If you're a fan of the face-changing, shape-shifting, time-traveling TV show known as Doctor Who— and more specifically, a fan of the 2006-2010 run in which David Tennant was the 10th actor to play the lead role — then Christmas came early this year. And at the same time, in a very Who-ish, timey-wimey way, it didn't come early enough.

Tennant and his co-star Catherine Tate, who plays the Doctor's most mind-melded (literally, long story) human friend Donna Noble, came back to helm a 60th-anniversary run of three episodes over three successive Saturdays from November 25 through December 9. Written by Russell T Davies, also returning as showrunner for the first time since 2010, the specials are generating solid critical acclaim and audience appreciation. The first, "The Star Beast" reconnected the Doctor and Donna, emphasizing the mystery of why the Doctor had regenerated into a lookalike version of his previous self (Tennant is now technically playing the 14th Doctor). Then "The Wild Blue Yonder" sent them to the very edge of the universe to meet creepy, evolving versions of themselves. More horror awaited fans who realized Tennant and Tate's return to the spotlight was nearly over.

Now here comes "The Giggle" — not just a name like no other story title in 60 years of Doctor Whohistory, but a story that is set to shift the entire foundations of the show. And that's not because it introduces the 15th Doctor, played by Ncuti Gatwa, the first person of color to play the lead role on an ongoing basis. It's part of Davies' brand new design for the show going forward on Disney+ around the world, and on the BBC in the UK. One that makes a mere change of actor look like small potatoes. It has to do with the return of the Toymaker (Neil Patrick Harris), a godlike villain who first appeared in the show in the first Doctor's run in 1966.

"There will be controversial events in this episode," Davies told Doctor Who Magazinein a "Giggle" preview published this week. With what you might imagine as an appropriately big grin, he added: "It's a whole new way of looking at the history of Doctor Who, and I can't wait to see the reaction."

In other words, a lot of fans are going to be echoing the first line that we knew Gatwa would use in the episode: "Can someone tell me what the hell is going on?"

David Tennant's mind explodes.

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RTD (as Davies is universally known) warned fans Friday that they should try to watch the show live Saturday (at 6:30pm GMT, 1:30pm EST, and 10:30am Pacific) to avoid online spoilers — some of which will be posted on social media by the BBC itself.

In DWMhe went further, advising fans watch an episode commentary available (to UK viewers only, alas) on the BBC's iPlayer app:

"If you listen and watch the commentary on the iPlayer, I unroll a whole new Doctor Who mythology for you, based around the events taking place. And I'm explaining this to David Tennant, and his mind is exploding."

In other words, the change is subtle enough that even one of the stars of the episode didn't notice while he was filming it. And yet it's profound enough that Tennant, an extremely knowledgable Whovian himself, has to reorder the entire structure of the show in his brain.

This isn't the first time such a profound shift has come along; indeed, Whohistory is replete with them. In 1966, not long after the Toymaker's first appearance, the Doctor changed his face and personality for the first time, from balding and grumpy William Hartnell to mop-haired and puckish Patrick Troughton. We learned much more about why he could do that when we first met his people, the Time Lords, three years later. Which was also when we saw another profound shift: the Doctor was exiled to Earth, his TARDIS time-and-space machine rendered largely inoperable.

When RTD resurrected the series in 2005, he did so with another controversial change: The Doctor was now the last of the Time Lords, having supposedly eradicated both his people and his enemies the Daleks on the last day of an off-screen Time War. That all led up to an extremely satisfying climax in the 50th anniversary special in 2013, when Tennant and two other Doctors reverse that genocide. There have been small but satisfying changes too — such as "The Doctor's Wife," an episode in which guest writer Neil Gaiman revealed that the sentient TARDIS had been leading the Doctor around all these years, rather than the other way around.

The TARDIS' line, "I always took you where you needed to go," explained a lot about the Doctor's years of blundering around the universe while just happening to run into good trouble.

The Timeless Children and the Toymaker

Arguably less satisfying to most fans was the profound shift dreamt up by later showrunner Chris Chibnall. "The Timeless Children" was an episode that screened in March 2020, right at the beginning of the COVID-19 outbreak, and sometimes seemed as popular as a pandemic. We were told that the Doctor wasn't originally a Time Lord, but a mysterious being with mysterious origins discovered by a Time Lord founder. He/she (the Doctor was played by Jodie Whittaker at this point) had seen many lifetimes, and had his/her memories erased of all but the last 13.

Chibnall swept much of that mystery under the carpet in later episodes, with the Doctor ultimately deciding she didn't want to know about her previous incarnations. RTD was happy to make reference to it in "The Wild Blue Yonder," continuing in the best "yes, and" tradition of a storytelling canon that is essentially improvised.

The latest shift in canon starts with the Toymaker, a being we last saw fully in charge of his own game-and-toy-filled universe. "The Giggle" sees the Toymaker extend his powers to Earth, apparently able to "use the entire planet as his playroom," according to DWM. That means a whirling nightmare carnival of music, puppets, and Earthlings acting all weird. Or, given the fact that everyone now seems to be convinced of their own righteousness ... acting all normal? It also means that Donna has to step in to save a Doctor who has had his own toys (the TARDIS, the sonic screwdriver) taken away from him.

RTD so assiduously set up the mystery of why the 14th Doctor chose the 10th Doctor's face that it had to be answered — and manipulation by the Toymaker, an incredibly overpowered villain, seemed the most likely explanation.

What Ncuti did next.

Regardless of the resolution, RTD has set out his stall. Ncuti Gatwa's first season (and yes, he's already filming a second) will not be called season 14 of the new show, but season 1 of ... the new, new show?

For fans around the world, from the oldest BBC-watching cohort to the newest Disney+ sign-ups, this signals a very clear reboot: a point at which it is safe to start watching the adventures of this Time Lord and his blue box without requiring too much advance knowledge.

Everything we have learned about Gatwa's first full episode, a Christmas Day special on Disney+ and the BBC titled "The Church on Ruby Road," underscores this new start. The Doctor sings a full song, something we've never seen the character do before; the song will also be released as a Christmas single, RTD says. The Doctor also dances — not reluctantly, as in the 2005 episode titled "The Doctor Dances," but with utter abandon, in a nightclub.

This is New, New Who, then: A very Gen Z reboot. As older fans cope with exploded brains and (potentially) seething anger, the Doctor merrily shape-shifts once more, changing what we thought knew yet again. And the show proves it has the chops to last another 60 years. Because it always takes us where we need to go.