Parasitic horsehair worms, or Nematomorpha, such as those which infect the victims in the movie do exist, although they only infect arthropods. Two species, Spinochordodes tellinii and Paragordius tricuspidatus, which infect Orthopteran insects, make their hosts drown themselves as depicted in the movie.
In order to create a unique and believable look and feel for the infected, actress MUN Jung-hee worked with a special acting coach to create a set of expressions, movements, twitches, and more. Their hard work was then converted into the basis for rest of the infected cast members' behaviors.