Energy seeped from the fighters as they were forced to make weight for the boxing match. McGregor entered the ring sporting flip-up sunglasses and an Ireland flag draped over his shoulders. Notorious B.I.G.'s Hypnotize played during his introduction.
"Money" Mayweather walked into the arena wearing a white TMT hat and matching shirt. Phil Collins' In the Air Tonight blared from the speakers.
Both men ripped off their clothes and went down to their briefs before stepping on the scale. "The Notorious" weighed in at 153 pounds, while Mayweather weighed 149.5 pounds. McGregor said he plans to fight at 170 pounds.
Mayweather (49-0, 26 knockouts) has never weighed in at more than 151 pounds.
After several screams and flexes, the fighters stood face-to-face. McGregor started shouting insults at Mayweather and screaming wildly. Mayweather remained silent during the exchange.
Showtime's Jim Gray then interviewed the two fighters.
"He looks like dog [expletive]," McGregor said. "You know that. He looks blown out. Full of water. He's not going to keep my pace. Trust me on that. That's the worst shape I've ever seen him."
"That's the worst shape I've ever seen him in. He looks blown out. Out of shape. I'm going to breeze through him. Trust me on that."
McGregor also answered to rumors that he wouldn't be able to make weight for the 154-pound limit bout.
"153. I'm a professional. I make weight. It's sacrifice. It's dedication. It's focus. But I make it. And that's it. Look at me. I'm in peak physical condition. I put in the work as everyone can tell. I'm ready," McGregor told Gray.
The Irishman said that he plans to stomp his foot in the middle of the ring and not go anywhere during the fight.
Mayweather, 40, took a different approach.
"I've been here before," he told Gray. "I know what it takes when it's a fight of this magnitude. So I did a lot of this [talking]. He did a lot of this [talking]. But tomorrow it comes down to the fighters."
"Weight doesn't win fights. Fighting wins fights."
Mayweather said the fight won't "go the distance" against his 29-year-old foe.
"I just want to thank the fans. I'm not really worried about the scale or the last time. This will be Conor McGregor's last fight also."
Saturday's fight is expected to start at about 9 p.m. on Showtime pay-per-view. It will cost about $100 to watch in high-definition.