- Actor-Shared Background: Tracy Spiridakos is Greek like her character, Hailey.
- Backed by the Pentagon: This show is produced with the cooperation of the Chicago Police Department, meaning that they have permission to use accurate uniforms, insignia, and markings. The real Chicago PD is extremely selective about who it gives such backing to. Chicago PD is only the second projectnote since The Blues Brothers to receive permission.
- Fake Mixed Race: Rojas mentions that she's an Afro-Latina, implying that one or both of her parents are black. Both of Liseseth Chavez's parents are of El Salvadoran heritage with no indication of being mulatto, making the actress herself Ambiguously Brown at best.
- Fake Nationality: Greek-Canadian Elias Koteas as Polish-American Olinsky.
- Hide Your Pregnancy: Burgess' move from patrol to Intelligence, accompanied by a looser-fitting wardrobe and a lot of time sat at a desk, coincides with Marina Squerciati's advancing pregnancy. When Squerciati went on maternity leave, Burgess was written off for a time by helping her sister Nicole recover after being assaulted.
- Hostility on the Set: Erin Lindsay's departure from Intelligence was the result of Sophia Bush not renewing her contract, citing an inhospitable work environment due to the Chicago weather and "a constant onslaught barrage of abusive behavior". As stated below, Jason Beghe's anger management issues were a driving force behind her decision, given that their characters often interacted closely but she also clarified that she had raised her concerns to the producers numerous times only to be blown off as she'd signed a seven season contract. She was finally allowed to leave after Season 4 after putting her foot down and giving the producers the choice of letting her do so quietly or risk her suing the network.
- Reality Subtext: The revelation of a real life "black site" kept by the Chicago Police Department to detain (mostly minority) suspects indefinitely without due process has many people looking at the main cast poorly. Not to mention the existence of Jon Burge, a high ranking Chicago police detective who was convicted of torturing many (mostly black) suspects into falsely confessing to crimes.
- Screwed by the Network: This show's third season had to be reworked to conclude Chicago Fire's third season cliffhanger after Fire was delayed by NBC to make room for Neil Patrick Harris' new variety show. The showrunners weren't happy.
- Troubled Production: Jason Beghe began demonstrating serious anger management problems that disrupted production, prompting counselors being hired to help him keep his temper under control on set. Beghe's anger issues were the driving force behind Sophia Bush's departure.
- What Could Have Been: The show had an entirely different cast and setting when it was being developed during Chicago Fire's first season. In fact, the only characters to make it to Chicago PD's first proper episode were Voight, Dawson, and Wilhite and Wilhite is immediately killed off. A good chunk of the parent program's second season had to be used to introduce the revamped cast before PD's first proper episode.
- Word of Paul: Fans thought a conversation between Bunny and Voight at the end of "Erin's Mom" was The Reveal that Voight is Lindsay's biological father. Sophia Bush had to take to Twitter to explain, no, Voight is NOT Lindsay's biological father.
Trivia / Chicago P.D.