Trivia

During the fight scenes, the camera often tracks Grey so that he remains in the middle of frame. According to director Leigh Whannell, this was achieved by hiding a phone somewhere on actor Logan Marshall-Green, which the cameras could then pair to and follow with as much accuracy as possible.

The company Cobolt is referenced throughout the film - a hi-tech military prosthetics firm which employed Asha and provided several of the advanced 'upgrades' used by the assassins, including optical implants. In Leigh Whannell's next film, El hombre invisible (2020), Cobolt is the hi-tech optics company founded by Cecilia's abusive ex Adrian Griffin. Since the two films are set several decades apart, it's likely that they're quietly set in a shared universe, and that both iterations of Cobolt are the same company at different times.

(at around 58 mins) At one point during the hacker building sequence, the Juego macabro (2004) doll can be seen painted on one of the walls. Leigh Whannell, the director for this movie, also wrote the first Juego macabro (2004) feature film screenplay.

Filming started in March 2017 in Leigh Whannell's hometown of Melbourne and lasted for 30 days.

(at around 58 mins) When Grey is entering the apartment block to find "Jamie", he pauses at some apartment buzzers. One of them says "J. Wan" - James Wan has been Leigh Whannell's main collaborator since the first Juego macabro (2004) film.