That child is going to burn down my house. If I had a cat that child would skin it and leave it on the front porch. That is the reason I will not have children. I will probably never sleep soundly again.

No f-ing wonder that Julia Stiles said she had nightmares while filming The Omen. I'm sure he's perfectly sweet while he is plotting his next demonic move. but there is something more going on with that kid. Either that, or give that kid an Oscar, he certainly is a convincing little devil. As the Denver Post quoted Stiles:

"I had horrible nightmares every single night when we were shooting the film," she recalls. "I guess I tend to internalize things.

"My character is supposed to be very tormented by the whole situation," Stiles continues, "because I play the mother of this boy. She truly loves her son, who happens to be the devil. This mom hides her fears and is afraid to voice them. My character does actually admit, 'Yet, when I close my eyes, I see grotesque things.'

"That line sank into my head," the actress says, "and I started seeing grotesque things at night while I was supposed to be sleeping. It didn't help that my hotel room in Prague was next to the oldest cemetery."

All the stars looked really lovely at the premiere of the film, but I can't really focus on anything because I feel like tat child's eyes are peering into my soul and seeing my demise.

[Source, Source]