Kevin Smith and Bruce Willis did not get along well at all on set. Reports surfaced that Willis disliked Smith's direction, felt he didn't interact enough with the cast, and disagreed with Smith's use of marijuana. Smith has counter-claimed that working with Willis was "soul crushing", stating that Willis often refused to listen to direction, was occasionally combative and was generally unpleasant on and off-set.
When Kevin Smith found out the studio was going to lock in the title of the film as "A Couple of Cops" so they could run the trailer behind Sherlock Holmes (2009) Christmas weekend he told a producer, "God that title is going to feel like such a fucking cop out." The producer replied, "We should just call the movie that."
The title is a pun, obliquely referring to being changed from "A Couple of Dicks". That title was itself a pun, with "dick" being 1940s slang for "detective," and was actually spoken by someone in the precinct after the interrogation scene.
Kevin Smith thought of Harold Faltermeyer to compose the score, feeling that the film was an homage to the '80s cop comedy genre and needed one of that genre's most prominent composers. Faltermeyer had retired, but was looking to come back and, after seeing a rough cut of the film, signed on.
After Jimmie and Paul take Gabriella to the Mexican restaurant, Jimmie's arm is shown him wearing a bandage when they're inside the car at Paul's house. That was because a scene in which Jimmie is attacked by an assassin at the Mexican restaurant was deleted.
"Variety" incorrectly stated that the title had been changed from its original one of "A Couple of Dicks" to "A Couple of Cops." Many news sites concluded that the change was a result of the studio disliking the double-entendre nature of the original title. Kevin Smith's previous film, Zack and Miri Make a Porno (2008), had problems with its title as well. It would be changed because no major network would broadcast it before 9:00 pm.
Kevin Smith had been a fan of Bruce Willis for years prior to working with him. Willis, after acting with Smith on Live Free or Die Hard (2007), told him that he was interested in being in one of his films. Despite all this, it was Warner Bros. that suggested casting Willis as Jimmy Monroe.
Tracy Morgan quotes a line from Jaws. Jaws is one of Kevin Smith's favorite movies. He also quotes a line from the Die Hard films "Yipee kay yay mother f...er", which Bruce Willis states he's never seen that. He played John McClane in all the Die Hard films.