Corden also mentioned another A-lister who briefly flirted with the idea of making the film.
The revelation came to light in a Deadline column penned by the outlet's awards columnist and chief film critic, Pete Hammond, who said the outgoing Late, Late Show host dropped "the fascinating little nugget" as they both waited to start a Q&A for the comedian's Amazon series, Mammals.
The story goes, Corden asked Hammond if he'd recently seen anything he liked. Hammond replied with The Whale. Corden said he had not seen the film, but he had a connection to the film.
"I was going to play that part, and Tom Ford was going to direct," Corden told Hammond, while adding that the project fell apart because Ford wanted more complete control. In that same column, Corden felt he may have been too young to do the role any justice. Then, another nugget -- George Clooney briefly got involved. The sticking point? Clooney's said to have wanted to be involved in the project if an actual 600-pound actor played the role that ultimately went to Fraser.
Hammond said The Whale director Darren Aronofsky confirmed Corden's entire story. In any event, Fraser packed on the pounds, made the dramatic physical transformation and portrayed a 600-pound reclusive writing teacher named Charlie, whose health is in life-threatening decline.
Fraser's deft portrayal has earned him Oscar buzz and a Golden Globe nomination for Best Actor (Motion Picture - Drama). He'll face off against Austin Butler (Elvis), Hugh Jackman (The Son), Bill Nighy (Living), and Jeremy Pope (The Inspection).
Back in December, Fraser told ET how his Hollywood comeback in The Whale was inspired by fatherhood. He said he connected with the story of fatherhood, and how that made the making of the film that much more meaningful. Fraser shares three sons -- Griffin, 20, Holden, 18, and Leland, 16 -- with his ex-wife, Afton Smith.
"I have kids now, and that really warrants how I make decisions, what I’m going to do -- and, whatever it is that I’m doing, how I feel about what I’m doing," he shared. "Somehow stakes get raised to such a point that something that may seem garden variety or normal takes on much more gravity."
"I spent the first, I don't know, 25 years of my career or so making films that I generated all the hope and aspiration and joy from what I believed to be coming from a character or a screenplay, and then some alchemy happens when you have kids and suddenly everything clicks," the actor added. "It somehow raises the stakes and somehow, for me at least, increases the authenticity of what we do."