Trivia / Doctor Who S5 E4 "The Enemy of the World"
Absentee Actor: Jamie and Victoria are absent from the fourth episode, as Frazer Hines and Deborah Watling were on holiday.
Acting for Two: Patrick Troughton plays both Salamander and the Doctor for this adventure. Considering the only difference between them is a hair style and costume and accent, Patrick Troughton puts his heart into making those two completely different.
Author Existence Failure: David Whitaker was working on novelising his scripts at the time of his death in 1981. Ian Marter completed it.
What Could Have Been: The chase scene in the first episode originally took place in a crowded holiday resort. This was changed due to logistical difficulties.
Initially, it was planned that the Doctor and Salamander would meet more than once, but due to the technical complexity, there was eventually only the one confrontation scene, at the story's climax (utilising editing and a split-screen technique).