With her new pal Diddy by her side, Britney Spears declined to stay in and rest up for the big show, instead bouncing from club to club along the Strip, and even hanging with Paris Hilton.
After taking in a Saturday-night performance of Cirque du Soleil's Mystere with four friends, Spears headed to the Hard Rock Hotel's Body English for the 50 Cent album release party.
Diddy and Spears slipped into a booth with Hilton and 50 Cent. The crowd went wild when the deejay gave a shout-out to Spears, who bobbed her head to Lil Jon's "Snap Yo Fingers" in unison with Hilton.
Then around 1:30 Sunday morning, Spears and Diddy, along with an entourage of about 20, headed to Tao Nightclub for the Samsung party hosted by Pharrell. There, Spears – dressed in a champagne-colored dress, oversized sunglasses and a grey fedora hat – sat with BFF Alli Sims drinking vodka and sugar-free energy drinks.
"She was having a good time, but was real mellow," an onlooker said. "She was having her assistant order drinks for her."
After 45 minutes in Tao, Spears, Diddy and the crew jetted off just as the deejay put on the pop star's new song "Gimme More".
Next stop: Jet Nightclub, to help celebrate the 21st birthday of R&B star Cassie. Arriving sans glasses and hat, Spears and Diddy made their way to Cassie's VIP table, and the popster gave her a hug.
"We wanted to be here for our girl Cassie," Diddy said into a microphone. "Happy birthday, girl."
All VMA Photos, Quizzes & More
with reporting by JESSICA HERNDON
Click here to get the scoop on Britney's Friday night adventures in Vegas.