Conor McGregor has been key to a lot of big UFC moments in his time with the promotion. But perhaps none was bigger than when he became the first fighter in UFC history to hold two titles at the same time. McGregor was featherweight champion following a 12-second knockout of longtime champion Jose Aldo in December 2015. In November 2016, he returned at UFC 205 at Madison Square Garden, arguably the most famous fight venue in the world, and took the lightweight crown, too