But perhaps there was a more sinister motive behind the unusual garb. The theory's been posed he wore the balaclava to take a pot shot at McGregor's nationality (he's Irish), a Reddit user pointing out the similarities between the ski mask and garments worn by members of Irish terrorist group the IRA.
McGregor hails from Dublin and was alive as the IRA attempted to stage a violent separation from the UK across several decades.
Writing for Crave Online, Paul Tamburro said ski masks were commonly used by IRA members to conceal their identity and claimed Mayweather's choice of attire "may have actually been a subtle (albeit brutal) cheap shot at his opponent's nationality".
"Given McGregor's frequent references to his home country throughout the build-up to the fight - at the weigh-in he repeatedly shouted 'Eire!' in Mayweather's face - it seems more likely that this was a dig at the UFC champion's beloved homeland," Tamburro wrote.
Mayweather wasn't the first boxer to take to the stadium dressed in a bizarre costume.
Earlier, Baltimore's Gervonta Davis arrived looking more like a Sesame Street character than a pro-boxer.
Taking to the ring for the final undercard fight ahead of the main event, Davis wore an electric blue fuzzy hood - and matching tassels on his feet.
The 22-year-old, who won his fight against Francisco Fonseca of Costa Rica in the Super featherweight bout, was not only compared with Papa Smurf - but also for his similarities to the Cookie Monster.
"I'm afraid Gervonta Davis killed a Muppet before going to the arena," one fan said on Twitter.
Davis, who won against his opponent, matched his fluffy head dress with tassels on his boxing shoes - which were snipped off his feet.
"Gervonta Davis walking in looking like the Cookie Monster," another added.
