At more than 30 years old, the Law & Order universe seems to have always been with us. Revolutionary when the mothership show (also known as "original recipe") premiered in 1990, Law & Order debuted in an era when cable was still a baby and streaming wasn't even invented yet.

NBC called it quits on the original series in 2010, but Law & Order still goes on in endless reruns. Considered the 36th best show of all time by Rolling Stone, it's probably playing somewhere on your TV right now. But how much do you really know about Law & Order? Here are 20 historical bits about the series and its stars—plus how it had a large hand in helping revitalize New York City's TV industry.

1. Law & Order creator Dick Wolf got his start writing ad copy.

Franchise creator Dick Wolf made his screenwriting bones writing films like School Ties and episodes for series like Miami Vice and Hill Street Blues, but he actually came from an advertising background. Before he left the ad world in the mid-1970s, Wolf had penned such legendary ad lines as "You can't beat Crest for fighting cavities" and National Airlines's controversial "I'm Cheryl; Fly Me."

"I turned 30 and realized I didn't want to sell toothpaste for the rest of my life," Wolf said in Law & Order: The Unofficial Companion.

2. Law & Order star S. Epatha Merkerson set a TV record for a Black actor.

S. Epatha Merkerson attends SCAD aTVfest 2020.Vivien Killilea/Getty Images for SCAD aTVfest 2020

S. Epatha Merkerson first appeared on Law & Order as a guest star in season 1 (more on that below), then was hired full-time in 1993 to play Lieutenant Anita Van Buren, who bossed around every homicide detective in the 27th Precinct until the series concluded in 2010. She appeared in 395 episodes over 17 consecutive seasons—and today holds the record as TV's longest-running Black female character in primetime. Until 2017, she held the record for TV's longest-running Black character in primetime—until Law & Order: SVU star Ice-T began his 18th season on the spinoff.

3. Chris Noth was not a shoo-in for the part of Detective Mike Logan.

Though the actors who ultimately got hired in the key original roles will forever live in our memories as the only true possibilities, it turns out that future ER hunk Eriq La Salle was up for the role of ADA Paul Robinette (the part eventually went to Richard Brooks), and future Reservoir Dogs star Michael Madsen was being considered for Detective Mike Logan (which ultimately went to Chris Noth).

According to Inside Television Producing, which features a detailed look at the early production process for the show, Madsen was seen to have "great sex appeal," but was not considered a good combination with George Dzundza, who played Sergeant Max Greevey during Law & Order's first season. Noth was, by contrast, a more "compatible choice."

4. Law & Order’s original district attorney only appeared in one episode.

Roy Thinnes was cast as Alfred Wentworth, the show's original district attorney, who appeared in Law & Order's pilot episode (which ultimately was aired as its sixth episode). But there was such a lag between when the pilot was shot and when the show was ultimately picked up that Thinnes had already been contracted to another series and couldn't reprise the role.

With Thinnes out, original Mission: Impossible cast member Steven Hill was hired as DA Adam Schiff; he remained with the show for 228 episodes (plus one episode of SVU), departing in 2000. Hill, who died in 2016 at age 94, was an Orthodox Jew who would not film on the Sabbath, so his scenes had to be worked around that schedule.

5. NBC wasn't the first—or even the second—network Law & Order’s creators pitched.

The show's first episode was originally shot in 1988, with CBS as the intended airing network. (Fox had been considered at one point, then discarded when then-network head Barry Diller declared it "wasn't a Fox show," according to the Unofficial Companion.)

That pilot episode, written by Dick Wolf and titled, "Everybody's Favorite Bagman," was meant to look documentary-style gritty, and so was shot on 16mm film, then blown up to 35mm, which made it look like nothing else on TV. But there were ongoing technical and audio issues, and in the end CBS didn't pick the pilot up. Wolf was liked at NBC thanks to his work on Miami Vice and Hill Street Blues, so then-network president Brandon Tartikoff ordered 13 episodes of Law & Order for their fall 1990 schedule—two years after the pilot was shot.

6. Law & Order had tons of crossover appeal.

Law & Order creator Dick Wolf and Chris Noth celebrate the 100th episode of Law & Order: Criminal Intent in New York City in 2006.Scott Gries/Getty Images

Naturally the show's cast crossed over with other series in the L&O franchise, but Wolf's close friendship with Homicide: Life on the Street showrunner Tom Fontana led to three extra-franchise crossovers of cast and story: "Charm City"/"For God and Country" (1996); "Baby It's You" (1997); and "Sideshow" (1999). In addition, L&O's Detective Logan (Noth) put in a cameo on Homicide's "Law & Disorder" (1995) episode, escorting a fugitive back to Baltimore. That scofflaw? Legendary director and Baltimore native John Waters.

7. Dick Wolf's union deals brought production in New York City back to life.

To Wolf, there was no question that Law & Order would shoot on location in New York City. But in 1988 (and to some extent in 1990, when production truly began), the Big Apple had almost no television production going on. Unions had longstanding rules in place that made sense for feature films to shoot there, but weren't practical or affordable for television series. So Wolf went to the union heads and had what he described to me in 1997 as a "major meeting ... I think the phrase I used was, 'Hey guys, 90 percent of the wealth is better than no bread at all.'"

The unions agreed to some work rule concessions (the show wasn't charged a location fee for the first four seasons, for example), which made shooting in New York still a bit of a premium, but affordable enough that the show's budget could handle it. By 1997, Wolf estimated that Law & Order alone had dropped about $200 million back into the city. The concessions led to a renaissance in television production in and around the city that continues to this day.

8. Guest roles on Law & Order sometimes turned into permanent gigs.

Going from guesting on the show to returning as a regular, new character happened more than once: S. Epatha Merkerson guested in "Mushrooms" in 1990, then returned in 1993 as Lieutenant Anita Van Buren; Jerry Orbach first appeared as an attorney in 1991's "The Wages of Love," then signed on as Detective Lennie Briscoe in 1992; and Jeremy Sisto appeared in 2007's "The Family Hour" and came back the following year as Detective Cyrus Lupo.

9. Some Law & Order guest stars returned so frequently they were called "repeat offenders."

Since Law & Order drew on a New York-based casting pool, it was inevitable that actors would show up on multiple episodes as entirely different characters. Fans created a "Repeat Offenders" website, attempting to list every actor's name and appearance, which still exists online today (though it hasn't been updated since 2004).

10. Law & Order wasn't a critical darling.

Law & Order stars Sam Waterston and Jerry Orbach arrive at the 52nd annual Primetime Emmy Awards in 2000.Kevin Winter/ImageDirect/Hulton Archive via Getty Images

Though the show aired from 1990 to 2010, it wasn't exactly Emmy catnip. L & Order won six Emmys in its lifetime, four of which were for technical categories like cinematography and sound editing. Only one performer won an acting Emmy: Elaine Stritch for 1993's "Point of View." The series only earned the Outstanding Drama Series award once, in 1997.

Consolation prize: It did win five Golden Globes for Best TV Series drama, and stars Michael Moriarty (Executive Assistant District Attorney Benjamin Stone) and Sam Waterston (Executive Assistant District Attorney Jack McCoy) won Globes for their performances in 1994 and 1995, respectively.

11. Some Law & Order long-termers were there for the whole run … and beyond.

Four people have credits in every single Law & Order episode: creator Dick Wolf, head of post-production Arthur Forney, composer Mike Post, and voice-over narrator Steve Zirnkilton. Zirnkilton's voice kicks off almost every episode of the show with these lines:

"In the criminal justice system, the people are represented by two separate yet equally important groups: The police, who investigate crime, and the district attorneys, who prosecute the offenders. These are their stories."

The opening was changed just once, post-9/11, and for a few episodes became:

"On September 11, 2001, New York City was ruthlessly and criminally attacked. While no tribute can ever heal the pain of that day, the producers of Law & Order dedicate this season to the victims & their families and to the firefighters and police officers who remind us with their lives and courage what it truly means to be an American."

Zirnkilton even appeared in one episode—"Everybody's Favorite Bagman," the pilot episode—and had one line of dialogue.

12. A character's departure didn't always mean the end of their life of Law & Order.

Law & Order players and former players were often tasked with helping spin-offs get off the ground, which meant Dann Florek (Captain Donald Cragen) was able to reprise his role on Law & Order: Special Victims Unit in 1999, and Chris Noth was able to bring Detective Logan to Law & Order: Criminal Intent in 2001. Florek left SVU in 2015 and Noth departed Intent in 2008.

13. Even beloved regulars were killed off of Law & Order (whether they knew it or not).

Law & Order co-stars Benjamin Bratt and Jill Hennessy in 2004.Evan Agostini/Getty Images

Over the course of the show's 20 seasons, three major characters died in the line of duty: Sergeant Greevey (Dzundza) was shot; ADA Alexandra Borgia (Annie Parisse) was kidnapped, beaten, and choked on her own vomit; and ADA Claire Kincaid (Jill Hennessey) was killed by a drunk driver.

Though Greevey and Borgia's deaths were immediately made obvious, Kincaid's departure wasn't so clear. Hennessey exited the show in 1993, but Kincaid wasn't confirmed as dead on the show until 1999. "I found out they killed me off from a friend who watched the show and told me, 'Jill, they said you were dead!' I was surprised, because I always thought I would return," Hennessey told TV Guide in 2009. "Even now, I'd love to come back for some bizarre flashbacks."

14. The relatives of Law & Order regulars were sometimes used as guest stars and stand-ins.

In 1996, Hennessey's twin sister Jacqueline subbed in for her during some scenes in the episode "Corpus Delecti"; Jill was in Baltimore at the time, shooting scenes for a Homicide: Life on the Streets crossover, and couldn't be there to film both shows. Chris Orbach, son of Jerry Orbach, played three different characters on three episodes of the series: "Securitate" in 1993; "Matrimony" in 1997; and "Ambitious" in 1999. From 1999 to 2000, he appeared as Detective Ken Briscoe, Lennie's nephew, during Law & Order: SVU's first season.

15. Law & Order featured dozens of stars-to-be.

The list of young actors who landed some of their earliest roles on Law & Order is a rap sheet longer than your arm, but a few faces you might want to look out for in those reruns are: Sarah Paulson, Laverne Cox, Sarah Hyland, Idris Elba, Philip Seymour Hoffman, Jennifer Garner, Julianna Margulies, Claire Danes, Allison Janney, Laura Linney, Emmy Rossum, Amanda Peet, Courtney B. Vance, Ellen Pompeo, Peter Facinelli, Edie Falco, and Felicity Huffman.

16. There were 465 episodes of Law & Order, which is impressive—but not quite a record-breaker.

Law & Order briefly flirted with breaking the record for longest-running live-action scripted primetime television series; its only competition was Gunsmoke, a show that ran as both an hour-long and half-hour-long series, and ended with 635 episodes. Arguably, Law & Order had more time on air than Gunsmoke, since every one of its 465 episodes was an hour long, but such quibbles were rendered moot in 2019, when Law & Order: SVU surpassed its parent show—and is still going strong today.

17. Law & Order was a spin-off machine.

The Law & Order concept proved so popular that spin-offs began appearing in 1999 with Law & Order: Special Victims Unit, followed by Law & Order: Criminal Intent, Law & Order: Trial by Jury, Law & Order: LA, and Law & Order True Crime. There was also a Law & Order: UK edition, which often repurposed scripts directly from the original series. But the spin-offs haven't finished yet: Law & Order: Hate Crimes has been floated since 2018 with the most recent news suggesting that the series will stream on Peacock, and Law & Order: Organized Crime, which will see Christopher Meloni reprise his SVU character Elliot Stabler, is set to premiere on April 1, 2021.

18. Law & Order's Dun-Dun noise includes the sound of 500 Japanese men stamping their feet.

Call it dun-dun, chung, chung, or thunk-thunk, the iconic Law & Order sound was meant to imitate the sound of a jail cell slamming shut, show composer Mike Post (who created it) told Entertainment Weekly in 1993. It's a synthesized effect that combines about seven different sounds—including the sound of 500 Japanese men stamping their feet on a wooden floor.

"It was a sort of monstrous Kabuki event," Post told the magazine. "Probably one of those large dance classes they hold. They did this whole big stamp. Somebody went out and sampled that."

Bonus: Post, who also wrote the show's theme, gets a separate royalty credit every time the dun-dun sound is used.

19. One of Law & Order's original stars quit by fax.

Michael Moriarty was an original cast member who was with the show from 1990 to 1994. But he was reportedly a challenging performer to work with (in The Law & Order Unofficial Companion, Noth said Moriarty would "kick everybody out of the room and do his take to imaginary people because he didn't want to be distracted by the other actors").

In his later episodes, his behavior became more erratic (Moriarty has struggled with mental illness and alcoholism). Though he was an electrifying presence on the show, Moriarty broke with the series in a dramatic fashion: Incensed that Wolf had met with then-Attorney General Janet Reno, who had expressed concerns about violence on TV, Moriarty sent a fax to show producers declaring "I can't continue," Wolf told The Hollywood Reporter in 2015.

Wolf immediately had Sam Waterston in mind to replace Moriarty; Waterston joined the cast in 1994 and remained with the series until it concluded.

20. Law & Order's real success came in reruns.

Some of the unsung heroes of NBC's Law & Order success story are other networks. Law & Order came into being on the tail end of continuing dramatic stories through series like St. Elsewhere and Hill Street Blues. Those shows were critically-acclaimed and beloved, but didn't do so well in reruns because they relied on continuing story arcs. Wolf purposefully wanted a procedural show that could rerun endlessly, so made sure that very little of the characters' personal lives made it into scripts and that very few episodes linked to one another.

Enter A&E, hungry for something to fill holes in its programming schedules. The cable network began rerunning Law & Order multiple times a day starting in 1995, which boosted the network's ratings plus the ratings of new episodes that aired on NBC—and made the show ubiquitous. Since then, Law & Order reruns have aired on Ion Television, WE tv, TNT, WGN America, and Bounce TV.