Variety incorrectly stated that the title had been changed from its original name "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. The title would up being changed anyway, due to major networks refusing to promote it before 9 P.M.
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."
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 one of his films. Despite all this, it was Warner Bros. who suggested casting Willis as Jimmy Monroe.
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 personally 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 the genre's most prominent composers. Faltermeyer was previously in retirement, but was looking to come back, and after seeing a rough cut of the film, signed on.
Kevin Smith and Bruce Willis did not get on well at all on set. Willis was really annoyed at Smith's lackadaisical approach to directing, not interacting with his performers and generally smoking too much marijuana.
After Jimmie and Paul take Gabriella to the Mexican restaurant, Jimmie's arm shows him wearing a bandage on his arm when they're inside the car at Paul's house. There is a deleted scene where he is attacked at the restaurant bathroom by an assassin.