* In one episode, Lenny Brisco mentioned that his father was Jewish and his mother was Catholic, while he was Raised Catholic himself, the same as Jerry Orbach's real family background.
* ActorAllusion: Ed Green says he wasn't sure if Joe Fontana was "a cop or a wise guy" when they first met. This referred to Dennis Farina's having played mobsters in ''MiamiVice'', ''Midnight Run'' and ''Get Shorty.''
** Fontana would also frequently mention his days as a Chicago cop. Farina played the lead character in ''Series/CrimeStory,'' who was a cop from Chicago.
*** Also, Farina was a Chicago cop in RealLife before he became an actor.
** Sam Waterston is well-known for his various stage and screen portrayals of UsefulNotes/AbrahamLincoln. Perhaps as a result, Jack [=McCoy=] has at various times suspended ''habeus corpus'' and become deeply involved in cases relating to human trafficking and slavery.
** One episode featured a bitter, paranoid, blind man who blamed his lost vision on the medical profession. The actor playing him was Dana Elcar, who lost his sight while co-starring on ''Series/{{MacGyver}}''.
* CastTheExpert: Attorney and politician Fred Thompson played the district attorney for several years, though he also had prior acting experience playing the roles of senior government officials and authority figures, so this would be a cross between CastTheExpert and TypeCasting.
* ExecutiveMeddling: [[TropesAreTools A strangely positive case.]] You know [[DaChief S. Epatha Merkerson's]] character? How about [[HelloAttorney Jill Hennesey's]]? Both came about via NBC wanting more women on the cast.
* HeyItsThatGuy: ... Be ready to make double-takes once you see who play defendants, prosecutors, etc.
** Agent Coulson plays a victim's boyfriend in the early episode "Life Choice"
** Antwon Mitchell joins the show as detective Kevin Bernard.
** Of course, statistically, there's a damn good chance that any New Yorker has appeared in the background of a Law and Order scene at least once.
** ADA Robinette was [[Series/{{Firefly}} Jubal Early's]] ancestor?
** And how the defense attorney in the Season 18 finale was played by Jeremy Sisto... who joined the series as Cyrus Lupo the next episode.
** Dick Wolf liked to joke that if you go to a play in New York City and a cast member doesn't have a "Law & Order" credit in the Playbill, s/he either just got off the bus or isn't any good.
** [[VisualNovel/{{Clannad}} Tomoya Okazaki]] [[http://www.youtube.com/watch?v=GL_06ojBnfQ is]] a security guard in "Murder Book". Too bad he couldn't use [[SorcerousStabberOrphen magic]] to make Mickey go faster.
** Philip Seymour Hoffman had his first appearance on this show, according to Website/{{IMDB}}. He [[PlayingAgainstType plays a drug dealer and rapist.]] It's a short role, but not as jarring as Creator/SamuelLJackson as a defence attorney. Who doesn't get to kick ass. WhatCouldHaveBeen.
** [[Disney/BeautyAndTheBeast "Be Our Guest"]] takes on a whole new meaning when Briscoe breaks out the handcuffs.
** In the Fourteenth Season episode "3 Dawg Night", the detectives interview the owner of the nightclub where an aspiring hip-hop artist is shot. The owner is none other than IdrisElba.
** [[Series/{{ItsAlwaysSunnyInPhiladelphia}} Mac]] plays a kid who, with another kid, kill's a delivery boy for a [[TitleDrop thrill]].
** [[Series/{{MalcolmInTheMiddle}} Lois]] was threatened with her kid being kidnapped for ending an affair with a judge.
** If you watch the series long enough, you'll probably see loads of extras and minor recurring actors who tend to show up in different roles throughout the series.
* IWantYouToMeetAnOldFriendOfMine: Regina Taylor, who co-starred as Sam Watterson's maid in the critically-acclaimed but short-lived drama ''I'll Fly Away'', appeared in the episode "Virtue" as a lawyer who took the stand against the senior partner who forced her to sleep with him for a promotion, thus getting him convicted of felony extortion. Fans of ''I'll Fly Away'' couldn't help but smile as the two shook hands at the end of the episode.
* LifeImitatesArt: Both Jamie Ross and her actress, Carey Lowell, left for the same reasons: they wanted to spend more time with their daughters.
* MeanCharacterNiceActor: While Lennie Briscoe isn't as bad as most characters in this trope, the real Jerry Orbach was univerally said to be a warm, friendly guy who constantly told jokes, not at all like the dry and [[DeadpanSnarker snarky]] character he made famous.
** He was so well-liked that ''actual'' NYPD officers who spotted him on the streets would often take the time to give him a ride to his destination.
** I'd hardly call Lennie "dry."
* NamesTheSame:
** The judge [[spoiler:who is both senile and being guided by his law clerk]] in Season 19's "Zero" is named [[Series/{{Firefly}} Malcolm Reynolds]].
** One of the victims in Season 2's "The Wages of Love" was named [[Literature/{{Twilight}} Edward Cullen]].
** Crossed with AppealToObscurity: From "House Calls," which is about the death of an aspiring model. Andee Mae Khan, who runs the modeling agency in the episode, talks about how, in modeling, "an inch here, an ounce there" means the difference between (RealLife [=supermodel=]) Creator/{{Elle MacPherson}} and "Cookie Rutigliano." Green asks who that is and the character says, "That's my point." This episode was written by Janis Diamond, who was later one of the writers of the short-lived [=TNT=] series ''Bull,'' which included a character named Cookie Rutigliano.
* ThePeteBest: The original DA was not Adam Schiff, but Alfred Wentworth, who appeared only in the pilot. Ironically, Schiff was played by Steven Hill, who was himself subject to this trope (he was the original lead on ''Series/MissionImpossible'').
* TypeCasting: Jerry Orbach had performed in numerous musicals and other performances prior to his role on the show, playing a detective character only once in a movie. Nevertheless, his performance in that movie impressed Dick Wolf so much that he wanted Jerry to continue with the snarky detective character; because of his immense popularity as Det. Lennie Briscoe, he remains instantly recognizable as his detective character.
** Dennis Farina, as mentioned before, was a cop in the Chicago PD, so he played numerous police roles before and after his stint as Joe Fontana.
* UnderAgeCasting: Jill Hennessy was twenty-four when she was cast as Claire Kincaid. In the United States the minimum age at which one can graduate from law school is twenty-five.
** Not necessarily. If don't take any time off and have a birthday after May, you would graduate at twenty-four (high school graduation at seventeen, college at twenty-one, law school at twenty-four). It's not common, but it's possible, especially if you commit to becoming a lawyer young.
* WhatMightHaveBeen: A particularly tragic case of RealLifeWritesThePlot: In early 2001, Dick Wolf was planning a large-scale miniseries event involving the casts of ''Law And Order'', ''Series/LawAndOrderSpecialVictimsUnit'', and ''Series/LawAndOrderCriminalIntent'' teaming up to investigate a terrorist attack on New York City. Then [[TheWarOnTerror September came along,]] and...
** Less tragically, Detective JustForFun/JohnMunch from ''Series/HomicideLifeOnTheStreet'' was originally pitched as joining the original series as Detective Briscoe's new partner, but by the time the suggestion was made a new character had been created to fill the role, so he was moved to ''SVU'' instead.
** Alana de la Garza's pregnancy would have been written into Season 21 if the show had not been canceled.