The Jonas Brothers haven't changed much since they made their 3-D debut in "Hannah Montana and Miley Cyrus: Best of Both Worlds Concert Tour" — you know, aside from having multiplied their legions of dedicated fans, releasing a hit album, creating their own TV show and getting the opportunity to star in their own 3-D movie.

"They're absolutely still as grounded," said one of the movie's producers, Art Repola, who also got to know the brothers when he worked on "Best of Both Worlds." "They do the whole thing. I think they continue to get better. And they're absolutely as grounded as before."

(Check out two exclusive photos from the Jonas Brothers' movie here.)

The film sets out to give fans complete access to the guys, from the time they get onstage to the intimate moments they spend off of it, including shooting a video for the brand-new song "Love Is on Its Way." Repola boasted that even if you've been to one of their shows, this movie is still a better experience.

"I think if you went to the concert and you sat in the front row, your seats are not as good as it's going to be in the film," he said. "I think to really see what's going on beyond watching a music video of concert film, that'll be the best experience. It's surprising when you see the film and you see the size of the crowds."

Repola, who describes the brothers as "crazy famous" and "the real deal," said that it was eye-opening to spend every moment with them and experience their hectic lives first-hand.

"I just think [the fans are] going to be surprised at the cumulative experience of what happens from the time they wake up to the end of the day," he said. "It's not a band where they have a show that night and they're lying around the hotel. It's constant appearances and interviews and events. I think it'll be surprising."

Repola recalled one moment in particular when he witnessed the pinnacle of JoBro chaos. "The record dropped in Times Square, and there were 15 or 20,000 fans there at midnight on a weekday," he explained. "The amount of the excitement was overwhelming. And it never stops."

Taylor Swift and Demi Lovato make cameos in the movie, and Repola likens their appearances to the ones made by superstars in the Martin Scorsese/Rolling Stones documentary "Shine a Light."

Despite all their success, Repola walked away from the experience thinking the boys are "just incredibly polite, incredibly smart, no nonsense. Fun, but no nonsense," he said. "I think that's refreshing today. They're teenage guys and rock-and-roll stars at the same time."

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