In fact, Justin and Lil Wayne didn't just attend the event, they helped amp up Mayweather.
The two artists walked the fighter in to the ring to face Alvarez, with a shirtless Lil Wayne performing a live remix of his hit song "A Mili" while the Biebs rocked black sunglasses and a plain black T-shirt.
The threesome's entrance had everyone from Seth MacFarlane to David Spade talking. Seth lightheartedly tweeted: "Nice to have Whoopi Goldberg here with--oh sorry, Lil Wayne." Whereas Eliza Dushku was thinking what we all were thinking: "Wait, I'm still stuck on #Bieber is #Mayweather's #HypeManJr..? #Alvarez #FightNight"
Spade didn't hold back, Instagramming a pic of their entrance with the caption: "WTF?? One of these things doesnt belong. He needs to be cropped! #teamcoughsyrup"
Mayweather took the win, after an intense 12 rounds and an even more intense majority-decision victory.