'Law & Order: SVU' - 400 episodes and counting

NBC News – (NBC) "Law & Order: SVU" marks a television milestone tonight.

The venerable police drama will air its 400th episode.

Hargitay's not only still on the job as Detective Olivia Benson after all these years, but also did double-duty as the director for the 400th episode.

"Mariska sets the example and everybody follows it, and that's why the show's been on for so long and doing so well for so long," says co-star Peter Scanavino.

Episode 400 comes in the midst of the 18th season. Only two live action series have lasted longer, the original "Law & Order" and "Gunsmoke". Each ran 20 seasons.

The longevity goes beyond what longtime cast members ever expected.

"I only came to do four episodes. And here I am, 18 years later," laughs Ice-T.

He says once he was "all in" on "SVU", his goal was to do 365 episodes. That way, fans could watch a different one every day over the course of a year.