Gareth Edwards learned all his lines but Colin Baker hadn't had time, so he wrote out some of them on the TARDIS console as Jon Pertwee had - even joking "I did a Pertwee!".
Nicola Bryant was unable to reprise her role as Peri, as she was on holiday. Janet Fielding was brought in to reprise her role as Tegan.
Group Marshal Nathan and his subordinate, unnamed on-screen but referred to as "Turner" in the script, were a sly reference to John Nathan-Turner. This happened in rehearsal: the script called him Group Marshal Stern.
This was included as a special feature on the 2003 release of the Doctor Who DVD "The Two Doctors". However, following posthumous revelations that Savile was a child molester, later pressings do not include the sketch.