This is the second franchise that both Arnold SchwarzeneggerArnold Schwarzenegger and Christian BaleChristian Bale have both been involved in, without ever appearing together. They have both also appeared in the [Batman] films.
Josh BrolinJosh Brolin was asked to play Marcus Wright, but he turned it down.
In the original The Terminator Kyle Reese asks the police "What day is it? What year?" Marcus Wright asks the same thing of Kyle Reese at their first encounter.
At one point, the film carried the subtitle "The Future Begins." Coincidentally, the film Star Trek (which opened weeks before Terminator Salvation) used the same saying as a tagline. Actor Anton YelchinAnton Yelchin appears in both films.
After Claire DanesClaire Danes declined to reprise her role as Kate Brewster, Charlotte GainsbourgCharlotte Gainsbourg was once attached to star before pulling out due to a scheduling conflict with another film. She was replaced by Bryce Dallas HowardBryce Dallas Howard.
Old recordings of Sarah Connor are played in the film, with lines nearly word-for-word from The Terminator. Linda HamiltonLinda Hamilton voiced the lines herself in an uncredited role.
Director McGMcG asked the cast and crew to read the novel The Road by [?] Cormac McCarthy and Do Androids Dream of Electric Sheep? by Philip K. DickPhilip K. Dick - the basis for Blade Runner - because he wanted them to absorb the bleakness of the world in the novels.