The film was shot in chronological order, and the child actors were never shown a script. This was done to elicit the children's authentic reactions to what was going on around them.
The child cast members had zero acting experience, prior to working on this film. They were enrolled in improvisational workshops with an acting coach, prior to shooting.
Over six hundred children were considered, before the child cast members were finalized.
The plush tiger was handmade. Three of them were used in the making of the film. Director Issa López owns the original, a second was kept as a backup in case of damage, and a third was cut into pieces in order to be scanned for the visual effects process.