Spinoffs rarely outlive their original series, and they definitely don't eclipse them in terms of longevity. But Law & Order: Special Victims Unit defies expectations. The series, which kicked off just before the millennium and focused on abuse and trauma of some of society's most vulnerable, found its guiding light and voice early on thanks in large part to the full, dedicated embodiment of its lead detective, Olivia Benson (played by Mariska Hargitay).

Law & Order, the show that birthed the franchise, turned out its lights in 2010, but SVU continues to plow forward—and create its own spinoffs. Law & Order: Organized Crime, starring original SVU cast member Christopher Meloni, premiered on April 1 with a crossover into his old stamping grounds before sending his Detective Elliot Stabler off on his own adventures.

Yes, SVU has become a true institution—but are you aware of just what has made it so remarkable and enduring? Here are 15 bits of history that trace its beginnings, its milestones, its awards—and the loose way it plays with canon.

1. You'd need to set aside nearly three weeks to watch all of Law & Order: SVU.

Chris Meloni and Mariska Hargitay on the set of Law and Order: Special Victims Unit in 1999.Jason Green/Hulton Archive/Getty Images

As of April 16, 2021, there had been 477 episodes of Law & Order: SVU, which would take you 19 days and 23 hours to watch back-to-back. The first episode, "Payback," aired on September 20, 1999.

2. Law & Order: SVU’s original leads had a super meet-cute moment.

During her SVU audition, Hargitay had been alerted that future Mad Men star John Slattery would be trying out for the role of Elliot Stabler, a part that ultimately went to Meloni. Hargitay's agent represented Slattery, too, but the two actors had never met. So when she saw Meloni she cried out, "Slattery!" to which he instantly responded "Meloni!" and the two hit it off instantly. When Hargitay noticed Meloni's large religious tattoo, she asked if he was a believer in Jesus. "No, but I admire his commitment," he told her.

3. The crossover appeal was endless … for one Law & Order: SVU character.

Richard Belzer and Kelli Giddish in Law & Order: Special Victims Unit.NBCUniversal Media, LLC

Detective-turned-Sergeant John Munch (Richard Belzer) originated as a character on Homicide: Life on the Streets. He went on to become one of TV's greatest crossover stars, with Belzer guesting as Munch on numerous other series, including The X-Files, Arrested Development, The Wire, 30 Rock, and Unbreakable Kimmy Schmidt. A Muppet version of Munch (portrayed by David Rudman, not Belzer) appeared on Sesame Street's "Law & Order: Special Letters Unit" sketch in 2006.

4. There's one holdover from the original Law & Order.

Steven Zirnkilton has provided the opening narration for every Law & Order show since the franchise's inception. Each episode of SVU begins with him intoning, "In the criminal justice system, sexually based offenses are considered especially heinous. In New York City, the dedicated detectives who investigate these vicious felonies are members of an elite squad known as the Special Victims Unit. These are their stories."

5. Sibling rivalry may have prevented a love connection on Law & Order: SVU.

Olivia Benson and Elliot Stabler are named after two of show creator Dick Wolf's children—which some people believe explains why the two of them have never had a more-than-platonic relationship.

6. Law & Order: SVU was partly inspired by "the preppy killer" case.

Mischa Barton and Mariska Hargitay rehearse scene for Law & Order: Special Victims Unit in 2010.Ray Tamarra/Getty Images

Originally the show was going to be called Law & Order: Sex Crimes, and was inspired by the so-called "Preppy Killer" case: In 1986, 19-year-old Robert Chambers strangled 18-year-old Jennifer Levin in New York City's Central Park. Dick Wolf had written a Law & Order episode that "ripped" from that headline, and saw a future in these kinds of stories. But NBC thought that was a bit too raw for a title. "We're going to be covering a wide range of crimes and Special Victims Unit just seems more inclusive," Wolf told The New York Post in 1999.

7. Law & Order: SVU’s backstories are sometimes confusing and contradictory.

Canon is a bit slippy in the SVU-niverse. While the squad room has always been in the 16th Precinct, Benson's badge number has changed. And in season 1, Benson was clearly shown as being new to the unit, but by season 3 writer Judith McCreary decided that Benson had been a sex crimes detective for seven years. "I'm sure some of the audience pays attention to those details in a very anal way, but we're more interested in the undercurrents and personalities clashing in the workplace," McCreary said in The Law & Order: SVU Unofficial Companion.

8. Law & Order: SVU has featured a number of big-name guest stars.

The show has been a hotbed of name actors and aspiring thespians, all of whom have wanted their moment in the SVU spotlight. Some of the celebrities who've had to face off with the detectives and lawyers are: Bradley Cooper and Angela Lansbury ("Night"); Robin Williams ("Authority"); Milo Ventimiglia ("Escape"); Carol Burnett ("Ballerina"); Patricia Arquette ("Dreams Deferred"); Jerry Lewis ("Uncle"); Serena Williams ("Brotherhood"); and Elle Fanning ("Cage").

9. One Law & Order: SVU showrunner likes embedding Easter eggs.

For its first 12 seasons, SVU episodes were one-word titles. But when showrunner Warren Leight signed on from seasons 13 through 17, the titles began growing longer. When he came back in season 21, he picked up where he left off with longer episode titles. What gives? Well, it turns out for every season he's been on, the number of letters in any episode title corresponds with the season number.

10. Mariska Hargitay suffered an on-show injury.

While filming a scene in late 2008, Hargitay—who has been doing most of her own stunts since she began filming SVU—took an accidental tumble that left her with a partially collapsed lung. In January 2009, she underwent surgery to repair the lung and returned to work shortly thereafter, missing just one episode of filming. But on March 3, 2009, she checked back into the hospital complaining of discomfort in her lung. After undergoing some routine tests, she was able to report back to work less than three weeks later. In May, she told People "I'm 100 percent. I'm back to my old self."

11. Taylor Swift is a noted Law & Order: SVU fan.

Taylor Swift performs onstage with actress Mariska Hargitay during The 1989 World Tour on June 13, 2015 at Lincoln Financial Field in Philadelphia.
Dimitrios Kambouris/LP5/Getty Images for TAS

In 2014, Taylor Swift was a stan for SVU, announcing she'd named her new Scottish Fold cat "Olivia Benson." Hargitay and Swift eventually became pals; they met at the famous Met Gala, and Hargitay later appeared in Swift's video "Bad Blood."

12. Law & Order: SVU guest stars have made out better in the awards department.

SVU has 23 Emmy nominations, and six wins—though only one was given to a regular cast member. Hargitay picked up an Emmy for Outstanding Lead Actress in 2006. The other awards were given to guest actors Amanda Plummer (2005), Leslie Caron (2007), Cynthia Nixon (2008), Ellen Burstyn (2009), and Ann-Margaret (2010).

13. Friends and family members of Law & Order: SVU’s stars have been welcomed into the fold over the years.

Over the decades, SVU has hosted many relatives of its stars, among them Hargitay's dad, Mickey Hargitay, and Ice-T's wife, Coco Austin. Peter Hermann met Hargitay when he dropped in for a guest visit in 2002; the couple married in 2004 and have three children. Hermann has appeared on the show 33 times in total, as defense attorney Trevor Langan.

14. Mariska Hargitay took her SVU role to heart in more ways than one.

Though she had several acting roles before signing on to SVU, Hargitay found her life's calling with the series—not just in the stories, but in the real-life horror stories that inspired them. In 2004 she formed the Joyful Heart Foundation, which helps survivors of sexual assault, domestic violence, and child abuse. In 2010, Hargitay went before a House judiciary subcommittee to discuss the backlog in rape kits (a topic also covered on the show). She has also been trained as a rape crisis counselor.

15. Law & Order: SVU continues to set records and break barriers.

Ice-T and Peter Scanavino in Law & Order: Special Victims Unit.Michael Parmelee/NBCUniversal Media, LLC

On September 26, 2019, SVU became the longest-running primetime TV drama in history with its season 21 premiere episode. Meanwhile, Hargitay's Benson is the longest-running primetime drama character ever on U.S. television, and Ice-T's Odafin Tutuola is the longest-running Black character on primetime TV.