If longtime fans of Doctor Who felt that Jodie Whittaker's first season — Season 11 — was a little too light on explaining the sprawling mythology of the series, then Season 12 is pretty much the exact opposite. Between the return of the Master, the ascension of the Cybermen, and even the return of very obscure villains from the Fifth Doctor era, Doctor Who Season 12 dipped into the 57-year-old toy box perhaps more than any other contemporary season in recent memory.
Outside of the 50th Anniversary special — "The Day of the Doctor" — in 2013, there's never been this many changes to Doctor Who canon in one year. Here's a brief recap of why the 2020 Season 12 of Doctor Who shook things up the most, and what each of these changes might mean going forward.
**Spoilers ahead for all of Doctor Who Season 12.**
EARTH-DWELLING HUMANS TURN INTO MUTANTS CALLED THE DREGS IN AT LEAST ONE FUTURE
In "Orphan 55," we learned that at some point in the Earth's future, climate change will cause the humans left behind to mutate into creatures called the Dregs. Oddly, most of this checks out with existing Who canon.
From the Fourth Doctor serial "The Ark In Space" to the Eleventh Doctor episode "The Beast Below," the notion that Earth was evacuated because of solar radiation has been a running theme. Solar radiation is a direct result of the atmosphere being destroyed. The Doctor does tell Graham, Yaz, and Ryan that this future could be changed, but so far, Who canon has told us that this is happening. The difference now is, we had a very, very specific glimpse into what that aftermath looked like on Earth.
TIME LORDS HAVE AT LEAST TWO BRAINS
Though hinted at in the Twelfth Doctor episode "Extremis," this season confirmed that Time Lords have at least two — maybe three — brains. And now, in Season 12, two episodes confirm the plural brain thing.
In "Praxeus," the Doctor refers to her "brains" in the plural. And then, in "The Timeless Children," the Master did the same thing.
A SECRET VERSION OF THE DOCTOR LIVED ON EARTH IN 2020 UNDER THE NAME "RUTH"
In Episode 5 of this season, "Fugitive of the Judoon," we met a previously unknown version of the Doctor, hidden on Earth. Thanks to "The Timeless Child," we know now this Doctor had worked for an organization called The Division, which operated outside of Time Lord law. We have no idea how many years or incarnations are in-between this version of the Doctor and William Hartnell's "First" Doctor.
THE DOCTOR ISN'T REALLY A TIME LORD, AND THE 'TIME LORDS' STOLE REGENERATION FROM HER AS A CHILD
At this point, we don't actually know what kind of alien species the Doctor hails from, but we do know that the Time Lords were an invented name, created by the Shabogans after they stole the genetic ability to regenerate from "The Timeless Child," who is, in fact, the earliest version of the Doctor. This opens up a lot of questions.
Back in the 1996 TV movie Doctor Who, the Eight Doctor said he was half-human. The Twelfth Doctor mentioned this idea in "Hell Bent," too, when talking to Lady Me about the notion of "the hybrid." Perhaps, the hybrid that the Time Lords were so focused on back then wasn't the Doctor at all, but perhaps, the Doctor's adoptive mother, Tecteun. If Tecteun was the real hybrid, then suddenly, the Time Lords torturing the Twelfth Doctor in "Heaven Sent" makes a little more sense.
This secret was a pretty big deal.
A RANDOM, PREVIOUSLY APOCRYPHAL TOM BAKER EPISODE IS NOW PIVOTAL, AND 100 PERCENT CANON
Related to the big reveal in "The Timeless Children," during a huge flashback sequence, we saw a scene from the Tom Baker Fourth Doctor episode "The Brain of Morbius." Though the "The Deadly Assassin" later established the 12-regeneration rule in late 1976, in January 1976, "The Brain of Morbius" presented the possibility of several hidden versions of the Doctor.
For years, most fans disregarded this scene as an error, simply because the true canon of the Time Lords hadn't been established yet. But now that we know the Doctor had several hidden lives before the ones we've seen, this episode was not only made canon by association but also because a scene from it appeared onscreen in the Season 12 finale.
BTW, ALL THE TIME LORDS ARE DEAD (AGAIN)
As established in episode 2 of season 12, "Spyfall Part 2," the Master burned Gallifrey, killing all the Time Lords there. Presumably, this is the same version of Gallifrey that all the Doctors saved by placing it in a pocket universe in "The Day of the Doctor," and later visited in "Hell Bent." By the end of season 12, all the Time Lords are dead, again, even though they are briefly brought back to "life" as Cybermen/Time Lords (Cyber Lords?) But, all of those Cyber Lords are killed in the end, too. So, just like in 2005, with the Ninth Doctor, the Thirteenth Doctor is once again, the Last of the Time Lords, even though she's also the first of the Time Lords, too.
BY THE END OF THE SEASON, THE DOCTOR POSSIBLY LEFT THREE SEPARATE BRAND-NEW TARDISES JUST LYING AROUND
In "Spyfall Part 2," the Doctor steals the Master's TARDIS (disguised as a house) to get her and Ada Lovelace out of WWII and back to the Doctor's own TARDIS. She later drops off Ada in her correct time, using her normal TARDIS, but... presumably, left the Master's TARDIS in the 21st century? Maybe? She says she is going to "reclaim my own TARDIS," but we don't know what she does with the Master's.
Then, in the finale, "The Timeless Children," the Doctor steals two TARDISes from Gallifrey, one she uses to send Yaz, Ryan, Graham, and the far-future human refugees back to the 21st century. This TARDIS uses its Chameleon Circuit to disguise itself as an apartment building as it materializes. Next, at the end of "The Timeless Children," the Doctor takes yet another TARDIS — this one disguises itself as a tree — back to the planet where she and "the Fam" had left her regular TARDIS. And, like the other two TARDISes, she just leaves it there.
So, if you count the dinner TARDIS being flown by Clara and Lady Me from Season 9, that means there are now a total of four TARDISes (not counting the Doctor's!) hanging out in the Whoniverse unaccounted for. Considering all the Time Lords are dead (again) the fact that so many random TARDISes exist right now feels super significant. Will Graham, Yaz, and Ryan keep the one they have? Will an old enemy find the tree TARDIS? And what about the Master's TARDIS? Did he steal it back sometime between "Spyfall Part 2" and "The Timeless Children"?
When Doctor Who returns in early 2021 with "Revelation of the Daleks," there's a chance one of these extra TARDISes will be explained. As for the rest? We'll have to wait and see.