The working title for this story was The Six Doctors.[3] It would have been written by former script editor Robert Holmes and would have featured the Cybermen and their kidnapping of the five incarnations of the Doctor; in their attempt to extract Time Lord DNA to turn themselves into “Cyberlords”, the twist being that the First Doctor and Susan would actually be android impostors[3] (the former being the “Sixth Doctor” of the title) and the Second Doctor would have saved the day. However, Holmes dropped out at an early stage and another former script editor, Terrance Dicks, was brought in instead. Some elements of this plotline would be reused in Holmes’ own The Two Doctors (1985) and in Chris Chibnall’s The Timeless Children (2020).

The programme is officially a co-production with the Australian Broadcasting Corporation, although the production team were not aware of this during production and the agreement in effect amounted to little more than a pre-production purchase pact. Nathan-Turner’s first choice of director for the story was Waris Hussein, who had directed the first-ever Doctor Who serial, An Unearthly Child, in 1963. However, Hussein was in America at the time and was unable to accept the offer.[4] Nathan-Turner then asked another veteran director, Douglas Camfield, to direct but he also declined.[5] Camfield was also very ill with heart disease, and this may have affected his decision not to direct the production. He died of a heart attack early in 1984.[6]

The original script featured an appearance by the Autons, last seen in Terror of the Autons (1971). After being dropped into the Death Zone, Sarah would have been attacked by a group of them before being rescued by the Third Doctor. However, due to budgetary restrictions, the scene was dropped[7] and replaced in the finished version. Just before she meets the Third Doctor, Sarah falls a few feet down what fans have generally considered a rather unconvincing slope. In the novelisation, Sarah actually steps off a cliff. This was what was originally intended in the script, but for budgetary reasons the sequence was changed.

Location filming took place at Cwm Bychan, Llanbedr.[8] The Yeti costume used in the serial was last used in The Web of Fear in 1968. It had decayed badly in 15 years of storage, requiring dim lighting and selective camera angles during filming.[9]

In the various publicity photos of the five Doctors from this story, a waxwork model of Tom Baker from a 1980 Doctor Who Exhibition in Madame Tussauds was used. According to producer John Nathan-Turner, Baker had agreed to do the photocall for the 20th anniversary but, suspecting that he might not turn up, Nathan-Turner arranged for the waxwork to be on location.[10]

The end credits featured a specially-mixed version of the theme music, which began with Delia Derbyshire’s original 1960s arrangement and then segued into the Peter Howell arrangement being used by the series at the time (the former being played at a slightly higher speed to match the tempo and pitch of the latter). This arrangement was only used on this one occasion[11] and was the last time that the Derbyshire version was heard during the show’s original run. A unique arrangement of the opening credits music was also used, which ended in a brief coda phrase that was never used in any other serial.

The First Doctor was played by Richard Hurndall, replacing William Hartnell, who died in 1975. Hartnell does make an appearance, however, in a pre-titles clip taken from the end of The Dalek Invasion of Earth (1964).[11] After initially agreeing to take part, Tom Baker declined to return so soon after his departure from the series two years before, saying in 2014, “I didn’t want to play 20 per cent of the part. I didn’t fancy being a feed for other Doctors—in fact, it filled me with horror.”[12] His appearance was pieced together with footage from the unaired serial Shada.[13]

In early drafts of the script, some of the Doctor and companion combinations were different. Originally, the Fourth Doctor would have been paired with Sarah Jane Smith, the Third Doctor with Brigadier Lethbridge-Stewart and the Second Doctor with Jamie McCrimmon.[14] When Frazer Hines, Jamie’s actor, proved unavailable for more than a cameo appearance the script had to be altered, pairing the Second Doctor with Victoria Waterfield. This was revised again when Deborah Watling, Victoria’s actress, became unavailable and Baker decided not to appear, resulting in the pairings as they were screened. Instead of meeting phantoms of Jamie and Zoe (Wendy Padbury), the Second Doctor and the Brigadier were originally scripted to meet Zoe and Victoria. The Doctor would have realised the truth about them when Victoria called Lethbridge-Stewart “Brigadier”, when she only knew him as a Colonel (in The Web of Fear). Deborah Watling was unable to make the recording dates but Frazer Hines was able to free himself up for a day’s shooting, so Jamie was written in instead.

John Levene was invited back as Sergeant Benton but objected to the script requiring Benton to not recognise the Second Doctor. Levene felt this was unfaithful to his character, who he felt would not forget the Second Doctor, and he declined to participate. The scene was filmed with a character introduced as Colonel Crichton in his place.[15]

In April 2013, Carole Ann Ford revealed the producer had initially insisted that Susan not refer to the Doctor as her grandfather: “You will not believe why. They said, ‘We don’t really want people to perceive him as having had sex with someone, to father a child.’ I just screamed with hysterical laughter and said, ‘In that case, I’m not doing it.'” The script was changed to include mentions of the characters’ relationship.[16] The Five Doctors was first broadcast in the United States on the actual date of the programme’s 20th anniversary. The broadcast in the United Kingdom was delayed two days so it could coincide with the BBC’s Children in Need charity night, with an outro in character by Peter Davison. There were a few segments in the BBC broadcast that had not been shown in the US airing.