Jacqueline Hill (Lexa) returns to the Doctor Who series fifteen years after last in the Tardis, as Barbara Wright (one of the original companions).
This story features the only use in Doctor Who of a camera-linking system known as Scene-Sync that allowed the use of non-static shots of characters superimposed onto a miniature set. As the cameras on the actors were moved, the cameras on the miniature set moved the equivalent scaled amount automatically. The exact scale motion was achieved by trial and error, involving minute adjustments to the voltage delivered to the slave camera's motors.
During production of this story, Madame Tussauds in London debuted the "Doctor Who Exhibition". Included were sculptures of both the Fourth Doctor and his Meglos doppelganger. As a result, Tom Baker is the only person to have appeared twice in the wax museum.
Brotadac is an anagram of 'bad actor'. This was a joke by the writers.
Jacqueline Hill came to be cast because Terence Dudley was friends with her husband Alvin Rakoff. John Nathan-Turner approved of her casting.