Twenty years later and Law & Order: SVU still knows how to make headlines by casting flashy guest stars, as it recently did with Ian McShane and Ariel Winter, who will appear in the first two episodes of the upcoming 21st season.

Landing a guest role on SVU, and on the flagship Law & Order before it went off the air in 2010, is a rite of passage for many actors. And while some are recruited once their career is well underway, giving performers like Mark-Paul Gosselaar and Brittany Snow a chance to showcase a different side of their talents, others are cast when they're still relatively unknown, providing present-day viewers with a sense of gleeful surprise at seeing stars like Paul Wesley and Ty Burrell pop up in the SVU squad room long before they found fame on The Vampire Diaries and Modern Family.

21 Seasons In, Law & Order: SVU Still Feels as Vital As Ever

In honor of SVU's 20th anniversary (Sept. 20) and the kick-off to the history-making 21st season (Sept. 26) — which officially makes it the longest-running live-action TV drama in television history — TV Guide spoke to over a dozen of SVU's past guest stars, including Gosselaar, Snow, Wesley, Burrell, Kyle MacLachlan, Mike Colter, and Gary Cole, about their favorite memories from filming the NBC procedural, what it was like working with Mariska Hargitay, Chris Meloni, and Ice-T, and why the gig is such a dream come true for so many actors. Check out the full video above!

Law & Order: SVU returns Thursday, Sept. 26 at 10/9c on NBC.