Both McGregor and KSI were ringside at the O2 Arena for Joshua’s knockout victory over Robert Helenius.
As soon as landing the finishing right hand, AJ leapt out of the ring for a victory lap around the ring.
He bumped into McGregor and swigged some of the UFC superstar’s Forged Irish Stout.
McGregor then pointed to KSI and called him a b**** but Joshua responded: “That’s my guy.”
One fan said: “AJ a real one.”
Another added: “Respect @anthonyjoshua for not going against a friend.”
McGregor went one further by calling out the YouTuber to a bare-knuckle fight in the ring.
He said: “Big congrats to AJ, big congrats to Eddie, big congrats Forged Irish Stout.
“And I know your man KSI is in the crowd and he couldn’t box eggs if he worked in an egg boxing factory.
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“So if he wants to get in here I’ll give him a final yoke, bare-knuckle if you want.”
Responding, KSI tweeted: “Lmao just seen this.
“Jake Paul must be crying that I’ve got Conor on my d*** already and I didn’t even have to fight an mma fighter.”