codified into Doctor Who‘s DNA.

However, following the Ninth Doctor’s regeneration into the Tenth, things got a bit more complicated. “The Christmas Invasion” finds the newly minted Tenth Doctor in bed for most of the adventure, cooking after regenerating. When he finally gets up, he runs his gob and has a sword fight with a bad alien skull had man. During the fight, the baddie cuts his hand off, but because he’s still in the first 12 hours of his regeneration cycle, he grows a new one.

In the cliffhanger to the previous episode, “The Stolen Earth,” a Dalek zaps the Doctor in the heart and he starts to regenerate. The viewing public knew David Tennant was leaving the show so it was a great and shocking surprise. However, the first seconds of “Journey’s End” has the Doctor heal his wounds with the regeneration energy and then shoot the rest off into his severed hand, which has been in the TARDIS in a water-filled specimen tank after Torchwood found out and Captain Jack Harkness brought it back to him.

This makes the hand grow into a separate version of the Doctor but—and this is a big thing—is a one-hearted, non-regeneratable human. All of this was basically to give Rose Tyler, who was full-on in love with the Doctor but got banished to another dimension, a boyfriend. It’s so weird. It’s SO weird. 

Fans call him “The Handy Doctor.” Presented without commentary.

The Wild Saga of River Song

Series 6 is a whole thing which is very complicated and deals with the origins of girl-out-of-time River Song. It turns out River is actually the daughter of the first married couple companions, Amy and Rory. We learn that she can regenerate and was kidnapped as a baby and programmed to be an assassin to kill the Doctor. Why can she regenerate? Well, the show tells us since she was conceived in the TARDIS while it was traveling through the time vortex, the baby was somehow fused with Time Lord DNA.


In the series’ eighth episode, “Let’s Kill Hitler,” we find that the Doctor is for-sure going to die but then River bestows upon him her remaining regenerations through a kiss. So she’s a regular ol’ human person now, but the Doctor is back to having the same exact amount of regenerations he was already up to.

Doctor Who‘s 50th Anniversary Changed Regeneration Again

The 50th anniversary was the first multi-Doctor story, really, since the ‘80s and brought back David Tennant to team up with Matt Smith, and folks, it’s so good. But, for our purposes, it also has some very particular things to say about regeneration.

At the end of the previous series, the Doctor and his companion Clara Oswald end up within the Doctor’s own time thread, and they see versions of all his previous selves. One of them is unknown to Clara, who had met all the ones we’ve talked about. The Doctor says “We don’t talk about that one,” whose name is apparently Bruno.

The cliffhanger shows John Hurt, and it says introducing John Hurt as the Doctor. And my dudes, people lost their damn mind. How can this be!? He’s not one of the canonical Doctors! The numbering! Think of the numbering!

This was all part of the wild mix of necessity and contractual requirements writer Steven Moffat had to contend with. The new series, and especially the Moffat era, had made sure to confirm in continuity that the Eleventh Doctor was, in fact, the Eleventh Doctor. But because the presumed Doctor to fight in the Time War—the Ninth Doctor—was played by an actor who did not want to return, Moffat had to figure something else out. Moffat created a new Doctor that fit in between the Eighth and Ninth, who didn’t count himself as a Doctor. The War Doctor.

What Regeneration Limit?

In the very next episode, “The Time of the Doctor,” Matt Smith’s Eleventh Doctor strands himself on the planet Trenzalore, protecting the town of Christmas for hundreds of years. He gets markedly ancient and then he explains to Clara that he’s out of regenerations. He counts them thusly: Each regen we see from 1-7, then Eighth Doctor to War, then War to Ninth, Ninth to Tenth, then Tenth to Handy Tenth, then Tenth to Eleventh. So he’s out of regenerations, apparently.

Lucky for him, he finds his home planet in a crack in time and through that, the Time Lords bestow on him a new cycle of regenerations. 

People were mad about this. That’s a get out of jail free card, a deus ex machina, a third trope that means the same thing. My response is: Yeah, of course it is. Do you want the show to be over? If you never change canon, if you never think of clever ways out of painting yourself in a corner, or a corner someone else painted you in 40 years prior, then you can’t keep a series going for 60 years. Feel free to stop watching and make your head canon that the Doctor died and we’re done. But we’re not done.

Jump To: Doctor Who‘s First Regeneration // Doctor Who Regenerates Again // Regeneration in the ’70s // Tom Baker (Four)’s Regeneration // Regeneration Arrives in Modern Doctor Who // River Song and Regeneration // Doctor Who‘s 50th Anniversary Changed Regeneration Again // A New Cycle of Regenerations // Time Lord Regeneration Encompasses Race and Gender // Thirteen’s Regenerations // The Timeless Child // Bigeneration in Doctor Who // Doctor Who Regeneration Is Ever Changing

Time Lord Regeneration Encompasses Race and Gender Too

After the Twelfth Doctor era, the Doctor changes genders for the first time on screen, going from Peter Capaldi to Jodie Whittaker. This was a pretty groundbreaking moment, however to quote a previous regen, “The moment had been prepared for.”

Earlier in the Eleventh Doctor era, we hear about a friend of his named the Corsair who had changed gender upon regeneration. Then there’s Missy, of course, a female-presenting version of the Master. And just for good measure, in the story “Hell Bent,” the Doctor shoots a Time Lord general who then regenerates from Ken Bone, and old white man, into T’Nia Miller, a younger Black woman.

Wild Thirteenth Doctor Shenanigans

In the episode “The Fugitive of the Judoon,” the Doctor works to protect a woman named Ruth played by Jo Martin from being unduly captured by the intergalactic rhino police guild, the Judoon. As the episode goes on, we eventually learn, along with the Doctor, that Ruth is a version of the Doctor in hiding who had used a chameleon arch to wipe her memory and make her human. Naturally the Doctor assumes this is a later incarnation, because she doesn’t remember this version, but the Ruth Doctor also doesn’t remember the Thirteenth Doctor. So, a mind-wiped future incarnation? NO.


We learn that Doctor Ruth (not the sex one) was a pre-Hartnell Doctor whom Division, which is basically the Time Lord CIA, the government of Gallifrey used to carry out clandestine murder missions. At some point, we’re further led to believe, the Doctor’s memory was fully wiped, given a full new set of regenerations, and as far as they were concerned, they were living their first life.

Now this is obviously a huge, huge revelation. If you thought the War Doctor mucking up the 1-11 numbering was a problem, try not even knowing what number this new one is! Is she Doctor Zero? Is she negative numbers Doctor?

The Timeless Child

The Thirteenth Doctor hardly gets time to wrap her head around this before she gets a whole new wallop of backstory. The Master, ever the thorn in the side of things, has wiped out the citadel on Gallifrey, because he learned a fact he couldn’t handle. Eons ago, a Gallifreyan scientist named Tecteun found a strange child that seems to have come out of nowhere. This child has the innate ability to turn into a new person on the genetic level whenever they die. And yes, a child dies on Doctor Who.

Tecteun then figures out a way to harness this energy and give it to other Gallifreyans to keep them alive for millennia longer than they otherwise would have been. Simultaneously they’d developed time travel, so couple with effective immortality, they became the Time Lords.

Time Lord government imposed the 12 regeneration limit, because who wants to live forever, as Freddie Mercury once said. The child, if you hadn’t figured it out yet, was the Doctor, who was not only exploited for their natural resource, but forced into servitude in the Time Lord CIA who basically used them as a Winter Soldier, mind-wiping and regenerating them after every mission.

The amount of rewriting to lore this creates is gargantuan, not to mention it brings into question all of the times throughout the years we’ve heard the Doctor muse about their childhood on Gallifrey. Did they turn the Doctor back into a child when Division was done with them? Because we know from the Twelfth Doctor episode “Listen” that the Doctor was a child living in a barn at one point. We also know they grew up and went to school with the Master, so again I ask, how and why?

One Face, Two Face, Old Face, New Face: Bi-Generation in Doctor Who

Eventually, the Thirteenth Doctor’s time arrived. She stands on a mountain and regenerates into…David Tennant?! Well, it’s not unprecedented at this point! It’s canonically a new Doctor, the Fourteenth, but he’s reusing the Tenth Doctor’s face a) because it’s for anniversary special reasons, and 2) so once and future showrunner Russell T Davies can right some wrongs with the character of Donna. And we already know revisiting faces is a thing.

Which brings us, finally, to “The Giggle,” the third of the three Doctor Who 60th anniversary specials.


The Toymaker, the trickster god from another plane of existence and who has powers of reality manipulation, zaps the Fourteenth Doctor and he starts to regenerate again. But no! He doesn’t regenerate, at least not quite. He asks Donna and returning Sixth and Seventh Doctor companion Mel Bush to pull on his arms and this splits him in two, with one remaining David Tennant and the other the trouserless Ncuti Gatwa, the Fifteenth Doctor.

The show makes a point of explaining this has never happened before, it’s new and unique due to the Toymaker’s reality manipulation. It’s not a re-generation, it’s a bi-generation. There are now two Doctors, the former of which seemingly mortal.

And you wanna know something? I love it. I think it’s genius. Why, why, why keep doing the same damn thing you’ve been doing for 60 years? Especially when, basically all of those previous examples were not “the same” in any way?

Jump To: Doctor Who‘s First Regeneration // Doctor Who Regenerates Again // Regeneration in the ’70s // Tom Baker (Four)’s Regeneration // Regeneration Arrives in Modern Doctor Who // River Song and Regeneration // Doctor Who‘s 50th Anniversary Changed Regeneration Again // A New Cycle of Regenerations // Time Lord Regeneration Encompasses Race and Gender // Thirteen’s Regenerations // The Timeless Child // Bigeneration in Doctor Who // Doctor Who Regeneration Is Ever Changing

Doctor Who Regeneration, Now and Forever

Regeneration was one of the most brilliant conceits a TV production ever dreamt up. You might be able to get away with recasting a character once and have the audience buy it. But only Doctor Who has built it into the fabric of the show. Change is the show’s key to longevity. Updating the cast every few years, bringing in not only new companions but a new Doctor who is the same Doctor but not, keeps the series fresh.

There’s a reason the first episode of a new Doctor is routinely the most watched of any era. People are excited about how the new person will be in the role. And that’s still what’s happening. Nothing is different on that front. We’re still getting brand new adventures with a new actor in the lead. So what if now they have no regeneration limit or the Doctor can split rather than fully change?

A younger me would have been annoyed by this but I also have changed with the times. As long as we’re still getting a show that’s willing to take weird risks and swing for the fences, even if they don’t make sense, I say go for it. If you can justify it and make it resonate with the characters, I’m here for it.

Kyle Anderson is the Senior Editor for Nerdist. He hosts the weekly pop culture deep-dive podcast Laser Focus. You can find his film and TV reviews here. Follow him on Instagram and Letterboxd.