Meryl Streep was 29 years old, and this was her first major film. The scene was a marital argument. The script said nothing about a slap.
Dustin Hoffman actually slapped her.

It happened during the filming of Kramer vs. Kramer, in 1979. Streep played Joanna Kramer, a mother who leaves her son and returns to claim him. It was her first take in her first major film. No one warned her what was going to happen.
The slap left a handprint on her face. The set fell silent. No one said anything. No one stopped the camera.
Years later, in an interview with The New York Times in 2018, Streep recounted what she felt that day. She said it was real and that it can be seen in the film.
It was not the only time. In another scene, Hoffman smashed a glass against the wall without warning, and the pieces flew near her.

The film won five Academy Awards, including Best Picture, Best Actor for Hoffman, and Best Supporting Actress for Streep.
Streep and Hoffman never worked together again.
Sometimes the biggest applause hides the wound no one wanted to see.
