Robert Downey Jr. "hated" his 'Restoration' co-star Hugh Grant.
The two men worked together on the 1995 drama but the British actor claimed the 'Iron Man' star took an instant dislike from the moment they first went on set together.
Hugh recalled: "He hated me. He took one look at me and wanted to kill me."
Fortunately for the 57-year-old actor, he hasn't had such bad experiences with his other co-stars.
Hugh hailed his 'Sense and Sensibility' and 'Love Actually' co-star Emma Thompson as a "genius".
But he added: "She is not remotely sane. She's nuttier and nuttier as the years go."
And he thinks 'Bridget Jones' Diary' actress Renee Zellweger is equally "nutty", but they get on very well.
Speaking to People Editor-in-Chief Jess Cagle, he said: "Renee loves me and I love Renee. Well, I mean she's in the same category as Emma Thompson, in terms of lunacy, but an amazing actress of course, and very generous."
However, the 48-year-old actress almost got him into trouble when she sent a saucy gift.
He recalled: "She once sent me a fabulous huge volume of beautiful photography, including a lot of semi-undressed women. I remember it because I had just landed in Marrakesh ... and the book was impounded."
Like Emma, Hugh - whose girlfriend Anna Eberstein is pregnant with his fifth child - thinks his 'Florence Foster Jenkins' co-star Meryl Streep is a "genius", but he did have some problems when working with her.
He explained: "She doesn't see very well, but she refuses to wear contact lenses. The result is, if we're doing a scene, I could have been Denzel Washington."