Tegan's ball gown proved challenging for Janet Fielding, which led to her having a number of wardrobe malfunctions on the set. In one such moment, when Peter Davison saw that Fielding had accidentally exposed herself, he concluded a line by ad-libbing "Oh, and Tegan, put your boobs back in!"
Peter Davison, Janet Fielding and Mark Strickson all disliked the dynamic that had developed between the Doctor, Tegan and Turlough, with Davison wondering why the Doctor would want to travel with a pair that was often portrayed in such a disagreeable light. John Nathan-Turner accepted their criticism, and encouraged them to work together to improve the characterisation.
The last appearance of The White Guardian and The Black Guardian.
Peter Sallis was booked to play Captain Striker. Sallis did attend one day of rehearsal before a strike started and production dates were charged. Sallis was signed up to a Last of the Summer Wine (1973) special and so could not make the dates. So, Keith Barron was cast instead.