- Billing Displacement: The ads only gave Scoot McNairy and Ben Mendelsohn fourth and fifth billing respectively despite their actions driving the plot. The actual film fixes this, as they are billed second and third (though top-billed Brad Pitt still is displaced, as his character doesn't show until more than a half-hour in).
- California Doubling: Set in Boston, but filmed in New Orleans.
- Cowboy BeBop at His Computer: Multiple reviews have claimed the movie's setting has been changed to New Orleans, as opposed to Boston in the source novel; in fact, while the movie was filmed in New Orleans, all indications are that the setting is still meant to be Boston (Frankie refers to Wollaston, most of the characters have distinct Northeastern accents, Mickey refers to going "down to" Maryland).
- Deleted Role: Cameos by Garrett Dillahunt and Bella Heathcote apparently wound up on the cutting room floor; the two had to settle for a "Thanks To..." mention in the end credits.
- Enforced Method Acting: Dominick hid the fact that he planned to rename the film Killing Them Softly so that Pitt wouldn't realize when he was delivering a Title Drop, presumably so he didn't give it undue weight for the scene.
- What Could Have Been: Javier Bardem, Sam Rockwell, Mark Ruffalo and Zoe Saldana were considered for various roles.
- Working Title: Cogan's Trade.
Trivia / Killing Them Softly