The director of Past Lives needed star Greta Lee to be a little bad at speaking Korean

polygon.com:

Past Livestakes place across time and countries — and languages. Nora, the character at the center of A24’s acclaimed new drama, switches between her native Korean and the English she’s spoken since she was 12 years old. It is firmly a bilingual film.

Crafting a bilingual movie means accepting that the nuances of its language will probably be lost on most of the audience, writer-director Celine Song tells Polygon. Nevertheless, she took great care in guiding her actors to find the right way to speak in both of the languages, to make sure that the way they pronounced words made sense for their characters.

The movie follows two childhood sweethearts, Hae Sung (Teo Yoo) and Nora (Greta Lee), over the course of their lives, revisiting them in 12-year increments. The two part ways in their youth, when Nora’s family immigrates to Canada; reconnect in their young adulthood, only to part ways again due to the strain of a long-distance connection; and in the present day, Hae Sung visits a married Nora for a couple of days in New York City.

In one of the film’s most memorable scenes — the scene that picks up what the enigmatic introduction teases — Nora sits at a bar with Hae Sung and Arthur, and translates for them. Arthur is learning a little bit of Korean and Hae Sung is passable with his English, so they do manage to have one conversation together when Nora is in the bathroom. But otherwise, each of the men waits as Nora talks to the other, unable to understand.

In real life, Yoo speaks English, and the actors were told what the dialogue was. So, figuring out just how Hae Sung and Arthur speak in their non-native tongues, and how they react to what’s being spoken around them, added a new layer to the acting and directing