- Creator's Favourite: Jon Pertwee named the Draconians as his favourite monster, largely because of how expressionate they were and thus easier to act alongside than Daleks.
- Deleted Scene:
- During editing, the first scene of Episode Three, following the reprise, was drastically cut down for timing reasons: a key background scene was eliminated and the character of Sheila, assistant to the President of Earth, was reduced to merely that of a walk-on who massaged the President whilst she talked to her secretary. In the complete version of the scene, Sheila had discussed the origins of the tensions between Earth and Draconia with the President, during which it was revealed that the young General Williams had destroyed a Draconian battle-cruiser not realising that it was unarmed, and merely being used to transport the Draconian envoy in a blast from his own spacecraft's exhaust rockets. Luan Peters (Sheila) retained an on-screen credit despite no longer having any lines.
- During the scene in the President of Earth's office in Episode Six, where the Doctor, the President and the Draconian prince are seen watching on a large wall-mounted video screen a news film report of Congressman Brook at a rally calling for war with Draconia, Bill Mitchell was originally to have featured as a newscaster, announcing the news of the rally and introducing the film report. Unfortunately, either due to the episode over-running or a decision by Paul Bernard to use only the footage of Congressman Brook, his appearance was edited out of the finished programme. This decision would appear to have been made at a late stage, which explains why Mitchell is still credited both on-screen and in Radio Times.
- Prop Recycling: The same three Dalek casings used for "Day of the Daleks" appeared in Episode Six.
- What Could Have Been:
- Malcolm Hulke intended the Draconians to be like the post-Napoleonic Hapsburgs, although their eventual execution was more akin to a Japanese shogunate.
- The original outline had the Cybermen working with the Master, but they were swapped for the Ogrons before scripting started.
- The human president was originally a man.
- The Doctor's discovery that the attacks in space were being committed by Ogrons initially came much later, after the Master had liberated him from prison.
- At the lunar penal colony, Patel was originally called Doughty.
- The final sequence in the Master's headquarters was intended to contain the giant Ogron-eating monster, but director Paul Bernard did not like the costume and omitted it, leaving the scene with just frightened Ogrons running away from something unseen. Barry Letts and Terrance Dicks felt the sequence lacked impact and a new ending was filmed in the TARDIS as part of the first production block of the following story, "Planet of the Daleks". Unfortunately, Roger Delgado was not available to take part in the new ending, meaning that he abruptly disappears in the middle of the last scene, and this ultimately proved his last appearance as the Master before his tragic death later that year.
- You Look Familiar: John Woodnutt (Draconian Emperor) had previously played Hibbert.
- You Sound Familiar: When the Doctor uses the stolen hypnosound to appear as a Dalek to the Ogron guard in Episode Six, his commands are provided by Dalek voice actor Michael Wisher.
Trivia / Doctor Who S10 E3 "Frontier in Space"