The movie was shot in 22 days.
In a press conference after the end of the filming, in February 2014, producer Álex de la Iglesia was asked about a possible release date. He answered that probably would be before or after Christmas, but definitely wasn't a movie to release during Santa Claus' days. Ironically, the movie finally was released on Christmas Day of that year.
The movie was presented at the International Film Festival 2015 in Panama.
As a reason for its release in Spain on Christmas Day, directors released a teaser some days before in which appears Montse from behind in a dark room candle lit singing "Silent Night". The camera surrounds her until she is facing it, discovering that she is cover in blood.
The plot takes place in January 1950, not clear if during days 8 to 12 or during 9 to 13.