Katy Perry [1] celebrated her waning days as a single woman with Rihanna [2]'s help at her bachelorette party in Las Vegas on Saturday (Sept. 18). With a group of 25 girlfriends, Perry toasted her impending wedding to actor/comedian Russell Brand with an all-day affair that caused the singer to post on her Twitter [3], "Signing up for a liver transplant now."

According to People [4], the party began poolside at the Hard Rock Hotel Beach Club on Saturday afternoon, with Perry sporting a white bikini with a veil hanging from the back of her bikini bottom. Perry then brought Rihanna and the rest of her crew to the MGM Grand Hotel/Casino to check out a performance of Cirque Du Soleil's "KA."

The group later grabbed dinner at Ago and relaxed at a VIP table at XS nightclub. The night ended with a visit to Sapphire strip club.

The bachelorette party followed Brand's arrest on Friday [5] (Sept. 17) after getting into a fight with a paparazzo at Los Angeles airport. After the incident, Perry posted on her Twitter [6], "If you cross the line & try an put a lens up my dress, my fiancé will do his job & protect me. #standbyyourman #don'tfuckwiththeBrands."