The Sontaran costumes were cumbersome and limited the field of vision of the actors wearing them, so much so that they are often seen tripping through and over props. At one point, a Sontaran (played by the actor Stuart Fell) nearly takes a fall after missing a short jump and landing on a pool chair. As the aliens originate on a planet of notably high gravity, however, their clumsiness is easily explained.
An industrial strike, which was eventually resolved before production, forced the studio sets to be constructed within St Anne's Hospital in Redhill as the BBC's Christmas holiday specials were given priority in the regular studios. As a result of the industrial strike, Graham Williams was given the option of not producing the final six episodes of the season and have the money roll over into the next season. Williams rejected this because of the additional problem of inflation that year and didn't want the budgeted money to depreciate even further.
The outtake of Stuart Fell almost falling into a swimming pool was kept.
One of the tools that Rodan uses to work on the TARDIS controls is called a finkel groober. In the book "Charlie and the Chocolate Factory" by Roald Dahl, Ficklegroup was a rival candy maker of Willy Wonka who sent spies into Wonka's factory to steal his recipes.
This episode was watched by 10.3 million viewers on its original transmission.