Jake Johnson, Damon Wayans Jr., Jonathan Lajoie, Rob Riggle and Keegan-Michael Key, who are all stand-up comedians, improvised a lot of their dialogue.
Luke Greenfield got the idea of the film when a costume designer brought him an authentic LAPD uniform to wear for Halloween, which resulted him gaining high confidence.
During one of their first appearances as 'Cops' Damon Wayons Jr. jokes he feels like Danny Glovers character, Roger Murtaugh in Lethal Weapon (1987). His dad, Damon Wayons Sr., would later go on to play Roger Murtaugh in the tv series remake of Lethal Weapon (2016).
Jake Johnson and Damon Wayans Jr. both work on New Girl (2011) together. Nick Miller, Jake Johnson's character on New Girl, has the same surname as Justin Miller, Damon Wayans, Jr.'s character in Let's Be Cops. Rob Riggle has also appeared on New Girl as Big Schmidt.