* FakeAmerican: Canadian Creator/DonaldSutherland plays Klute.
* MethodActing: To prepare for her role as Bree, Creator/JaneFonda spent a week in New York City observing high-class call girls and madams; she also accompanied them on their outings to after hours clubs to pick up men. Fonda was disturbed that none of the men showed interest in her, which she believed was because they could see that she was really just an "upper-class, privileged, pretender". Eventually, Fonda turned to her memories of several call girls she had known while living in France, all of whom worked for the famed Madame Claude. All three had been sexually abused as children, and Fonda used this as an "entry" to her own character, and as a way to understand Bree's motivations in becoming a sex worker.
* RomanceOnTheSet: Creator/JaneFonda and Creator/DonaldSutherland developed a nonexclusive romantic relationship offscreen which lasted until about June 1972. He was her date to the Oscars when she won Best Actress for this movie.
* ThrowItIn: The scene with the psychiatrist was mostly ad-libbed. Pakula used just one camera and later said he should have used two as Vivian Nathan's reactions were much more interesting in the takes where the camera focused on Creator/JaneFonda.
* WagTheDirector: In the original script Bree's psychiatrist was male but Creator/JaneFonda felt in rehearsals, that the character would never open up to a man so she requested that the part be changed to a woman. Fonda requested to shoot the scenes with the shrink at the end of shooting so she would have already fully internalized the character of Bree.
* WhatCouldHaveBeen:
** Creator/JaneFonda had doubts about whether she could portray the role and asked Alan Pakula to release her from her contract and hire Creator/FayeDunaway instead, but Pakula refused. Creator/BarbraStreisand was offered the role.
** Creator/GeneHackman and Creator/PaulNewman were considered for John Klute.
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