He had a bottle of whiskey in one hand and a glass in the other.
"What's up everybody? Hello," he said. "I'll put my whiskey down. Notorious Irish whiskey. Coming soon ... Do I answer questions or do I just rattle on? Rattle on? No problem."
The press pack immediately sensed they were in for a treat and McGregor began a wonderfully honest breakdown of his performance.
"It was a good fight. I thought I smoked him in the early rounds," he said, before directly addressing Mayweather, who remained onstage. "But I tell you what, you are one composed individual. You didn't get rattled. You tucked in when you needed to tuck in. I thought you changed your game plan three times. Came out looking to box - I thought you were being outboxed early on.
"You (then) looked to play against the ropes, you were getting picked off there. And then you came in hands up to your forehead, head dipped in on your chest and you fought that kind of fight. I didn't anticipate that.
"Three game plan changes in the fight. That's what a true champion does. Much respect. You came with it. I got to give respect to that."
McGregor admitted he had been frustrated by Mayweather's movement and the restrictions of a boxing match. He regularly found himself behind his opponent but was unable to attack from that position - like taking his back for example - like he would in the Octagon.
"Midway through the fight when I was at his back and the referee was just resetting us and resetting us and somewhere in the middle of all that I was like 'I'm using valuable energy here to get to this man's back and we're being reset to go again'," McGregor said. "So it kind of flustered me a little bit and he was able to capitalise on it."
McGregor kept sipping from his cup and became more raucous the longer he spoke. He cackled when Mayweather answered a question about the difference between MMA and boxing by saying "the cheque" before interrupting a reporter to rave about the alcohol he was drinking.
"Ooh that whiskey tastes so good! Oh s***. Notorious Irish Whiskey. Coming soon," he said.
"I'm going to take over the Irish whiskey market. And this is delicious. So keep an eye out for it."
Asked what his next move would be, McGregor said he was ready to fight again soon but would first head to Ibiza.
"I'm young, I'm fresh and I'm ready. I was just tired in there. He caught me with some shots but I wasn't dazed or rattled, you know what I mean? I was just bollocksed, is the term we all it in Ireland," he said.
"We'll see what happens. A childhood friend of mine is getting married. We're going to charter a 100-foot yacht. Maybe for a day. F*** paying for a whole week. I'll just (get) it for a day, have a party on it, take a load of pictures and then get the f*** off it. That's my plan - and then I'll see what's next."
It might have been the booze, but McGregor was genuinely OK with how the night went.
"I enjoyed myself and that's it," McGregor said. "Long may it continue."
Cheers to that.
