Trivia: For many years, it was thought that every episode of "The Daleks' Master Plan" had been destroyed by the BBC, in their 1970s purge of the archives. However, in 1983, two episodes (5 and 10) were found and returned to the BBC for preservation. They were found in a highly unlikely location: the basement of the Church of Jesus Christ of Latter Day Saints in Clapham, South London. No one knows how they got there.
Trivia: For the first three seasons of Doctor Who, each individual episode had a title, as well as an "umbrella" title for the whole story (like the titles of chapters in a book). This has caused much confusion over the years. For example, the story "100,000 BC" is the title of the first Doctor Who story, but this story is also widely known as "An Unearthly Child" after the title of the first episode. By the time of "The Gunfighters" (first broadcast in May 1966) this source of confusion was realised, and the practice ceased. From 28th May 1966, each Doctor Who story had just the "umbrella" title, followed by "Part One" "Part Two" and so on.
Trivia: A "missing, believed wiped" episode was found in January 2004, when "Day of Armageddon", the second episode of "The Daleks' Master Plan", was returned to the BBC by an employee of Yorkshire Television. He had rescued the print from destruction in the early 1970s when, as a young BBC engineer, he had found it in a room at the BBC's Ealing Film Studios, which he had been asked to clear of rubbish. He disobeyed the instruction to destroy the episode and took it home with him. Arguably, he stole it from the BBC, but if he hadn't, it would never have survived. In 2013 (I forgot the episode name, but it was the one with Salamander), they found the rest of the films for another episode. The new ones were animated, combined with the already existing ones and released on DVD.
Trivia: William Hartnell appears in the credits at the end of this Doctor Who story... despite the fact that he did not actually appear in this episode at any stage. He had a contract that he would be in the credits for all episodes, which ended after he left the show in "The Tenth Planet." Though he wasn't shown, he had to be credited.
Trivia: One of the episodes of this serial, "The Feast of Steven", was broadcast on Christmas Day, 1965, making it the show's first technical Christmas special. Due to expectations of low viewer numbers on the holiday, the episode was made as a humourous romp through 1920s Hollywood, with no connection to the plot of the rest of the serial and the Doctor breaking the fourth wall at the end to wish the viewers a merry Christmas. This is one of two episodes known for certain to be completely lost, having been wiped in the BBC's archive purges.