One day after announcing his retirement from singing, pop music’s favorite confection, Justin Bieber, walked the purple carpet on Dec. 18 at L.A. Live for the world premiere of “Justin Bieber’s Believe,” director Jon M. Chu’s documentary follow-up to 2011’s massively successful “Justin Bieber: Never Say Never.”

Bieber, flanked by bodyguards and decked out in a dapper red suit, his hair a rolling bouffant of blond, braved throngs of screaming, weeping “Beliebers,” clutching purple roses and waving homemade cardboard signs that begged for movie tickets while chanting “We want Justin!” in perfectly timed unison.

“I’m the biggest Bieber fan there is,” gushed comedian Chris D’Elia, who recently roasted Bieber at a Laugh Factory show. Citing the singer’s “drop crotch pants” as one of his favorite fashion items du jour, D’Elia is a true Belieber. “I love them. And I love Justin. I predict that in five years he’ll run for governor of California. I would 100 percent vote for him.”

PHOTOS: ‘Justin Bieber’s Believe’ Premiere at L.A. Live

Usher, Holly Robinson Peete and Chris Meloni were among the celebs on hand to celebrate the latest unfolding of Bieber Nation, as well as a slew of budding young stars, including Disney Channel’s Debby Ryan, Kylie Jenner, Kiernan Shipka and Jaden Smith.

Brad Garrett scored major dad points for bringing his teenage daughter, Hope, to the event sponsored by, natch, Clearasil and Teen Vogue.

“It’s insane,” Garrett marveled of the surrounding mayhem, the squealing tweens, the clicking cameras, the crush of hungry press. “The energy, the girls. To be nineteen and be a giant star in front of millions of people — it’s very exciting. Tonight, it’s all about the Biebs.”

Of the stream of negative press that Bieber has been fielding of late — the Anne Frank gaffe, the accusations of pot use — Meloni, who came with his own daughter in tow, offered this sage career sound bite: “As an artist you gotta morph in ways that are true to you.”

Perhaps no one knows the real Bieber better than “Top of the World” singer, songwriter and producer Mike Posner, who turned up to support his friend and fellow musician.

“Justin is one of the most loyal people I know,” declared Posner, who collaborated with Bieber on his 2012 hit single “Boyfriend.” “Having worked with Justin in the studio, I can say that he’s extremely talented. He’s the real deal—as a singer, as a songwriter, he plays drums, piano, guitar. When it comes to his music, he’s quite fearless.”

For “Believe” helmer Chu, who’s watched Bieber grow from scrappy adolescent to formidable media juggernaut, what impresses him most about the Canadian-born superstar is the way he openly and graciously embraces his fans.

“I love that he is genuine,” said Chu. “He’s got all of these people around him, all the time, but as soon as he sees that girl in the audience, or in the crowd, he locks in on her. He gives that attention to you, he gives you that warmth, and I think that’s why he’s a star.”

Also on hand were Open Road’s Tom Ortenberg, Jason Cassidy and Scooter Braun.