LOS ANGELES – Arnold Schwarzenegger's Series 800 Model 101 Infiltrator was the perfect killing machine inflicted upon L.A. in 1984's "The Terminator."

But Schwarzenegger truly became the Terminator an hour into the classic movie that celebrates its 35th anniversary this week, when he unforgettably donned his curved Gargoyle wraparound sunglasses.

"The way he put those sunglasses on, it was powerful," Schwarzenegger says of his famed character. "They were these wraparound sunglasses, really interesting, and they became really big and really hip after that."

"That was a huge moment for Arnold, becoming the faceless killer," says director Tim Miller, who brings Schwarzenegger back for the franchise's sixth film, "Terminator: Dark Fate" (in theaters Friday), produced by original "Terminator" filmmaker James Cameron. "It’s a very monkey-brain response, when you can’t see people’s eyes, you're unsure about them and their motives."

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To state the obvious, people had every reason to be unsure of Schwarzenegger's motives in each of his film incarnations. In "The Terminator," he's the machine sent back in time by the world-dominating, super-intelligence force Skynet to kill Sarah Connor (Linda Hamilton), the future mother of revolutionary John Connor.

Shot in the eye, Schwarzenegger's machine shows a moment of vulnerability looking in the mirror, before plucking his eyeball out to reveal the machine's burning red lens. The sunglasses are functional, covering the robotic eye, and Terminator heads back to his killing work.

"The funny thing is, the red light still glows through the sunglasses," says Schwarzenegger, chuckling.

While the Terminator and his sunglasses were eventually destroyed, Schwarzenegger returned in 1991's "Terminator 2: Judgment Day" as a reprogrammed T-800 model. This time, he's a force for good, sent by the adult John Connor from the future to protect his younger self (and mother Sarah) from a new T-1000 Terminator.

Schwarzenegger's first order of "Terminator 2" business was procuring a motorcycle and clothes from a biker-bar customer, taking a pair of mirrored Persol Ratti sunglasses in the scene's final moment.

'He's going on a motorcycle, so he needs sunglasses," says Schwarzenegger. "He takes them, looks cool, and takes off."

Sunglasses are so tied to Terminator that Schwarzenegger was able to riff on the theme for laughs in 2005's "Terminator 3: Rise of the Machines." His Terminator takes an outfit from a male stripper and dons Elton John-esque star-shaped specs. These don't last long.

The allure of the sunglasses is so profound that Schwarzenegger, Cameron and Miller debated at length whether the star, now 72, would don them again in "Dark Fate." "We wanted to play with it," says Schwarzenegger.

One scene in the script featured Schwarzenegger, now a human-like machine called Carl who works with Sarah Connor, looking in the mirror, as he did in the original film. He then puts on a new pair of sunglasses.

"(Cameron) loves a good introspective look in the mirror to find the soul. He did it in 'T:1' and he did it here," says Miller. "That was in the script, that Arnold puts on the sunglasses, looks at himself, and walks to the car."

Miller shot the scene, but also shot scenes where Schwarzenegger looks in the mirror and decides not to put the dark glasses. "To put on those sunglasses meant the opposite of what we were trying to say," says Miller.

The director acknowledges that even his film editor, Julian Clarke, chose the sunglasses-wearing scenes initially.

"He told me, 'I just want to see him put the (expletive) sunglasses on and it’s a big audience moment, they are going to be excited about it,' " Miller recalls him saying.

We won't say which scene – sunglasses on or off – was ultimately chosen. But it's telling that a hardened Sarah Connor wears sunglasses for the bulk of "Dark Fate."

"Sarah is hiding behind sunglasses," Miller says, explaining how Connor has initially lost her humanity. "She’s a Terminator in the beginning of this movie."