Every culture has stories about ghosts. In the mid- to late-1800s, a movement called Spiritualism gained popularity in English-speaking countries. It was based on the belief that the disembodied spirits of the dead could communicate with the living and, at times, advise them. Europe and America in the mid- to late-1800s saw a golden age of classic ghost stories, including works by Edgar Allan Poe, Nathaniel Hawthorne, and Ambrose Bierce in the US, Henry James and Charles Dickens in England (Dickens’s A Christmas Story famously contains the ghosts of Christmas Past, Present, and Yet to Come), and others. During the 1900s, movies and TV shows told ghost stories, from the friendly spirits of Topper, The Ghost and Mrs. Muir, and Casper the Friendly Ghost to the horror of The Haunting of Hill House and the Nightmare on Elm Street film series.

A principal plot device in ghost stories is that only some people, often children, can see supernatural beings. Bod’s tale is an example of this formula. It plays on the idea that children concoct imaginary friends to play with, raising the possibility that those friends might be real, but invisible to adults. Indeed, Scarlett’s parents believe that Bod himself is imaginary.