Marc Malkin

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Prince rocked out in Hollywood. Leonardo DiCaprio chummed around with two very special ladies in NYC. Hilary Duff hit the Windy City. Get ready, because I’m about to give you the lowdown on who was doing what and where and with whom this weekend.

Penélope Cruz chatted up a storm with Sean "Diddy" Combs before Prince’s concert Saturday night at the Hollywood Roosevelt hotel, an eyewitness tells me. The two started their evening off at the Bombay Sapphire party at Mr. Chow in Beverly Hills to celebrate Pharrell Williams’ gig as the official musician of this year’s Los Angeles Film Festival. I’m told Combs made a beeline for Cruz as soon as he walked into the famed eatery.

But Cruz seemed even cozier with Vanessa Williams’ ex-husband and former NBA star Rick Fox during the Purple One’s performance.

Also there were Hilary Swank and her agent boyfriend John Campisi, Erykah Badu, Chris Brown, Topher Grace, Jay Mohr and wife Nikki Cox, Suge Knight and legendary producer Robert Evans. Nikka Costa joined Prince onstage for the night’s last number, a rocking rendition of "Purple Rain."

Three thousand miles away in New York City, Leonardo DiCaprio palled around with Ellen Barkin and Mary-Kate Olsen at Amy Sacco’s über-exclusive Bungalow 8 lounge.

Hilary Duff hit Chicago to promote her new album. She and a gaggle of girlfriends had dinner at Billy Dec’s Rockit Bar & Grill before heading upstairs to the eatery’s lounge to shoot a couple of rounds of pool. Duff then took her leave through a back door.

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Kimora Lee Simmons and Djimon Hounsou are going strong. I spotted them on Saturday strolling down L.A.’s über-trendy shopping street Robertson Boulevard.

And speaking of couples, Broadway star Kristin Chenoweth’s on-again, off-again boyfriend, Aaron Sorkin, hung out in her green room as she performed at the opening night of the Hollywood Bowl on Friday. Before hitting the stage to honor one of the night’s Hollywood Bowl Hall of Fame inductees, Plácido Domingo, Chenoweth called her mom, a source tells me.

The founding director of the Bowl’s orchestra, John Mauceri, then held up the phone so Chenoweth’s mom could hear her daughter perform, including a duet with Domingo of Jerome Kern’s “Make Believe.”

I’m told Chenoweth was in tears when she dashed backstage to say goodnight to her mom.

On a much lighter note, Jack Black was the victim of some rather odd mistaken identity before the Bowl show began. The funnyman was walking in through the stage door when a man asked him if he was—ready for this?—Plácido Domingo.

When Black said he wasn’t, the man then asked him who he was. According to an eyewitness, Black simply replied, “Some other guy."