"The Giggle" is the third and final of the 60th anniversary specials of the British science fiction television programme Doctor Who, written by Russell T Davies, directed by Chanya Button and broadcast in the United Kingdom on BBC One on 9 December 2023. It features the final regular appearances of David Tennant as the Fourteenth Doctor and Catherine Tate as Donna Noble, introduces Ncuti Gatwa as the Fifteenth Doctor and guest stars Neil Patrick Harris as the Toymaker, a character last seen in The Celestial Toymaker (1966). The episode also features the return of Jemma Redgrave and Bonnie Langford as UNIT commander Kate Lethbridge-Stewart and Mel Bush, respectively.

Set directly after the events of "Wild Blue Yonder", the episode sees the Doctor, Donna and UNIT confronting the return of the Doctor's old enemy, the Toymaker, who is behind a series of signals in a form of a "giggle" being transmitted, causing the human race to go insane over their opinions.

The episode was watched by 6.85 million viewers and received positive reviews from critics, who praised Harris’s performance and the writing, though the episode's "bi-generation" was met with a polarized response.

The Doctor and Donna are taken by UNIT to its headquarters, as the world's population has become inexplicably violent. The Doctor is reunited with Shirley, head of UNIT Kate Lethbridge-Stewart, and former companion and friend Melanie Bush. The Doctor determines the cause of the violence is a giggle from a Stooky Bill film from 1925, which John Logie Baird had recorded to demonstrate his invention, television.

The Doctor and Donna travel to 1925 and discover that the Toymaker had sold Stooky Bill to Baird's assistant. The Toymaker traps the two in his domain and reveals that he transmitted the signal to make humanity play a never-ending game of debate, by making them aggressively convinced of the absolute correctness of all their beliefs. The Doctor and the Toymaker play a game of cards, with the latter winning. However, the Doctor states that since he won the game at their last meeting, they are tied. The Toymaker resolves to have one final game with him and transports himself to the present day, with the Doctor and Donna in pursuit.

The Toymaker attacks UNIT before taking control of a graviton beam cannon. He reasons that since he faced separate incarnations of the Doctor for each game, he must face another, and uses the beam to mortally injure the Doctor, triggering his regeneration. However, to everyone's surprise, the Doctor instead splits into two incarnations via "bi-generation". Both the Fourteenth and Fifteenth Doctors challenge the Toymaker to a basic game of catch. The Doctors emerge victorious, and the Toymaker is banished from existence.

Aboard the TARDIS, the Fifteenth Doctor advises his predecessor that he needs to recover from the extensive traumas that his past incarnations have accumulated across their lives. Donna suggests to the Fourteenth Doctor that his old face returned because he is emotionally exhausted and has subconsciously recognised this need. She invites him to consider retiring from travelling and staying with her and her family, but he is reluctant to leave the TARDIS behind. The Fifteenth Doctor, realising that the Toymaker's rules of play still apply – when one wins a contest, one gets a prize – uses a mallet from within the TARDIS to create a second identical TARDIS, in which he departs after a cheerful farewell. The Fourteenth Doctor settles down with Donna and her family, while the Fifteenth Doctor travels the universe in his predecessor's place.

Prior to the episode airing, several details about the sixtieth anniversary specials were leaked, including the bi-generation twist. Davies was unconcerned, believing that the general public likely wouldn't know about the leaks.

Davies was inspired to include Stooky Bill within the episode after recently working on the biographical TV series Nolly. This caused Davies to look into puppets and puppeteers, with the idea of someone pulling the strings, which inspired Davies to use The Toymaker as the antagonist. Davies also wished to bring back the Toymaker due to the antagonist last appearing in the 1960s, with "The Giggle" itself being the show's sixtieth anniversary, stating that "all the sixties came together, and there he was." The Toymaker utilizes various different accents throughout the episode, which Davies explained was due to the fact that the Toymaker used stereotypical Chinese elements in the character's original appearance. Davies stated that he did not wish to "whitewash" the Toymaker, and thus expanded on the concept by having the Toymaker "playing with race" as a weapon in order to make the Toymaker a fundamentally evil character, without ignoring racist caricatures present in the Toymaker's original serial.

Chanya Button directed the episode. Filming for the specials commenced in May 2022, and wrapped at the end of July 2022. The initial scenes, in which the city erupts into chaos and the Doctor dances with the Toymaker, were filmed in Old City, Bristol, with Bristol's film office assisting in production of the scenes. To celebrate the occasion, Bristol's film office produced a map depicting every filming location in Bristol used throughout Doctor Who's run by that point.

The UNIT Headquarters set utilized a ramp, which was constructed to be wheelchair accessible. The TARDIS similarly gained a wheelchair accessibility ramp in the episode, which was the result of Davies receiving a letter from a fan who stated they wouldn't have been able to enter the TARDIS due to their wheelchair.

One scene in the episode depicts the Doctor encountering life-sized marionettes resembling himself and Baird's assistant. Puppeteer Brian Fisher puppeteered the marionette alongside multiple other people, with the marionette requiring three to four people in order to properly puppeteer. The actors would film their parts, and the production team would overlay the actors on top of the puppet, which was filmed separately. Harris had experience puppeteering, and puppeteered the puppets himself in a scene in which the Toymaker taunts the Doctor. He talked to the team handling the puppets and worked out how best to handle the puppets for the scene, which was filmed in only half a day. After this, the team went and filmed the close-ups for the puppets, mimicking how Harris filmed them previously. The puppets resemble three of the Doctor's past companions: Amy Pond, Clara Oswald and Bill Potts, all of whom he met after leaving Donna behind in "Journey's End" (2008), with all three having died in the universe's canon.

The Toymaker uses several costumes in the episode, which were constructed by costume designer Pam Downes and members of the costumes team. In one scene, the Toymaker attacks UNIT Headquarters while dancing to the song "Spice Up Your Life" (1997) by the Spice Girls. In this scene, Harris wears a band leader outfit. Downes wished to use boots with red laces to highlight the red of the costume, and thus used women's riding boots to accomplish the outfit. For the musical number scene, Harris did choreography training alongside the other actors, including Jemma Redgrave. Harris additionally had to wear specially molded teeth for the episode in order to depict the Toymaker as having more teeth than he should.

The bi-generation scene was filmed with a special craned camera, which allowed for the team to overlay Tennant and Gatwa's parts of the bi-generation onto each other. To simulate a split, Tennant and Gatwa split half of Tennant's costume between themselves. Due to Tennant filming first, he got to select which parts of the outfit he wore, while Gatwa was left with the remaining parts. The initial visual effect for the split was considered too violent by Davies and producer Phil Collinson, and it was toned down for the final episode. The Toymaker's catch scene was filmed with many individual single shots, with each one focusing on one of Tennant, Gatwa, and Harris. Various different cameras were used to film the scene, including drones. The three actors would hide the ball behind the palm of their hand and mimic catching the ball, in part due to difficulties catching the balls by the actors.