{blackbabes} Brad Pitt Cracks Hilarious Jokes About Jay Z and Rihanna at RiRi's Diamond Ball

Christmas - Michael Bublé / Elf (2003) / Scrooged

Brad Pitt had a fun time introducing Rihanna's performance last night at the singer's inaugural Diamond Ball charity gala in Beverly Hills.

With a photo of a young RiRi flashing on large screens adjacent to the stage, Pitt said with his tongue firmly planted in his cheek, "I've often asked the very questions you yourself are asking right now—what the f--k went wrong?

"I give you exhibit A," he said. "Look at the young girl before you, all full of hopes and dreams, living a humble existence in Barbados, her whole life ahead of her."

Pitt said Rihanna landed in New York City at just 16 years old, but "soon fell in with a bad crowd led by the dubious and nefarious character known as The Jay Z."

"For those you not in the know, The Jay Z was an evil impresario known for turning out hit records and ripping insane lyrics and fresh beats," he said as the room erupted with laughter. "Needless to say it was all downhill from there."

Pitt didn't stop there.

He listed Rihanna's many accomplishments, including selling 54 millions albums, winning seven Grammys and having "only 90 million Facebook fans and 40 million Twitter followers," but then pleaded with the crowd to intervene, because he fearED she could end up like, well, a photoshopped image that popped up on the screens showing the music star overweight and eating a sandwich while laying on a couch.

"I ask that we stand together by her side and show her our support and our love and say to her the hard words, 'Rihanna put down that sandwich, get off your ass and do something. God damn it, just do something with your life,'" Pitt cracked.

RiRi then stepped onto the stage in a gorgeous dark blue gown and huge Chopard diamond necklace and sang a medley of her hits with a live orchestra.

So how did Rihanna get Mr. Pitt to introduce her? "Brad Pitt loves charity, he loves giving back and it was just as simple as that," she told me on the red carpet. "He was honored to be a part of it, so I'm really happy he's here."

The evening, which benefited Rihanna's The Clara Lionel Foundation, also featured a live auction that included Salma Hayek winning a Damien Hirst artwork for $190,000. Four VIP tickets to an upcoming Kanye West concert went for $74,000.

Gift bags for all the guests included bottles of Rihanna's new Rogue fragrances and MAC Cosmetics' RiRi Woo lipstick.

Jimmy Kimmel hosted the festivities, which was sponsored by Grey Goose Vodka and D'usse Cognac. Celeb attendees included Kim Kardashian, Kris Jenner, Nikki Reed, Kat Graham, Big Sean, Ellen Pompeo, race car driver Lewis Hamilton, Adrienne Bailon and Tyrese Gibson.