The inspiration for the movie and the plot came from true events. Tania and Daniela characters were inspired by Sara Cohen (Salomon Askenazi's wife) and her first cousin and best friend (Also named Sara Cohen). Sara & Sara had such an intense relationship that Salomon thought about doing a movie portraying that union. And once, in a wedding, they tried to play the game of "wife switch" with no success. But it helped to inspire the script.

The dresses that the girls (Melissa Barrera and Anahi Davila) use in the wedding scenes, actually belong to Sara Cohen, the director's wife.

The movie went through an extensive editing period, having 20 different cuts.

When Melissa Barrera (Daniela) came to the first casting, Salomon knew she was perfect for Daniela before she even started acting. Anahi Dávila (Tania) was chosen for the part almost 2 weeks into preproduction.

This is Daniel Adissi's (Benny) first experience as an actor. He had never even cast for anything before. He also helped composing some of the score of the movie, and wrote 3 songs for the soundtrack. He is also a photographer, and some of his work was used to decorate the apartments in the movie.

The role of Tania was originally offered to Sofia Espinosa, she accepted the role but later declined because of schedule complications.

This is Isaac Cherem's first movie as a producer. He later directed his first feature called "Leona" which Salomon produced.

Many titles were used before the final one. "Entre Primas" was used to find funding. The script was titled "The Cohens". Later, some cuts had the title "Prima" and "Tania & Daniela". Finally the right and final title arrived just before the movie was finished.

During the scenes where characters smoke weed, some of them asked for real herb instead of fake herb because it tasted real bad.

The location of each of the apartments of Tania and Daniela is the same. The art department had one week to transform the decoration to get the effect of different locations.