The film's working title is "Folie a Deux", which means "Madness of Two" in French. This initially led to speculation about Harley Quinn's appearance in the film, which was shortly thereafter confirmed. The name Folie a Deux comes from the 19th century French psychiatrist Charles Lasègue and Jules Falret, also known as Lasègue-Falret syndrome, and it depicts two or more people that they share the same madness or delirium.
