Most 21st birthdays are a cause for celebration, but that’s especially true for the cast and crew of Law & Order: Special Victims Unit.

When NBC’s long-running procedural returns on Thursday night, it will kick off a historic season that pushes it past the original Law & Order and Gunsmoke to make it the longest-running prime-time drama ever.

So, it goes without saying, the stakes are higher this year for the squad, and not just the ones on screen. “I couldn’t be more excited. You don’t remember your 19th birthday, but you remember your 21st,” says returning showrunner Warren Leight, who previously worked on seasons 13-17. “You always take it seriously but you have to figure out, how is this season different than any other season?”

The show plans to waste no time honoring that milestone: “Right at the top of the first episode, we tip our hat to Gunsmoke. We have a little wink to that show.” And, as Leight hints, there’s “a lot of change coming” for Sgt. Olivia Benson (SVU mainstay Mariska Hargitay) and the squad as a whole. “There’s changes in the squad room, there’s changes in the DA’s office. There’s a lot in motion. And so her task is to redefine roles for everyone on her team, for herself, and for her son.”

Which brings us to the question of the ADA, a position currently vacant following the departure of Peter Stone (Philip Winchester) at the end of last season. Don’t expect a new full-time face to show up right away — per Leight, there won’t be a “full-time Barba or Stone” sort of character immediately joining the team, which means we won’t spend a lot of time in the courtroom at the start of this season. (Instead, think more squad room and time in the field.)

Things also start off with a high-profile guest star in Ian McShane, playing a “big villain” in the form of a predatory Hollywood mogul type. “That’s a larger than life character that our guys need to grapple with, because too many of those kinds of guys have gotten away with it in the past,” Leight notes. Modern Family star Ariel Winter appears in the show’s second episode, an “intense, emotional” installment in which she plays a victim who has no memory of her assault, and the week after that will feature a character who’s faked an assault against himself “for his own hard-to-fathom reasons.” It’s all part of the bigger picture Leight has in mind for this record-breaking season. “There’s people grappling with major moments in their life — maybe operatic is too big a word, but you want large themes for each episode and large themes for the season. You don’t want just, ‘the guy did this, then we caught him.’”

If you’re a longtime fan hoping some favorite faces from SVU‘s past may appear over the course of such a high-profile season, you’re probably not alone — and won’t be disappointed. Leight says he doesn’t want to make the whole season a nostalgia trip, but we’ll see “a few” returnees come through (no word on exactly who, though, so keep saying your prayers to Saint Stabler). And while recent years have included crossovers with Law & Order mastermind Dick Wolf’s stable of Chicago shows, Leight might be looking a little closer to home: “I want the Brooklyn Nine-Nine crossover,” he joked. “That’s the one I want.” Somebody get Peralta on the line!

Law & Order: Special Victims Unit returns Thursday at 10 p.m. on NBC.

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