- Actor-Shared Background: Dennis Franz, like Sipowicz, is a Vietnam veteran.
- Cast the Expert: Consultant and former New York detective Bill Clark was seen a few times as a cop.
- Dueling Shows: with Homicide: Life on the Street
- Real-Life Relative: Lola Glaudini played the squad's secretary, Dolores Mayo. Glaudini's father, Robert Glaudini, played Dolores's father, Jimmy Mayo.
- Unintentional Period Piece: The fact that cars and fashions in the first six seasons are typical for The '90s is not unexpected. However, the show also documents the cellphone revolution: In the first seasons, the detectives don't have cellphones but have to look for payphones if they are not carrying a walkie-talkie. The squad later gets one cellphone that has to be checked out if a detective needs it, and towards the end of the series everybody has their own personal cellphone.
- Writing by the Seat of Your Pants: David Milch did this a lot, often coming up with dialogue right there on set. A number of cast members found this enormously frustrating, with a few even quitting the show as a result.
- You Look Familiar:
- Richard Gant appears a few times as the desk sergeant at another precinct, then later as a municipal bus driver who witnesses a perp running away from the scene of a crime.
- Charlotte Ross appeared in a couple of episodes in season five as a cop's battered wife before returning in season eight as Connie McDowell.
- Silas Weir Mitchell as an abusive boyfriend in one episode, and later as a crime scene witness.
Trivia / NYPD Blue