Nanny 911 is based on the British television programme Little Angels, in which American families with unmanageable children are reformed by British nannies. Families that are eligible for the show usually have four or more children (though some episodes show homes with fewer children), and the children are usually younger than 9 years of age. The nanny's first day is spent solely in observing the family dynamics in order to determine a suitable plan of action for changing the children's behavior.