This movie was referenced in Seinfeld "The Letter". Jerry's girlfriend cribs a letter from the dialogue in the movie.
It has been suggested that Marsha Mason turned down the role of Jennie in the Broadway production because she couldn't face playing such difficult scenes from her own life night after night on stage. In fact, Mason had just finished The Goodbye Girl (1977) and was enjoying life as Mrs. Neil Simon, making films when they interested her. It is likely that she willingly bypassed the play with an eye on the film version.
"The Taming of the Shrew" poster in Jennie's apartment is from the Joseph Papp production starring Raul Julia and Meryl Streep, whose faces appear on the poster.
Neil Simon once said of his play "Chapter Two" in "The Play Goes On" (1999): "Before I could write the play Chapter Two...I felt I had to go to Marsha to get her consent...If this was too personal to go public with, despite the fact that I would try to give the characters their own personalities separate from ours, I would still have to adhere to her wishes. When I finally asked her, she said, 'It's fine with me because what you'd be telling is your story, not mine. You'd write about what was going on in your head and could only presume what was happening to me. If I want to tell my story, maybe I'll put it in my own book one day.' I was enormously grateful for her consent and encouragement, and although I knew I'd made no promises to her, I would have to treat the story as truthfully as I could."
The play this film is based on is a semi-autobiographical work by Neil Simon, based on his life. Marsha Mason is essentially playing herself, because Simon based the story on their marriage.