According to The Hollywood Reporter, Christian Bale, who director McG had to convince to be in Terminator Salvation, ended up having to work with the director to rewrite the screenplay in order to accommodate the actor's burgeoning stardom.

Initially, McG wanted Bale to the play the role of Marcus Wright in the film. However Bale wanted to play the role of John Connor who had been a central character in the other Terminator movies. In the original drafts of Terminator Salvation Connor's role was smaller.

RELATED: Mechagodzilla in Godzilla Vs. Kong Was Inspired by the T-800 Terminator

The director reports that he and Bale "worked day and night" to rewrite the screenplay with Bale.

"A lot of the work was integrating (Connor) into scenes ... and having that feel integral and sensible, as opposed to grafted on just because there was a star in the part," stated John Brancato, the Terminator Salvation screenwriter.

Initially the character of Marcus Wright (played in the film by Sam Worthington) was an executed man who lends his body to science, and comes back to life when machines take over the world.

In the current film, both Wright and Connor get equal time on screen.

Terminator Salvation comes to theaters May 21 from Warner Bros. Pictures.