In the novel upon which the movie is based, Nell's surname is Munro. This was changed to Forbes after Marilyn Monroe was cast in the role.
The screenplay was written by Daniel Taradash, based on the novel Mischief by Charlotte Armstrong, published in 1951. It was first serialized in Good Housekeeping Magazine from April 7th to May 7th, 1950.
The patent pending camera process was, of course, modeled after the first incarnation of the Polaroid instant camera, which debuted in 1948.