Caity Lotz performed all her own stunts for the movie.
The Machines speaks Persian/Farsi, Iranian language.
Costume designer Chrissie Pegg was given just two weeks to make 100 costumes with only £40 for each and had only one assistant.
In the opening scene, the test to determine where the soldier thinks Lucy (Siwan Morris) may have hidden the tennis ball is a variation of the Sally-Anne "False-Belief" test often used to determine "theory of mind" or, the ability to empathize, in psychological tests designed to determine the presence of Autism Spectrum Disorder.
The "Military Base" scenes were filmed at Greenham Common, United Kingdom.