Nanny 911 is loosely based on the British television programme Little Angels, in which American families with unmanageable children are reformed by British nannies, including one who served for the royal family. A similar show, Supernanny, is its main competitor.
The 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 (though also not always the case). The parents usually have an income that allows them to be upper middle-class.
The introduction features montages of several clips of unruly children (and the nannies' surprised reactions), whereupon stock footage shows a "call" being made to Nanny 911 where "Head Nanny Lilian" (Lilian Sperling, featured as "Nanny to the British Royal Family") answers "Nanny 911" (on an old rotary dial phone).
After the intro the selected family is featured on a separate clip. The video screen is then returned via a rotating device into a standard fireplace picture (performed by an uncredited male who left midway through Season One). Head Nanny Lilian and the other nannies – "Nanny Deb" (Deborah Carroll), "Nanny Stella" (Stella Reid), and "Nanny Yvonne" (originally Yvonne Shove, and a guest star Jo Frost from "Supernanny" would sub in, later replaced by Yvonne Finnerty for unspecified reasons; in Season 4 she will not appear due to budgetary reasons) discuss the clip, whereupon Lilian announces (based on the major need; each nanny specializes in one area, such as proper etiquette or controlling temper tantrums) which nanny will visit the family. The nannies are featured visiting the family in traditional nanny dress (similar to that worn by Mary Poppins).
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; at the end of the day the nanny discusses what needs to be done. The remainder of the week shows the plan being implemented, along with the parents' reactions (which can be quite negative, especially when the nanny mentions how the parents' actions have resulted in the problem). At the end of the week, the nanny generally compliments the family for the changed behavior. The last segment shows the family receiving a substantial gift from the nanny (such as a new car or a home renovation).
After Season Two, the substantial gift portion was removed. In Season Four, probably due to the fact that there were only two nannies, the format changed. Rather than showing a clip to the nannies then deciding which one would go, Lillian just called one of them and sent them to the family. In some episodes this season, the nanny observes for two days instead of just one like in the previous three seasons.
