Leslie Mann was so convincing during an argument scene with Paul Rudd that he became convinced she hated him.
The couple played a warring married couple in Leslie's husband Judd Apatow's movie 'Knocked Up' and Paul admitted he was slightly scared by how convincing Leslie was.
He said: "She's so good and gets so intense and into it that I remember thinking the next day 'She hates me, she totally hates me."
However, after Paul revealed his insecurity to another castmember Leslie reassured him.
He explained: "She said, 'I don't hate you at all, I hate Judd.' "
The couple teamed up again for the movie's sequel 'This Is 40' and Paul compared their off screen relationship to that of siblings because they get on so well.
He added to US Elle magazine: "I adore Leslie and we are great friends - brother and sister is not that far off from a description of our relationship or husband and wife who've been married a long time."