The miniature shoot and the entire animation process had to be completed during the COVID-19 pandemic. Production moved much slower because of this.
In the script, Flash's car is referred to as "Fury". The only reference to this in the film is on the car's license plate.
Originally, Flash's car was going to be Scott Reacher's 1995 Mustang. The car broke down several months before the script was even written. The crew opted to use a miniature 1969 Dodge Charger instead. Four variations of the miniature were used.
The film's original score was completed in 24 hours.
Flash was originally designed with a regular face with an off-blue tint to his skin. He was also going to wear sunglasses and a jacket. Tyler W. Moore suggested to either give the character a mask or skull face so he wouldn't just look like a blue Terminator.