Back in 2014, Johnson had compared Clooney to Hitler following comments over the Parthenon marbles, which are a collection of long-contested Classical Greek marble sculptures on display at the British Museum.
Then-Mayor of London, Johnson told the Telegraph in response to the actor's stance: "Someone urgently needs to restore George Clooney's marbles
"This Clooney is advocating nothing less than the Hitlerian agenda for London's cultural treasures."
But it seems Clooney wasn't too peeved by the bizarre comparison - in fact, it ended up working out pretty well for him.
Speaking to the Observer, 59-year-old Clooney recalled how Johnson 'literally compared' him to Hitler.
He said: "It was kind of great for me!
"Amal and I were secretly dating at the time. No one knew. There was all this uproar about what I'd said. And I was meeting Amal for dinner that night."
Alamuddin, as Amal was previously known before she married Clooney, had been hired as a lawyer to argue the Greek case for the return of the marbles, meaning she'd been able to brief her dinner companion in depth - something that he says forged a strong bond between them, shaping their shared passion for campaign work.
Crediting Johnson, Clooney joked: "I'll send him a note. A thank you note. And a comb."
Clooney also explained that he enjoys working on high-profile battles alongside his wife, through the foundation they created four years ago to help bring justice to human rights abusers.
He continued: "Working less on movies, working more on life. I gotta tell you, it's been pretty fun chasing some war criminals around."
Clooney added that it also helps him be a better father to their three-year-old wins, Alexander and Ella, saying: "I just feel like, with kids this age, having young children in a period of time when there's all this craziness, I wanna make sure I can say, 'these are the things we did to stand against this moment in history'. Not just to make them proud. But to make their world better."
Chosen for YouChosen for You
Most Read StoriesMost Read