EXCLUSIVE: Derek Hough Talks Epic, Surprise 'AGT' Performance & How Julianne Is Getting 'Ripped' for New Film

Daniel Boczarski/Getty Images for National Park Foundation

The 32-year-old dancer says he was 'so nervous' to take the stage with Light Balance -- find out why!

Derek Hough is still raving over the season 12 finale of America's Got Talent!

ET joined the 32-year-old dancer on his visit to the Indiana Dunes National Lakeshore in Porter, Indiana, on Tuesday, in celebration of the National Park Foundation's "Find Your Park" initiative. During our interview, he opened up about his epic surprise performance with Light Balance and how it all came to be.

"When they [producers] asked me to be a part of the finale, I was like, 'Sure, but what do you have in mind?'" he explained. "They were like, 'There's this group, Light Balance.' I was like, 'Yeah, I've seen their stuff. It's amazing, incredible.' I learned that routine in an hour, the day before."

"I was super nervous!" he confessed. "I was nervous because, once you put all the stuff on, there's this thing where your eyes -- you can't really see anything properly. And then it's dark [onstage], you're moving around in the dark."

Hough continued on, telling ET that during rehearsals, he kept making mistakes by facing the wrong way.

"I was like, 'Oh my gosh. This is going to happen. I can't believe myself,'" he recalled. "But it was so much fun, really great. Good times."

After a massively successful first round, Hough was also ecstatic to talk about World of Dance getting picked up for a second season. He told us that he personally plans to do things a little differently as a judge the second time around, but has no doubt the show will continue to highlight even more incredible talent.

So, is there any possibility that Light Balance could be one of the acts on the WOD stage? Never say never!

"Oh my gosh!" he exclaimed. "That would be awesome. They were so awesome."

Moments before our interview, Hough's sister, Julianne, also announced some exciting news of her own via Instagram. The 29-year-old dancer has officially been cast to play the First Lady of Fitness, Betty Weider, in George Gallo's Bigger.

"I will say this, she has definitely been training and getting in shape for it," he revealed. "She's gotta be pretty ripped for that [role]."

"She was just telling me, she's trying to get that 'honeymoon weight' off," he continued. "Not like there's really much to get off -- I mean, have you seen her honeymoon photos? She has, like, an eight-pack goin' on. What is that? Just crazy."

During the trip, ET also chatted with Hough about his own passion projects, Dancing With the Stars, his relationship with Hayley Erbert and more. Stay tuned to ETonline.com for the full interview (pics included!) coming soon.

In the meantime, watch the video below to hear Hough explain why his sister decided not to come back to DWTS as a judge this season.