"The Giggle" is the third and final of the 2023 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 majority of the human race to go mad over their beliefs.

The episode was watched by 6.85 million viewers and received positive reviews from critics, who praised Harris' performance and the writing.

The Doctor and Donna are taken by UNIT to its headquarters, as the world's population has gone 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 video 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 he transmitted the signal to make humanity play a never-ending game of debate, by making all of their opinions supreme and causing them to go violent if they're proven wrong. 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.^{[lower-alpha 1]} 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 laser cannon. He reasons that since he faced separate incarnations of the Doctor for each game, he must face another, and mortally injures the Doctor with the beam, triggering his regeneration. However, to everyone's surprise, the Doctor instead splits into two incarnations via "bigeneration". 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 and sealed in a box, which is then confiscated by UNIT.

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 recognized this need. She invites him to consider retiring from travelling and staying with her and her family, but he admits 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.

David Tennant and Catherine Tate returned to the series as part of the 60th anniversary specials.^[2] Tennant stars as the Fourteenth Doctor while Tate reprised her role as Donna Noble.^[3] Ncuti Gatwa made his first appearance as the Fifteenth Doctor. Neil Patrick Harris portrayed the Toymaker, a character last seen in The Celestial Toymaker (1966), then portrayed by Michael Gough.^[4][5] Chanya Button directed the episode.^[6] Filming for the specials commenced in May 2022, and wrapped at the end of July 2022.^[7] Due to failing health, Bernard Cribbins' role as Wilfred Mott was reduced, however, he was able to film one last appearance for the ending of "Wild Blue Yonder", his final performance before his death on 27 July 2022, one day after production for the specials wrapped.^[8][9] An uncredited double stood in as Wilfred for "The Giggle", which featured usage of an archival audio recording of Cribbins from "The Poison Sky" (2008).^[10]

The episode features the return of Jemma Redgrave's Kate Lethbridge-Stewart, last seen in "The Zygon Inversion" (2015) and Bonnie Langford's Mel Bush who made her last major appearances in Dragonfire (1987).^{[lower-alpha 2][11]}

"The Giggle", along with the other two specials "Wild Blue Yonder" and "The Star Beast", were released together on DVD and Blu-ray on 18 December 2023 as part of the "60th anniversary collection".^[30]