A plea for help reaches the Doctor via his psychic paper: “Please save me from the monsters.” The TARDIS follows the distress call to a tower block on modern-day Earth. There the Doctor meets Alex, a frustrated father whose son, George, is seemingly afraid of everything -- especially the cupboard in his bedroom. When the Doctor tries to help, he realises that something strange really is lurking in George's cupboard. And this mysterious force has already trapped Amy and Rory in a macabre dollhouse, where they're stalked by sinister toys who seek to transform intruders into more of their kind.

Between writing his second and third Doctor Who scripts -- 2006's The Idiot's Lantern and 2010's Victory Of The Daleks -- one of Mark Gatiss' projects was a three-part horror series for BBC Four entitled Crooked House, broadcast in December 2008. In the final episode, Gatiss took a traditional haunted house motif and applied it to an ordinary modern dwelling. Doctor Who executive producer Steven Moffat felt that the same basic idea would generate an interesting scenario for his show. In January 2010, while he and Gatiss were working on the first season of their co-creation, Sherlock, he invited Gatiss to develop the concept into a script for Season Thirty-Two.

Pondering what sort of mundane building could make an effective story setting, Gatiss hit on the notion of a hotel which was hosting a psychiatric conference, only for the patients' phobias to take physical form. However, this was very similar to Toby Whithouse's The God Complex, which was also being developed for Season Thirty-Two. Instead, Moffat suggested that the script should be set in an apartment complex, with Gatiss turning his attention to childhood -- rather than adult -- fears. The resulting adventure became known as “What Are Little Boys Made Of?” in reference to the well-known nineteenth-century nursery rhyme.

As a child, Mark Gatiss had been unnerved by toys and costumes which only roughly approximated the human form

The writing process gave Gatiss the opportunity to exorcise a number of his own anxieties. As a child, he had been unnerved by toys and costumes which only roughly approximated the human form. He had a particular loathing for Victorian-era china dolls, and this inspired the Peg Dolls as the monsters of the piece. Mrs Rossiter being sucked into a mound of garbage bags stemmed from Gatiss' worries that trash might be riddled with vermin. The landlord, Purcell, was inspired by a physical education teacher who had terrorised Gatiss in his youth.

At one point, it was thought that “What Are Little Boys Made Of?” might be double-banked with another story. This had been necessary in the past to ensure that there was time to record a Christmas special alongside the regular thirteen-episode run. As such, Gatiss' narrative was focussed squarely on the Doctor, with Amy and Rory kept largely off-screen after being drawn into George's dollhouse. In the end, however, these plans changed and Gatiss made Amy and Rory's exploits an important element of the adventure. One alteration made at a late stage was the elimination of a running gag about whether door-to-door God-botherers were really aliens in disguise.

As it entered production, “What Are Little Boys Made Of?” was intended to be the fourth episode of Season Thirty-Two. It was made as part of the first production block alongside the putative episode three, The Doctor's Wife, under the direction of Richard Clark. At this stage, the script still included a closing scene in which Amy paused before following the Doctor and Rory back to the TARDIS. She then experienced a vision of the “Eye-Patch Lady”, who would first be glimpsed in the season's second episode, Day Of The Moon. The mysterious figure opened a hatch through which she said, “Amy, I just thought you'd want to know -- she's doing fine. Rest now.” This was intended to foreshadow the events of episode seven, A Good Man Goes To War.

Clark's team spent the first week of filming at Pembroke House, the former St Winefride's Hospital in Cardiff. Work there spanned September 6th to 10th, and dealt with scenes in both Alex's and Purcell's apartments. Following the weekend, cast and crew travelled to Dyrham Park, a country house built in the late seventeenth century near Dyrham in Gloucestershire. From September 13th to 17th, it served as the interior of George's dollhouse. On the 18th, Waring House in the city of Bristol provided the exterior of Rowbarton House, the tower block where George and his family lived. Material in the elevator was also recorded there.

Sunday the 19th was a day off, after which more filming at Waring House took place on September 20th and 21st. The next two days were spent at Dragon Studios in Pencoed; the effects sequence of Purcell sinking into the floor was shot on the 22nd, followed by some inserts on the 23rd. The remainder of “What Are Little Boys Made Of?” was taped at Doctor Who's usual studio home in Upper Boat, starting with the opening TARDIS scene on October 1st, and then various pick-up shots on the 7th.

In editing, a scene was dropped in which the Doctor revealed that he had taken a photograph of Purcell wearing the doll's dress, which he used to blackmail the landlord into lowering the tenants' rent. It was also found that the Peg Dolls were appropriately creepy while stationary, but were less effective as they moved silently through the dollhouse. After initially suggesting that the monsters be accompanied by a menacing giggle, Moffat instead proposed that they should be heard to recite a sinister nursery rhyme in children's voices. Gatiss agreed to craft an appropriate lyric, which would allude to the season-long story arc surrounding the Doctor's apparent death in the season premiere, The Impossible Astronaut. It was recorded by young actresses Fern Duncan and Frances Encell in early January 2011. Moffat was so pleased with the result that he decided to omit dialogue originally spoken by the Peg Dolls in the voices of Mrs Rossiter and Purcell. Instead, only Duncan and Encell's contribution would be heard; the nursery rhyme also became a recurring motif in subsequent episodes.

Originally episode three, Night Terrors was shifted into the second part of the season as episode nine

In December, Moffat grew concerned that several of the stories earmarked for the first half of Season Thirty-Two -- which would air in Spring 2011, before a twelve-week break -- were too alike in tone and setting. As a result, the schedule was shuffled, with The Doctor's Wife becoming episode four, “What Are Little Boys Made Of?” shifted into the second part of the season as episode nine, and the original episode nine, The Curse Of The Black Spot, moved up to episode three. This meant that “What Are Little Boys Made Of?” needed a new concluding scene, since the mystery of Amy's visions would already be resolved. As such, the shot of the “Eyepatch Lady” -- due to be filmed on January 27th, 2011 at Upper Boat -- was no longer needed. Instead, the adventure would now end with a new TARDIS scene, recorded at Upper Boat on April 16th.

One additional change came early in 2011 when it was decided that “What Are Little Boys Made Of?” was too long to serve as an effective title. The adventure briefly became known as “House Call”, but Gatiss wanted something more atmospheric. At his suggestion, the story was retitled Night Terrors. It was broadcast on September 3rd, at the slightly earlier time of 7.00pm. Its lead-in on this occasion was the second of two special editions of Total Wipeout.

• Doctor Who Magazine Special Edition #30, 21st March 2012, “Night Terrors” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #68, 2017, “Story 220: Night Terrors”, edited by Mark Wright, Hachette Partworks Ltd.