Nigel Lythgoe has confessed his surprise at the news Simon Cowell is to become a father.
Simon, 53, has confirmed reports that he is fathering his first child with New York socialite Lauren Silverman.
Nigel, who worked with the music mogul on American Idol, was asked on Access Hollywood if he was "stunned" by the news.
Nigel admitted: "Yes, I seriously was. I thought he was a confirmed bachelor.
"I don't think he thought this relationship would go anywhere. It was his best friend's wife. So, I think it came as a surprise to everyone really."
Asked what sort of father he thinks The X Factor boss will make, Nigel joked: "He'll probably tell the kid off, every day. 'You're leaving the house!'."
And he teased the baby would wear: "Nappies just a little too high, little black t-shirts."