One of the shooting days a bear and its cub came down the mountain and remained outside the location for a couple of hours. During that time the crew couldn't go out to take a smoke and were not allowed to leave the location.
The art department had to do a research and ran several test to get the final look of the beverages and cocktails.
The only role for which casting auditions were held was the one of the sister of the leading character. Adelaida Cortés won the part. Oscar Rodríguez Górriz personally offered the rest of the roles to actors that he already knew and that he envisioned for the parts.
Part of the budget was risen by crowd funding.
Several test were made order to create the blood for the withe room scene. The main concern was the safety of Ana Ochoa and at the same time to be able to get the right texture for the blood because it was going to be shot in slow motion. Some of the mixtures that were test included: milk with colorant, tomato puree with flour, honey and natural paint, juice powder with cherry soda, and several mixtures of them. The final mixture that was used was water with juice powder and flour.