Conor McGregor knocked out Dennis Siver in the second round in Boston, Massachusetts.,
The Irishman then climbed over the top of the Octagon wall and went face-to-face with Jose Aldo, the featherweight world champion, who was seated ringside.
McGregor is likely to be Aldo's next challenger, although plans to fight in Dublin have been shelved for a Las Vegas showdown in May.
The 26-year-old required almost seven minutes to put away Siver but had dominated the fight until the referee stepped in.
A multitude of kicks kept Siver at bay for the opening round and the bell seemed to save him when he needed it most as McGregor upped the ante.
But at one minute 54 seconds of the second round, a straight left from McGregor put Siver down and the rest was a formality.
The partisan Boston crowd, heavily Irish in heritage and backing McGregor, went into a frenzy when the night ended with security guards separating the winner and Aldo at ringside.