Inside Katy Perry's Vegas Bachelorette Bash With Rihanna

USMagazine, Sunday, September 19, 2010, 7:31am (PDT)

Bride-to-be Katy Perry woke up in Vegas on Sunday -- after a wild night out!

Set to wed British comic Russell Brand this fall, Perry, 25, hit Sin City on Saturday night with best friend Rihanna and 25 other guys and gals for an epic bachelorette party.

Before heading out for the night, Perry jokingly Tweeted about her upcoming night of Las Vegas debauchery: "Signing up for a liver transplant now." She then quoted 9-year-old Willow Smith's club banger: "I whip my hair back 'n forth."

The festivities began when Perry, Rihanna and the rest of the revelers arrived at the MGM Grand in a stretch Hummer convertible. As the limo pulled up, Perry (wearing a crown) and Rihanna bopped to blasting music.

The gal pals were arm in arm as they entered the back-door entrance of the resort to check out an early performance of KA by Cirque du Soleil.

After the show, the famous singers visited with the Cirque du Soleil cast backstage, playing with their out-of-this-world costumes and complimenting the performers' amazing, freaky show.

The party continued on into the night as the crew boarded the stretch Hummer, headed for a top-secret location.

Perry and "Get Him to the Greek" star Brand, 35, got engaged over New Year's while on vacation in Jaipur, India. The "California Gurls" singer has "never connected with anybody like this," a pal told Us.

Perry's bachelorette weekend admittedly got off to a rough start: She and Brand missed their Friday flight out of LAX after he reportedly got into a scuffle with a photographer. Brand was placed under citizen's arrest and charged with a misdemeanor of simple battery. He was released on $20,000 bail.

Perry defended Brand on Twitter after the brouhaha: "If you cross the line & try an put a lens up my dress, my fiancé will do his job & protect me."

More on Wonderwall:

Rihanna's tutu and more fashion boo-boos

Does Katy want to make Russell a farm boy?

Russell Brand charged with battery after LAX scuffle

More from UsWeekly:

PHOTOS: Katy's smushed boobs

PHOTOS: Stars show off HUGE engagement rings

PHOTOS: OMG! Katy's super-wacky style