Candice Accola Candice Accola

 The Vampire Diaries' second season took a sharp turn when one of the show's innocent teens, Caroline (Candice Accola), became a vampire.  Executive producer Kevin Williamson says he never doubted which of the series' humans he wanted to take to the dark side.

"I said, 'We need a game-changer, and if one of these characters had to be a vampire, who would you want to see?'  I wanted to see Caroline," Williamson told TVGuide.com.

VIDEO: Will Vampire Diaries' Bonnie team up with Damon?

The main struggle Caroline faced as a vamp was whether she could stay with her human boyfriend, Matt (Zach Roerig). Surprisingly, Williamson says, the "stuck up, little narcissistic mean girl ... did the right thing."

But as Roerig says in the video below, Matt's not out of the woods just yet.  "Katherine is indeed the puppeteer in this show," he says about the most vicious vampire of them all. "And I'm proud to be a puppet in this next episode."