This story is significantly more comedic than the previous Dalek stories and many that followed. Much of the humour was added by story editor Dennis Spooner.
The Beatles appear in this episode via footage from Top of the Pops (1964) playing Ticket to Ride. The band were originally planned to appear as old men performing in the 21st century but this proposal was vetoed by their manager Brian Epstein.
This serial was earmarked to form the basis for a third "Dr. Who" film starring Peter Cushing, to follow Daleks' Invasion Earth 2150 A.D. (1966), but the film was never made.
Terry Nation discarded several ideas for the serial, including sequences set in ancient Egypt (where the first of the Great Pyramids would be erected over the remnants of a destroyed Dalek), the planet Stygian whose inhabitants were invisible, and the mist-shrouded world of Vapuron. These ideas would subsequently be recycled in The Daleks' Master Plan.
The story was commissioned at late notice when another of Terry Nation's stories fell through. It is believed that the slot was originally to be filled by his planned historical The Red Fort.