Fight night: Celebs attend Mayweather-Canelo

Mayweather Jr. and Bieber celebrate Mayweather's victory over WBC/WBA 154-pound champion Alvarez at the MGM Grand Garden Arena in Las Vegas, Nevada

Floyd Mayweather Jr. (L) and singer Justin Bieber celebrate Mayweather's victory over WBC/WBA 154-pound champion Canelo Alvarez (not pictured) at the MGM Grand Garden Arena in Las Vegas, Nevada, September 14, 2013. Alvarez was previously undefeated in 42 fights. REUTERS/Steve Marcus (UNITED STATES - Tags: SPORT BOXING ENTERTAINMENT)

VIP Pre-Fight Party For Showtime PPV's Presentation Of The One: Floyd Mayweather Jr. Vs. Canelo Alvarez

LAS VEGAS, NV - SEPTEMBER 14: Recording artist Sean "Diddy" Combs attends the Floyd Mayweather Jr. vs. Canelo Alvarez boxing match at the MGM Grand Garden Arena on September 14, 2013 in Las Vegas, Nevada. (Photo by Bryan Steffy/Getty Images for Showtime)

Wayne Gretzky is seen during an IBF junior middleweight title fight between Carlos Molina and Ishe Smith, Saturday, Sept. 14, 2013, in Las Vegas

Wayne Gretzky is seen during an IBF junior middleweight title fight between Carlos Molina and Ishe Smith, Saturday, Sept. 14, 2013, in Las Vegas. (AP Photo/Mark J. Terrill)