- Corpsing: Janet Fielding and Sarah Sutton suffered an attack of the giggles while they were filming the final scene, in which their characters were supposed to be grieving for Adric. Fortunately, they eventually managed to regain their composure, enabling the scene to be filmed; the incident is recounted in the "making of" documentary on the DVD.
- Creator Backlash: While his overall opinion of the story was quite positive despite its notoriously unforgiving shooting schedule, director Peter Grimwade absolutely hated Malcolm Clarke's incidental score for the serial, and tried to get Peter Howell, whom Grimwade had worked with on "Kinda" earlier that season, to provide a replacement. Howell wasn't available, however, resulting in the story retaining Clarke's score.
- Creator's Favourite Episode: This was a favourite story among the cast.
- Enforced Method Acting: Janet Fielding let out a real scream when the dying Cyber Leader shoots the TARDIS console, as her hair was hit with sparks.
- Missing Episode: While reviewing the Doctor's history with the Cybermen, the Cyber Leader refers to the events of "The Tomb of the Cybermen", but the clip of Patrick Troughton comes from "The Wheel in Space". At that point, "The Tomb of the Cybermen" had not yet been returned from Hong Kong and was still missing from the BBC Archives.
- Prop Recycling: The Cyberscope prop was built using parts the modelmaker had scavenged from the Nostromo set constructed for Alien. Similarly, the digital readouts on the device flash up a random series of numbers which were also seen on the monitors of the Nostromo set.
- Stunt Casting: Beryl Reid as Ellen Ripley-esque space freighter captain, a role that was... not quite what you'd expect to see Beryl Reid playing.
- Uncredited Role: In addition to writing the story, Eric Saward also served as script editor. However, he went uncredited due to BBC guidelines preventing him from taking credit for more roles than what he had been assigned, and thus Antony Root, who previously acted as script editor for "Four to Doomsday" and Saward's earlier story "The Visitation", was credited for the position instead.
- What Could Have Been:
- The original serial for the slot was the wonderfully ambitious "The Enemy Within" by Christopher Priest (featuring the Doctor facing off with the TARDIS' power source, a tentacled Eldritch Abomination!) but an argument over re-write fees led to John Nathan-Turner rejecting it and Eric Saward had to write the serial to replace it. Traces of the danger-at-the-centre-of-the-TARDIS idea made it into "Castrovalva", where it was intended as foreshadowing of Priest's story to come.
- From the outset, John Nathan-Turner intended to bring back a recurring villain for the story, and the rest of the production team briefly considered the Daleks for this position. However, he was reluctant to use them, and consequently had them swapped out for the Cybermen, a personal favorite of writer Eric Saward. The Daleks would eventually get their clash against the Fifth Doctor in "Resurrection of the Daleks" (also written by Saward).
- There was some consideration of redesigning the Cybermen. Dinah Collin wanted to remove the handlebars on the Cybermen costumes, but Nathan-Turner vetoed that idea as he didn't want to lose the distinct iconography. (Plus fan consultant Ian Levine pointed out that only the Cyber-Controllers were meant to lack handles). Another idea was going to have some visible fluids in the tubes.
- Considered for Commander Scott were Colin Baker, Peter Firth, Martin Jarvis, Martin Shaw, Patrick Stewart and David Warner.
- Eric Saward considered having the Cyber-Leader survive the story, providing yet another sign of the Fifth Doctor's fallibility in comparison to his predecessor, but ultimately decided against it.
- Working Title: Sentinel.
Trivia / Doctor Who S19 E6 "Earthshock"