Arnold Schwarzenegger as the Terminator. Robert Patrick as the T-1000. Pretty iconic roles, right? But it was almost a robot from another android movie and a rock star as those unstoppable killing machines.

“They were thinking of Lance Henriksen for the Terminator, and they wanted Arnold for the Michael Biehn part of Kyle Reese,” revealed “Terminator” stunt coordinator Joel Kramer. “And Robert Patrick wasn’t James Cameron’s first pick – Billy Idol was.”

It’s more well known that Henricksen, who was the android Bishop in Cameron’s “Aliens” movies, was first choice for the Terminator – but Billy Idol? “That’s something most people don’t know,” said Kramer, who now works on the television spin-off, “Terminator: The Sarah Connor Chronicles.” “I don’t think I even told them that here, to be honest with you.”

But back when Cameron was figuring out what he wanted for the first “Terminator” sequel, Kramer walked into his office to look at the storyboards. “I was like, ‘Jim, these storyboards look just like Billy Idol!’” Kramer recalled. “And he was like, ‘Yeah, he was my first pick.’ But Billy had gotten into a motorcycle accident and broke his leg, so it didn’t work out, because he would have to be in lean running shape.”

Later on, Kramer asked Schwarzenegger what he thought about the might-have-beens, especially for his own part, and Arnold laughed. “He said it was a good thing, because there was so much dialogue,” Kramer said. “He said, ‘I would have f---ed that up totally.’ He had a great sense of humor about it.”

Even if Billy Idol couldn’t be a T-1000, another rock star has taken up the mantle, now that Shirley Manson from Garbage is a T-1001 on the television show. “She’s the same liquid metal model, basically,” Kramer said. “She can morph into whatever she wants, to a point. Any inanimate object as long as there are no moving parts.”

And Shirley welcomes more rock stars into the fold. Who should be the next in the line of T-1000s? With no hesitation, she offers up this possibility -- James Hetfield. Hey, at least he’s already metal.

Would "Terminator" have worked with these alternate casting choices? Who would you want to see be a Terminator in the next movie or television show? What do you think of Shirley Manson's take on the T-1000s?