Schwarzenegger plays a suburban San Francisco family man who comes home one day to discover he has been illegally cloned — the clone has stolen his life and is living in his home with his wife and family.
But the cloners — portrayed as the very bad guys in the action-thriller — have failed to kill off the original, which means both the clone and the scientists spend the film trying to avoid the original Arnold's wrath.
In reality, modern science cannot yet clone a human being, but the movie scares up some provocative issues about technology that could be just around the corner.
"Cloning has progressed so fast that now we are at a point that the cloning of organs and the cloning of pets are going on in reality," Schwarzenegger said. "I think we ought to get involved in it, and study it carefully for what can be the benefits and disadvantages of it — rather than ignoring it and having another country doing it and bringing it to the United States," he said.
But for an actor who works in the rough-and-tumble action adventure genre, having a clone on the set could have its advantages.
"Now you're talking," said Schwarzenegger, who is no stranger to dangerous and demanding stunt work in films like the Terminator series, Total Recall and True Lies. "Here's an idea — let the other Arnold go off and do the stunts while I'm asleep in my bed. It would be easy," he said.
Considering the boon that just one Arnold can be at the box office, Columbia Pictures is betting that two Arnolds will draw double duty at theaters.
Fox News' Juliet Huddy contributed to this report.