Arriving 14 minutes late to the festivities inside the Theater at Madison Square Garden, McGregor stole the show just two days ahead of the UFC's inaugural card at "The World's Most Famous Arena."
"I run New York City," he boldly proclaimed. "I'm a f---ing pimp."
McGregor (20-3), who is looking to become the first UFC fighter to hold titles in two weight divisions simultaneously when he faces lightweight champion Eddie Alvarez (28-4) on Saturday, was his usual theatrical self in a wild, expletive-filled news conference.
The Irish star briefly stole Alvarez's 155-pound belt and needed to be restrained by security after he picked up Alvarez's chair, raised it over his head and threatened to use it as a weapon during a chaotic sequence.
McGregor was fined $150,000 for throwing water bottles at Nate Diazin August during the UFC 202 news conference, one he also was tardy to. He had fun with the moment Thursday, saying, "I wonder how much a chair would've cost me?"
Alvarez, meanwhile, was visibly upset Thursday, and he walked off the dais five minutes in after delivering an angry statement.
"I don't even have an opponent," he said. "I'll see you guys tomorrow. When he comes, you give me a call."
After his arrival, McGregor said, "Sorry I'm late, I just don't give a f---." Asked moments later about where he was, he said, "I operate on my time, I operate on my own time. And I'm running early on my time."
UFC president Dana White wasn't worried about the fighter's actions and said McGregor wouldn't be fined.
"No, it doesn't piss me off," White said. "This is fighting, man -- a wacky, crazy, crazy business. I'm in such a good mood for this event. It is what it is."
McGregor, dressed in a white mink coat, predicted a first-round knockout of Alvarez, saying, "I predict I rearrange his face. He's too easily hit." But the 145-pound champion wouldn't budge when asked to clarify rumors he will make a special announcement after Saturday's fight regarding his intention to take time off in 2017.
"Don't worry about it. Just buy that pay-per-view twice," McGregor said. "I'm only warming up, I'm only warming up. I'll take all them damn belts you have."
McGregor enters Saturday's bout on a short turnaround having gone five hard rounds with Diaz less than three months ago. He downplayed the lingering effects of a leg injury that left him limping after the Diaz fight.
"I'm fresh, ready to go," McGregor said. "I look forward to [Saturday]. I'm going to shut this man up."
Saturday's card marks the UFC's debut in New York City after a bill was passed in March that lifted a ban on professional mixed martial arts in the state that dated back to 1997.
McGregor says the 'whole ship sinks' without him
After showing up late to the UFC 205 news conference, Conor McGregor says he's here to take over New York City and that without him, the "whole ship sinks."