The scene where an Auton is hit with a car and tumbles off a cliff, was quite real. Dinny Powell was driving the vehicle in place of Richard Franklin, and stuntman Terry Walsh, as the Auton, fell further down the slope than intended, being injured in the mishap. He nevertheless got back to his feet in the same take as planned.
The Auton invasion was much different in the original script. The daffodils (and the troll dolls) would be animated when the temperature reached a certain level - a level which would be obtained thanks to a fortuitous oncoming heat wave in Britain. Terrance Dicks felt this was illogical, as it would make more sense for the Master to carry out his plan in a tropical locale. It was decided to replace this with a broadcast activation signal.
This episode was watched by 8.1 million viewers on its original transmission.
In the original script, it was The Brigadier, rather than The Doctor, who was attacked by the phone chords.