Things between the two men were not grrrrrrr-eat.

Jerry Seinfeld found Hugh Grant to be a “pain in the ass” during the filming of the upcoming movie “Unfrosted: The Pop-Tart Story.”

“We had lots of fights. He’s a pain in the ass to work with. He’s horrible,” Seinfeld, 69, said during an appearance on “The Tonight Show Starring Jimmy Fallon” on Wednesday.

“He tells you before you work with him, ‘You’re gonna hate this.’ And he’s so right,” the actor continued.

Grant plays Thurl Ravenscroft, who voiced the Kellogg’s Frosted Flakes icon Tony the Tiger. The Seinfeld-directed Netflix film will debut in May.

Grant, 63, is part of the ensemble cast alongside Melissa McCarthy, Daniel Levy, Fred Armisen, James Marsden and Jon Hamm.

Despite their quarrels, Seinfeld and Grant set their differences aside after going out to dinner.

“We shot for 10 weeks, and that night that he and I had dinner — and we got drunk having dinner — that was the greatest night,” Seinfeld recalled to a shocked Fallon. “Because he’s so cool and he’s that English thing, you know, that witty. He looks good in a jacket … he’s one of those guys. I love those guys.”

On how he managed to secure the “Regime” star for the film, Seinfeld revealed that Grant actually requested an audition.

“I did not think of Hugh Grant for the part,” Seinfeld noted. “[I imagined] a frustrated Shakespearean actor who has to play this embarrassing character to make his car payments” to make the part work for the Golden Globe nominee, he added.

“But he called us and he said ‘I want to be in the Pop-Tart movie.’ So I got the script and auditioned on my phone.”

“So he did an audition on his phone — with a glass of wine in the other hand, by the way,” joked the actor.

“Like I care what the audition was,” he teased. “I go, ‘Yeah, sure, you’re Tony the Tiger, sure.’” 

In July 2023, Netflix announced that Seinfeld was set to direct, produce and star in the origin film about the breakfast pastry.

The idea came to him from one of his jokes in his 2020 Netflix special “23 Hours to Kill,” where he tells the crowd that “the back of [his] head blew right off” when he first saw Pop-Tarts in a grocery store at the age of 8.

“I was in the supermarket with my mother and I was like, ‘Hold up, hold up — what the hell is that?’ ” Seinfeld recalled. “When you open the packet, there’s two. Why? One’s not enough; three is too many — that’s why. It was perfect. Perfect vision of the future from Kellogg’s.”

The project was further brainstormed during the coronavirus pandemic.

“Stuck at home watching endless sad faces on TV, I thought this would be a good time to make something based on pure silliness,” he told Deadline. “So we took my Pop-Tart stand-up bit from my last Netflix special and exploded it into a giant, crazy comedy movie.”