Mayweather-Pacquiao Fight's Biggest Bashes: Leonardo DiCaprio, Ben Affleck, Diddy Party in Las Vegas

Diddy and Brett Ratner party on Friday at Lavo Nightclub in Las Vegas.

Drew Barrymore was among the fans who lost money by betting on Manny Pacquiao.

Fight weekend in Las Vegas was an epic show of hype and celebrity, befitting what has been deemed among the most significant sporting events of this or any other time.

The crush of crowds, the multitude of private jets on the ground (reportedly 720 of Net Jet's 750 flights were in Vegas) and an influx of A-listers from film and television created a scene the defied description.

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The energy was bubbling over starting on Friday, with the pre-fight parties that took over every major venue on the Strip. Mark Ronson reportedly set up a DJ booth in his room at The Cosmopolitan before headlining Marquee on April 30. Sean "Diddy" Combs hosted an invite-only affair at Lavo Nightclub in The Palazzo for Showtime and his Ciroc and DeLeon brands. The tables were fully stocked with Aquahydrate, the water brand backed by Combs and Mark Wahlberg, who made a $250,000 bet on the fight earlier in the week. Cassie, Bradley Cooper, Brett Ratner, Showtime executive Stephen Espinoza, Leonardo DiCaprio and Pete Radovich partied into the wee hours.

On Saturday night, the epicenter of the universe was the MGM Grand Garden arena, as celebrities descended on Mayweather Promotions' and Top Rank's official pre-fight party. The event kicked off with Mayweather personally greeting Denzel Washington at his car and walking him into the venue, even though it was just hours before the fight. Washington, clad in a head-to-toe blue Adidas tracksuit, casually chatted with friends inside the party sponsored by Tecate and Hennessy. The actual WBC belt, encrusted with 3,017 emeralds and made by 20 artisans in Mexico, made the rounds at the party, giving guests a chance for the ultimate photo op.

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Jamie Foxx arrived around 6 p.m., wearing headphones and avoiding the crowd. Jimmy Kimmel, Jon Voight, Sting, Simon Hammerstein, Ben Affleck, Jake Gyllenhaal and Drew Barrymore were seen scurrying around backstage at the arena in a scene that was befitting a major awards show, rather than a sport event. "I am here supporting my husband," Barrymore said. "I'm rooting for Pacquiao, Philippines. I made a $100 bet." ESPN's Hannah Storm, however, was not playing favorites. "All the years and years of hype have added up to this, and I have no idea who is going to win," she said.