In just four weeks, “Denominación de Origen,” the second feature from Chilean director Tomás Alzamora (“La Mentirita Blanca”), has gone from a modest regional comedy screening in a handful of theaters to a full-blown national cinematic phenomenon.

With over 40,000 admissions sold and counting, this not-quite docu-comedy has far exceeded expectations, both commercially and culturally, becoming one of the most-watched Chilean films of the year. And the small-town-set story has done so without a major marketing campaign, with a diminutive budget and with non-professional actors.

In its first week, “Denominación de Origen,” produced by Alzamora and his long-time producer Pablo Calisto at their label Equeco, drew 10,000 admissions across just 29 theaters. By the second week, it not only maintained momentum, but it grew: 15,000 new admissions and an expansion to 37 theaters. In its third week, with 49 theaters nationwide, the film held steady with another 15,000 viewers, totaling 40,000, making it the second-most watched Chilean film...