Garfield may hate Mondays, but Bill Murray loathes Garfield.

The “Caddyshack” star, who voiced the finicky feline in 2004’s “Garfield: The Movie,” revealed he took the part because he mistakenly thought it was penned by famed film scribe Joel Coen — and not Joel Cohen, a relative unknown.

Murray told fans Friday in a Reddit chat that he didn’t bother to read the hit comedy’s full script because he thought it was written by Coen of “Fargo” and “The Big Lebowski” fame, not Cohen, whose credits include Howard Stern’s failed TV talk show and the film “Cheaper by the Dozen.”

It was only during the recording of his dialogue that Murray watched — in horror — parts of the comedy that were already filmed.

“There was just this long, two-minute silence,” he recalled. “I probably cursed a little, and I said, ‘I can fix this, but I can’t fix this today. Or this week. Who wrote this stuff?’ ”

Murray, an Oscar nominee for “Lost in Translation,” went off on a 15-paragraph screed about the comic-strip-inspired film after a fan asked if there’d be a third installment.

“I don’t think so,” he wrote.

“They sort of shot themselves in the foot, the kidneys, the liver and the pancreas on the second one,” he added, referring to 2006’s “Garfield: A Tale of Two Kitties,” which went straight to DVD.