From his new hair to his undeniably hot bod, Zac Efron is addressing all the important topics!

ET caught up with the Extremely Wicked, Shockingly Evil and Vile actor and his co-star, Lily Collins, this week, where he revealed the inspiration behind the platinum blonde 'do he's been sporting in recent weeks.

The fans are loving it, but the real question is, is it here to stay?

"No, I mean, that would be so much work," Efron explained to ET's Deidre Behar, confirming that it's not for a role but because he "lost a bet with a friend. It's kind of a double dare sort of thing."

Efron admitted that he also had the color when he was a kid, growing up with music idols like Eminem.

"Eminem was cool when I was growing up. This is my Stan coming out," he explained, referencing the rapper's 2000 hit song that featured Dido.

Later in the interview, Efron also opened up about his recent workout with Nina Dobrev for his new YouTube series, Gym Time. The pals worked out with trainer Johnny Fontana, who showed the two how to get lower ab muscles like the ones Brad Pitt showcases in the 1999 film Fight Club.

"[My abs] are never going to be the quality of Brad Pitt's," Efron said. "Those changed the world. I'm not looking to -- don't even mess with that. They're humbly chilling exactly where they need to be. Humbly chill."

All jokes aside, Efron does a great job flexing his acting muscles as serial killer Ted Bundy in Extremely Wicked, Shockingly Evil and Vile. He credits Collins, who plays Bundy's girlfriend, Liz Kendall, for helping him "raise the bar."

"The first day of filming, I'll never forget," he recalled. "It's freezing cold in Kentucky ... I smell like a thrift shop because my clothes were all from the '60s and I was just getting used to walking in this style. I walk in and I know my lines, I'm ready for the day and it was the first warm-up scene, and Lily was ready to go right then at rehearsal, perfect. Gave a perfect performance on the rehearsal, and I literally walked outside and I almost had a mental breakdown."

"I was like, 'We didn't even get to rehearse and Lily is going for awards already?'" he continued. [She's] so good! And I just sat at home and said, 'Zac, you gotta be better, you gotta be better, how can you do it?' And I figured out how."

The Bundy biopic hits select theaters and begins streaming on Netflix on May 3. In the meantime, hear more on Efron in the video below.

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