Dennis Franz (Detective Andy Sipowicz) is the only cast member to stay with the series throughout its entire run and the only actor to appear in all 261 episodes.
The character of Detective John Kelly was originally named Flinn and intended for Jimmy Smits, who turned down the role. Smits later played Kelly's replacement, Detective Bobby Simone.
The exterior of the 9th Precinct station house is used to represent the fictional 15th Precinct's station house. It is the same building used to represent the station house on Kojak (1973).
Sharon Lawrence later got married in the same church where her character Sylvia's wedding was filmed.
Prior to the show's premiere and immediately afterward there was enormous controversy over what was perceived to be high levels of offensive language and nudity. Many affiliates refused to air the show and several advertisers boycotted it. Steven Bochco negotiated intensely with the network for a certain amount of language and nudity to be allowed. He has said that because of the pressure on the network from this criticism the show would likely not have survived had it not been an instant hit.
Rick Schroder left the show because he suffered a death in his family and felt he couldn't work properly, so they wrote him out.
Just like an earlier Steven Bochco series, Hill Street Blues (1981), most of the episodes were written to take place over the course of a single day.
The man we see playing the violin just before the closing credits of this show (and most other Steven Bochco productions) is Bochco's father. They computer animated a portrait of him to make it appear he's playing the violin.
According to Steven Bochco, Sherry Stringfield asked the producers to release her from her contract after the first season because she said she was not enjoying being a TV actress and wanted to return to New York. Less than a week after being let out of the contract she was hired as a regular cast member for the new TV series ER (1994). However, in his book "True Blue", David Milch said that Sherry's contract-end request came about because she had very little to do - the prominence of Andy Sipowicz's relationship with Sharon Lawrence's DA took all of the story time that was originally intended for scenes between David Caruso and Sherry - and the request was amiably granted, with Milch also stating he was happy when she got a prominent role on ER.
John F. O'Donohue (Det. Eddie Gibson) was a real-life NYPD detective before retiring to pursue an acting career.
The character 'Andy Sipowicz' was ranked #31 in TV Guide's list of the "50 Greatest TV Dads of All Time" (20 June 2004 issue).
Dennis Franz (Detective Andy Sipowicz) and Gordon Clapp (Detective Greg Medavoy) are the only actors to appear in all twelve seasons.
Despite having appeared on the show since the second season, Scott Allan Campbell's character IAB Sgt. Martens did not get a first name (Jerry) until the twelfth and final season.
The sets on this show of the "New York streets" are on the back lot of Twentieth Century Fox and were originally built for Hello, Dolly! (1969) in 1968. Some location work was actually done in New York City for most of the show's run, mixing specific scenes with general location footage that was used for between-scenes and opening-credits sequences. By the last few seasons, however, the combination of high costs for location filming and the show's reduced ratings meant that 100% of filming was done in Los Angeles.
The footage of the Chinese parade (dragon, fireworks, drums) that's shown in the opening credits was used in the opening scenes of Year of the Dragon (1985).
Before joining the cast as Detective Connie McDowell, 'Charlotte Ross' appeared in the fifth season as the abused wife of a cop suspected by Simone and Russell of killing a prostitute. When 'Andrea Thompson' left the series, producer Steven Bochco remembered Ross and wrote the part of McDowell for her.
Before joining the cast as Lt. Thomas Bale (2004-2005 season), Currie Graham appeared in the fourth season (episode title "Emission Impossible") as a street punk murderer.