Emanuel's character has a tattoo on the left arm. The tattoo, are three paws: a dog, a cat and a rat, like a nod to the source material.
Nods to Psycho (spoilers ahead):
Emanuel is doesn't introduced to the audience properly until 30 minutes of the film.
The beginning of the movie shows a day in the job of Dianne, as Psycho does with Marion.
A dinner takes place before a supposed to be main character dies.
As Marion steel the money (a bad action) in Psycho, Dianne does his part reading Emanuel's secret manuscript.
Dianne is inside the bathroom in the murder scene, as well Marion.
Arbogast's character is kinda portrayed by Amayrani Luna, both makes a research to find a missing person, and both get killed when, after two times they revisited the house, they go upstairs.
The "harm a fly" dialogue happens in a mirroring scene in police dept.
During the movie run time, the parts when Emanuel is alone, the soundtrack play songs almost entirely singed by males, and when the main couple appear together, the songs are played by duos (man-woman). Only 5 songs in the movie are played by only woman.
As in the source material, Emen it's not an Emanuel look-a-like double but a cat named Whiskas, in the movie, the character change name to other one that doesn't seem a name for a pet.
"Emen" is a nod to MN, Emanuel's books editorial.
The name was created by joining the name's capital letters from director and main actor: Marco Valdovinos (actor, 'M') and Nicolás de Jesús (director, 'N'), whom were a couple previously before pre production starts.
Unlike the short tale, the story is set on Christmas Eve on 2004, instead the original summer time in 2015.