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Russell Brand was as unpredictable as ever at the Hollywood premiere of Rock of Ages, showing off his maternal side during a chat with The Insider's Brooke Anderson.

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Russell first surprised Brooke with a friendly, though uninvited, peck on the cheek. Then, knowing that it was close to dinner time, the rock star comedian offered Brooke a snack.

"You need to be breast fed like the Time cover," said Russell, pulling Brooke's head near his exposed nipple.

Brooke kept a good sense of humor about the joke, saying simply, "You never know with Russell."

VIDEO: Rock of Ages Cast Plays 'Finish The Lyric'

The other unpredictable portion of the night had to be the stars' fashion -- most notably Malin Akerman, who wore a Reem Acra gown with a dangerously high thigh slit.

"I think at the first moment I put it on [my husband] just went, 'How are you going to wear underwear with that?" said Malin, who's been married to Roberto Zincone since 2007. "I said, 'Don't worry, honey, we'll figure it out.'"

Julianne Hough also wowed fans, appearing in a chartreuse-colored Kaufmanfranco gown that she said was inspired by '80s fashion.

The man of the hour, Tom Cruise, was more dialed back with his black carpet outfit, but don't let the clothes fool you -- Tom is a bona fide rock star.

"I spent about five hours [voice training] for about four and a half months, plus the dancing," said Tom, revealing how much he dedicated himself to the role.

VIDEO: Rock of Ages Cast Covers Journey Tune

Diego Boneta, Alec Baldwin, Paul Giamatti, Mary J. Blige and Catherine Zeta-Jones are just a few of the other members who filled out the star-studded cast in this rags-to-riches rock 'n' roll fable.

Real-life rock legend Gene Simmons raised the level of authenticity for the event with his presence and used the opportunity to encourage a few specific artists to be more authentic with their own careers.

"The thing with [rock] music is that it has integrity," said Gene, who has been displeased with the amount of lip-syncing that takes place during live shows nowadays. "No matter what you do, get up there and sing live. Have some integrity," Gene continued, going on to name Rihanna, Madonna and Britney Spears as high-profile offenders.

There was no questioning Catherine Zeta-Jones' integrity when she broke out in song for The Insider cameras. Take a look at the video for more.

Rock of Ages hits venues everywhere June 15.