INSIDE MAYWEATHER-PACQUIAO: Bieber celebrates Mayweather's win, Kimmel gets Pacquiao selfie

LAS VEGAS — Some of the sights and sounds seen by AP journalists covering the Floyd Mayweather-Manny Pacquiao megafight in Las Vegas:

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NO KO? FANS SPLIT ON MAYWEATHER'S STYLE

On one hand, Floyd Mayweather is undefeated at 48-0. On the other hand, he didn't knock out Manny Pacquiao or do much more than repeatedly stuff Pacquiao's attacks.

It's become a classic response to Mayweather's latest fights, echoed again Saturday night on social networks: Too defensive, too boring. Not fun to watch.

"Sorry boxing fans," Oscar De La Hoya said on Twitter following the fight (though take that with a grain of salt — he followed that tweet up with another promoting an upcoming fight, promising "real action").

Fans were certainly expecting Pacquiao to push the pace. But it's a sign of Mayweather's defense — he stops opponents from executing their game plans.

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BIEBER CELEBRATES BACKSTAGE

Justin Bieber again walked into the fight with Mayweather, and after the bout could be seen celebrating in the halls of the MGM Grand Garden Arena (http://bit.ly/1zojdjC ).

Mayweather has said he considers the superstar singer a good kid, saying they have positive interactions when they spend time together.

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Pacquiao's trainer Freddie Roach picked the perfect time to snap a selfie (at least for marketers) — right as the fighter was walking out to fight Mayweather.

"14 years in the gym for 1 night in the ring. #MayPac," one of Pacquiao's staffers tweeted from the fighter's account, along with the selfie (http://bit.ly/1KDRFbg ).

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JIMMY KIMMEL CHANNELS BIEBER

Pacquiao had his own response to Mayweather walking out with Bieber: Jimmy Kimmel, dressed in an outfit similar to what Bieber wore inside the ring during a previous Mayweather fight.

The late-night host pressed to sing the song in Tagalog after performing for Pacquiao on his show "Jimmy Kimmel Live" (https://youtu.be/IKv_0PdBIXY ).

The song was Pacquiao's entrance jam, but Kimmel didn't sing (at least not audibly to the crowd or pay-per-view audience).

At least he got to be in the entourage.

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MEXICO'S ANTHEM

It's a nod to the many fight fans in Mexico, where people are able to watch the fight for free because of a deal made with network TV.

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TEETH OK?

As Manny Pacquiao's dentist, Ed de la Vega kept an especially close eye on any punches Floyd Mayweather Jr. landed to the mouth of the Filipino boxer during their highly anticipated bout.

De la Vega molded Pacquiao's mouth guard about six weeks ago to give the fighter time to acclimate to it. He has worked for Pacquiao for nearly a decade, giving him an up-close view of the boxer -- in the ring and dentist chair.

He said mouth guards for pro athletes - whether the sport is football, basketball, hockey or even badminton - is highly specialized work that can play a major role in preventing catastrophic injuries.

He believes Pacquiao's mouth guard, adorned in the colors of the Filipino flag, is well-made.