Kim Kardashian can’t pass up a great party, even if it’s not hers!

The newly engaged vixen held her bachelorette party in Las Vegas at Tao over the weekend, while fiancé Kris Humphries had his bachelor party next door at LAVO — and RadarOnline.com has learned Kim couldn’t resist popping next door to crash his party.

Bachelor and bachelorette parties are typically held separately, but Kris had no problem with Kim stopping by and even laid a wet one on her in front of the whole nightclub.

Hundreds of highly intimate photographs of Christina Aguilera have surfaced,including candid images of the star partying at Nicole Richie's bachelorette party and in bed with her boyfriend Matt Rutler.

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The provocative images of the Dirrty pop star -- who split from her husband of five years, music producer Jordan Bratman last year -- were on a digital storage card that was found in a French hotel, RadarOnline.com has exclusively learned.

Talk about taking the plunge: future bride Katy Perry donned a sexy white bikini at her bachelorette pool party in Las Vegas this weekend, and RadarOnline.com has the pics.

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The Teenage Dream singer threw her wild pool party at the Hard Rock Hotel Beach Club on Saturday, and  fellow singing star Rihanna, wearing a bright red wig and a sparky gold one-piece, was among the pals taking a dip with Katy and enjoying a few cocktails.

Rihanna is sending Katy Perry off to marriage with a bang. The R&B singer threw the pop star a fabulous bachelorette party in Las Vegas Saturday night and RadarOnline.com has the pictures.

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Now we know why Katy Perry and fiancé Russell Brand were headed to Vegas Friday when he got arrested for tangling with a photographer at LAX.  Rihanna was throwing the bride-to-be a Sin City bash!

Fortunately Katy still got there in time, and the girls plus 25 of their closest friends started Saturday night by seeing a performance of KÀ by Cirque du Soleil at MGM Grand.

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After the performance, they headed backstage for a meet-and-greet with the amazing cast.

Then it was on to dinner and a long night -- and early morning -- of clubbing.

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And nobody got arrested!

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No, Rachel Bilson has not reunited with one-time fiance Hayden Christensen. Instead, the brunette beauty is getting her wedding kicks by celebrating someone else’s nuptials, RadarOnline.com has learned.

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Bilson, whose engagement was called off earlier this month, celebrated her best friend’s bachelorette party in Las Vegas over the weekend. “Rachel was in a really good mood,” a source told RadarOnline.com. “She was super sweet with her friend the bride-to-be and stuck by her side throughout the day and night.”

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Bilson and her group of long-time friends (some even went back to high school!) took over a cabana at TAO Beach on Saturday, drinking Hpnotiq cocktails and checking out the bachelorette goodie bag. “Rachel didn’t pay attention to any guys,” the source added.

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However, the actress did kick up her heels. After hitting LAVO for dinner, the ladies headed to VIP table at TAO Nightclub. “She was definitely dancing and drinking, laughing a lot,” the source said. The party danced until the wee hours of the morning, even sporting blue Hpnotiq boas and tiaras.

“Rachel didn't show any signs of being broken hearted!”