"Terminator: Genisys" is in theaters July 1.

When it comes out, one of the most talked about scenes will be a fight that occurs early on in the film between Arnold Schwarzenegger's Terminator character fighting a younger version of himself from the original 1984 film.

It's been heavily marketed in ads for the movie.

It was also the most difficult scene to make, according to the film's screenwriters.

Without giving too much away, the film recreates a few of the original scenes from 1984's "Terminator." The filmmakers weren't able to use scenes from the original film since they didn't have the rights to the movie.

"Because the first movie is owned by one entity, Hemdale and Orion, and the second movie was owned by another entity, and the third movie another one, and then got bankrupt and sold it to David and Megan Ellison and they made the fifth movie," Schwarzenegger explained to a crowd at a Q&A after a fan screening of the film. "Therefore it was impossible for them to go and to take the scene from the 1984 movie and then put that in a movie and then continue on from there." 

"Genisys" wouldn't have come together without 28-year-old model and bodybuilder Brett Azar who had to fight Schwarzenegger on set of the film in the nude.

Here's Azar, who's credited with playing the "Young Terminator" in the film.

Azad says Schwarzenegger has been his idol since elementary school. 

For filming, Azar wore a wig to capture the look of Arnold on screen.

He also had to get dozens of ink dots drawn onto his face to help get the digital placement of Schwarzenegger's younger face onto his just right. Azar told The Terminator Fans blog it took at least an hour to do each day.

Azar told the Terminator Fans blog he had to be completely nude to film the scene with Schwarzenegger, covered only by a sock.

Jai [Courtney] got to wear a triangle piece that was more like a g-string. I had literally a sock/pantyhose with a drawstring. … yeah nothing was concealed. And I had to run at Arnold full speed, grapple with him, throw kicks and punches, approach him on the ground…. just hanging out. I really didn’t care though. I was living my dream and it didn’t matter if I was naked doing it. The stunt guys always made a good joke of it though… leaving a plate of cucumber slices and a sausage in a specific arrangement in my trailer…. I just know I’ll never feel awkward again in my life.

Azar doesn't only fill in for the younger, villainous version of Arnold. He also fills in as the body double of the younger version of Arnold who is seen with a young Sarah Conner in trailers for the film. 

Here's an image of him filming the scene.

The 6'2" Azar weighed 250 lbs while filming. He shows off the secret to staying fit for "Terminator Genisys": "scivation xtend bcaas 7 scoops every day in my gallon... 49grams a day... terminator secret ;)"

You can read his full interview here. 

More "Terminator": Arnold Schwarzenegger fought with James Cameron over one deleted scene in "Terminator 2"

SEE ALSO: Our review of "Terminator Genisys"

AND: Arnold Schwarzenegger: The majority of people in Hollywood said I'd never make it as an actor

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