- Creator Backlash: Peter Davison and Eric Saward both criticised the slowness of this serial on the DVD Commentary, arguing that the story could have been concluded in half the time.
- Creator's Favourite Episode: The cast cited this as a favourite. Peter Davison went so far as to say that the script finally "got hold of how I saw the part of the Doctor". Mark Strickson thought it was "clever and frightening" and gave him a chance to do some real acting.
- Deleted Scene:
- The first episode badly overran, forcing Ron Jones to make a number of trims. Much of the excised material involved Cockerill and explored his deepening sense of rebellion. Also cut was a scene in which Tegan and Turlough return to the TARDIS and find it surrounded by curious colonists; this is why Turlough later quips that the time travellers have lost their "news value".
- A cut scene in the third episode revealed that the voices of the Doctor and Tegan have echoed through the Tractators' tunnels, explaining how the Gravis is aware of the Doctor's intelligence.
- Inspiration for the Work: The Tractators were inspired by the wood lice which had infested a former residence of Christopher H. Bidmead's.
- Prop Recycling: The helmets of the Frontios security forces are the helmets of Federation troops from Blake's 7.
- Troubled Production: This story has a sad air hanging over its production with the deaths of two people involved before going before the cameras.
- Production designer Barrie Robbins killed himself after having done much of the preparation work and was replaced by David Buckingham.
- The role of Range was originally given to Peter Arne, but he was murdered in his own home the crime remains unsolved; although the prime suspect (a student Arne was in a relationship with) was later found dead in the Thames, it's not clear what the motive was. William Lucas was cast to replace him.
- The Tractator costumes proved overly constrictive and badly ventilated, requiring rewrites for the former and air to be pumped in during recording breaks for the latter.
- What Could Have Been:
- It was originally intended that Tractator technology should incorporate human remains, but this was deemed too gruesome. This idea was taken up in "The Girl in the Fireplace".
- Jim Broadbent and Donald Sumpter were considered for Cockerill.
- The producers intended to remove the TARDIS from the show completely and create the impression that the Doctor and his companions were stuck at the end of the universe. After the Gravis repaired the TARDIS in part four, the idea of removing the TARDIS from the show was scrapped.
- Working Title: The Wanderers.
Trivia / Doctor Who S21 E3 "Frontios"