David Tennant’s final(?) special as the Fourteenth Doctor is a giddy, overstuffed callback to the excesses of the Russell T. Davies era — with a suitably overbaked guest star and a dashing preview of adventures to come.

CLOISTER BELL ALERT: Spoilers ahead for “The Giggle,” so all those who haven’t seen it yet, turn left. But if you have, don’t blink, we’ll go over every little detail. Allons-y!

“I don’t want to go.” Those words, uttered by David Tennant’s Tenth Doctor in 2010 (then again, cheekily, in 2013), are beginning to feel a bit like prophecy. After all, here we are, at the end of the hotly-anticipated trio of specials meant to usher us from the poorly-received Chris Chibnall era of the show to the glitzy, big-budget Disney reign of Doctor Who. “The Giggle,” the third of these (with a Christmas special on the way — God bless us, everyone), has to keep a lot of balls in the air: Give a new-old Doctor, one with the face of an old favorite but who is, for all intents and purposes, a mere few hours old, a proper sendoff; pay homage to sixty years of adventures, across two eras of television; and tee up a bold new (Black, queer) incarnation of the Time Lord himself. As things go, it’s as busy and dizzy as any of showrunner Russell T. Davies’ usual finales, with all the messiness that entails.

Having freshly returned from the edge of the universe (as seen in “Wild Blue Yonder,” a show I was too busy to recap last week, sorry guys and dolls), The Doctor and Donna Noble (Catherine Tate) return to Earth to find it in a state of utter chaos. Turns out that, two days prior, everyone on Earth suddenly started thinking they were right, more so than usual. This self-righteousness turns pathological, even violent: Even the smallest disagreement turns into street riots and crashed airliners. It’s libertarianism gone mad!

Luckily, The Doctor and Donna are swept up by UNIT and brought to AvengersUNIT Tower by the returning Kate Stewart (Jemma Redgrave). (Don’t worry, Wilf is safe, though Bernard Cribbins’ illness and eventual passing prevented him from participating in this final special; that one scene we got at the end of “Yonder” is the last we’ll see of that beautiful man.) After a few brief re-introductions — Shirley from the first special’s here, and we even find room for Bonnie Langford as classic-Who companion Mel, who’s found herself a job at UNIT — the investigation races on to find a reason behind these sudden, inexplicable attacks.

The explanation, as we learn from some quick thinking via Donna (shades of her common-sense smarts from “The Sontaran Stratagem”), dates back to the invention of television itself: The first transmission of a televised image back in 1925, care of Scottish producer John Logie Baird and a stucco doll named Stooky Bill. Turns out someone, somewhere, embedded an arpeggio-like laugh — a giggle — in the first-ever image, which then spread out to every screen throughout history. And now, with a new South Korean satellite covering what few areas weren’t online, everyone in the world has the giggle in their brains. So off the Doc and Donna go in the TARDIS, racing back to Soho in 1925 to track down the culprit: A devilish trickster from the Doctor’s past known as The Toymaker (Neil Patrick Harris, his presence another indicator of the show’s big-budget pull and full-tilt catering to its queer audience).

Like many a Doctor Who special, “The Giggle” has a lot of ground to cover in a mere hour — almost too much to make its many spinning plates feel comprehensible. The terminally-online rage virus, the UNIT procedural drama, a pseudohistorical set in England, a psychological showdown with a reality-bending villain, all of these could be an episode on their own, steadily paced out over a single show’s entire runtime. But Davies and co. forced themselves to handle all of these stories at once, which means each of these ideas only gets a few minutes of purchase. To say nothing of the fact that this is a regeneration story (of sorts), one meant to say goodbye to a Doctor we’ve just gotten to meet again and to get used to a whole new one we’ll be following in the series to come.

Maybe the overstuffed nature of the episode is purposeful: In those few moments they’re not running from setpiece to setpiece, Donna notices the Doctor’s immense weariness. “You’re staggering along,” she remarks to him. “You’re wearing yourself out.” (She might as well have said, “Don’t you think he looks tired?”). It’s a uniquely Davies-ian wrinkle to the Time Lord, one he’s had ever since he revived the series in 2005: whether it’s the Time War, or every baddie he’s ever fought throughout the whole of time and space, or the hosts of companions he’s lost or abandoned throughout the years (as the Toymaker points out via a marionette show featuring Amy, Clara, Bill, and the Flux), the Doctor is a kind of Atlas, holding the universe on his oft-overdressed shoulders. It does feel strange to bring up this exhaustion now: it’s the crux of the Doctor’s character as long as we’ve known him in the modern era. He runs because he dares not look back, Puckish antics hiding a deep well of anguish.

But that’s the essence of the Russell T. Davies era, and it’s clear he wants to prove to viewers that this era of Who is back. It’s all big, Murray Gold musical flourishes, gurning speeches about the heights (or, in this case, depths — “Using your intelligence to be stupid”) of human potential, rousing emotional moments meant to usher us through all the nonsense on screen. From moment to moment, it’s exciting: Tennant and Tate still have tremendous chemistry — “I’m already running!” cries Donna as the two flee from the Toymaker’s collapsing shop — and Harris has a boatload of fun smirking his way through one over-amped accent after another. (Presumably, this is a way to offer an in-canon explanation for the…. err, problematic Asian affectations of Michael Gough’s previous take on the Toymaker during William Hartnell’s tenure.) Davies even offers a bit of glam-pop fun like he did in the old days, giving the Toymaker a suitably Master-y trot through UNIT headquarters to The Spice Girls’ “Spice Up Your Life,” Harris high-kicking his way through the room in a nutcracker outfit. (Don’t question it.)

All of this reflection on the Doctor (and the show’s) presumed exhaustion, however, seems purposeful to “The Giggle”‘s true utility: as a series finale of the old show, of sorts, and a true new direction for the series. That’s borne out in the Doctor and the Toymaker’s final confrontation on the helipad at UNIT Tower, where the latter zaps the former with a “galvanic beam” and forces him to regenerate. Only… in a typically magical Daviesian flourish, the Doctor bi-generates, with his next incarnation (Ncuti Gatwa) getting pulled out of him like the other half of a wishbone. Tennant’s still here, albeit with half his clothes; Ncuti inherits his shirt and tie, but little else, save for Fourteen’s tighty whities. (Does this mean Fourteen goes commando for the rest of this adventure?) And, since two heads are better than one, they handily beat the Toymaker at the world’s oldest game: Catch.

But what to do with two Doctors? Well, this is where all that self-reflection on all the running he’s been doing catches up with him. Donna convinces Tennant to stay put for a while, rest, and spend some time just recuperating from his various traumas on Earth with Donna’s family. “The one adventure you’ve never had.” (Save for the 24 years he spent with River on Derillium just a few seasons ago, but never mind that.) So, Ncuti’s doc inherits the TARDIS — but not before giving Fourteen his own, thanks to the lingering “state of play” the Toymaker’s defeat allows them — and we’ll see him at Christmas.

It’s a nifty way to have your cake and eat it too: Don’t worry, Tennant fans, you don’t have to see him die again, and you get the sexy new Doc in the bargain! But for all the fist-pumping fanwankery of the choice, it rings a bit hollow. After all, Tennant’s gotten this kind of out before, the last time he was with Donna: a clone Ten got to live happily ever after with Rose Tyler in another dimension. Now, there’s a third Tennant out there, and this one still has a TARDIS! Doctor Who has always been about change, about regeneration: here, no sacrifice has to be made, nothing meaningful is given up. The new Doc we’re about to follow is basically a blank slate, cured of all his pain and anguish by “doing rehab out of order.”

On the one hand, that’s exciting: What we’ve seen of Ncuti is invigorating, a slyer, sexier take on the Doc than we’ve seen before. (There’s a good reason Davies had him in Risky Business cosplay for his first few minutes of life: the man is gorgeous, and between calling people ‘honey’ and the implication his new companion will meet him dancing in a Scottish nightclub, he’s likely to be our sluttiest Time Lord yet.) But I also worry we’re losing something by making him no longer the last of the Time Lords, or even the last one of himself puttering around the universe.

Another thing to consider is that “The Giggle” isn’t just setting up the new era of Doctor Who, but an entire Whoniverse set to premiere on Disney+. There are hosts of spinoffs being teased here: the Doctor-Donna set of Noble adventures, maybe with a Mel, Kate and UNIT chaser, and so on. The Toymaker teases the return of the Master — previously locked in his gold tooth, which is then recovered by a nail-polished hand after his defeat, similar to the end of Series 3 — and another villain, “the one who waits,” who even terrifies the Toymaker. That could be exciting for diehard Who fans, but considering the oversaturation problems Disney has built up with Marvel and Star Wars, it’s worth greeting this news with a bit of caution.

Until then, “The Giggle” serves nicely, if busily, as the pivot point from old-new-Who to new-new-Who. These three specials offered a welcome return to form for a show that had lost its way for several years, giving longtime fans a reprise of their favorite Doctor-companion team to reset the board. Now the pieces are properly reshuffled, the fresh new face is set up for success, and the spinoff shows can help the brand lean on nostalgia as needs be. (Hopefully, Ncuti’s turn at bat won’t require or suffer from it.)

Doctor Who, “The Giggle” Trailer: