One part of the casting story deserves caution because decades of interviews have produced slightly different versions. Schwarzenegger has sometimes remembered the early discussion as though O. J. Simpson was essentially set to play the Terminator. Cameron’s account is firmer: Mike Medavoy suggested Simpson and Schwarzenegger as a pairing, Cameron rejected Simpson immediately, and the idea never became serious casting. Cameron has also said Schwarzenegger was never formally offered Reese by him. The most accurate description is therefore not that a completed casting deal was reversed at lunch. It was a studio-backed idea that Cameron expected to reject, followed by a meeting that revealed an entirely different use for Schwarzenegger. (Los Angeles Times)
The lunch itself is much better supported. Cameron remembers Schwarzenegger enthusiastically quoting Terminator scenes. Gale Anne Hurd remembered him being much more compelled by the machine than by Reese. Schwarzenegger remembers explaining behavioral rules that sounded almost like operating instructions. (BFI)
The Terminator should know its weapons so completely that it never needed to look at them. It should fire without blinking. It should not enjoy violence. It should not congratulate itself. It should not become emotional when something went wrong. It should simply continue toward the objective.
Cameron listened and realized that the man across the table was already thinking like the character.
That changed more than one role. If Schwarzenegger had played Reese, Cameron would have needed another Terminator. Michael Biehn would not have created the same vulnerable counterweight, and Schwarzenegger’s most recognizable screen identity might never have formed in the same way.