The Gladiator star hit headlines in 2005 after taking aim at Hollywood heavyweights Clooney, Robert De Niro and Harrison Ford for cashing in on their fame by fronting commercials for a range of products.
He told GQ magazine, "I don't do ads for suits in Spain like George Clooney or cigarettes in Japan like Harrison. It's kind of sacrilegious, a contradiction of the contract with your audience. De Niro advertising American Express - gee whiz."
Clooney took the fiery actor's comments in his stride and replied to the criticism in his own comical way, poking fun at Crowe's musical pursuits with his band 30 Odd Foot of Grunts in a statement which read: "I'm glad he set us straight. Because Harrison, Bob and I were putting a band together called Grunting for 30 Feet, and that would also fall under the heading of 'bad use of celebrity'. Thanks for the heads up."
The tongue-in-cheek response only irked Crowe further, prompting him to lash out again, but this time, Clooney had had enough and decided to clear up the issue by confronting his fellow screen star in private.
Discussing the statement, Clooney tells Esquire magazine, "That's when he really went off on me. 'Who the f**k does this guy think he is? He's a Frank Sinatra wannabe.' He really went after me. And so I sent him a note going, 'Dude... what the f**k is wrong with you?'
"So he sends me a disc of his music and a thing of his poetry. I think he said, 'I was all misquoted,' and I was like, 'Yeah, yeah. Whatever.'"
He continues, "The truth is that (Crowe) did send me a book of poems to apologise for insulting the s**t out of me, which he did. He picked a fight with me. He started it for no reason at all."