Director Clarence Brown was so overawed by the developing romance between Gilbert and Garbo that at the end of one particularly passionate scene he did not even call "cut," instead motioning the lighting and camera crews to stop filming. They withdrew from the set and, after a few hours, had dinner sent in.
During the "cigarette lighting" scene in the garden, the "match" cupped in Leo's hand is actually a very small carbon arc lamp built for the scene - very hot, very dangerous, but providing a remarkable visual effect.
The film's female lead Barbara Kent, and its co-writer Frederica Sagor Maas both lived to be over 100. Kent died on October 13, 2011 at the age of 103 whereas Sagor Maas died on January 5, 2012 at the age of 111, making her one of the few supercentenarians well known for reasons other than longevity.
The first scene between John Gilbert and Greta Garbo, in the train station, was also the first time Gilbert ever saw Garbo. He falls in love on camera, so completely in love that he never went back home to his wife.
The role of Felicitas was first conceived for Lillian Gish, but at the time she was getting $1 million per picture. The role was assigned to the recently-hired Greta Garbo, who was contracted at $450/week.
According to Barry Paris's commentary on the 2005 DVD release, Garbo initially refused to do this film, which was scheduled for production immediately following her last picture, and also not long after the death of her sister from cancer. MGM sent her a sternly worded telegram, and she capitulated.