They'll go crazy on you

"The Hand That Rocks the Cradle" (1992)

The lady: Peyton Flanders (Rebecca De Mornay)

The crazy: Nannies bring a sense of comfort to parents. Take the charming Flanders (De Mornay) for example. She conceals her identity to exact revenge upon the Bartel family, who she blames for her husband’s suicide. Nanny 911, indeed.