NCIS’ Longest-Running Castmember Sean Murray Says His Fate on the Show Is Uncertain: ‘You Never Know’ (Exclusive)

Despite being the longest-running cast member, Sean Murray doesn’t quite feel safe in his standing on NCIS.

As the crime fighting franchise gears up to hit 1,000 episodes across its five shows, Murray, 46, exclusively tells PEOPLE that “even after 21 seasons” he doesn’t know where his journey on NCIS will lead.

“I think we learned this with things that have happened on the show over the years… No one is quite safe,” he explains. “Obviously, being here 21 years, [I] have enjoyed, immensely, being a part of this show and continue to be incredibly grateful to be a part of this show, but you never know what’s going to happen.”

Though the actor doesn’t want to say “anything’s for certain,” he says things are “really good right now” and the cast is having a “good time” on set.

“And I don’t think anyone is itching to go elsewhere at the moment,” he says.

On Monday, April 15, NCIS will be celebrating its 1,000th episode. While reflecting on why he believes the franchise has endured, Murray reveals that he believes the “quality” and care put into building the procedural had created a strong foundation for the NCIS brand to grow.

“A really strong ship was built very early on, and the show developed and founded strengths in a different kind of way than most procedurals,” he says, adding that fans connected with the show and its characters “early on.”

He continues, “It felt like a family, and I think that that family feeling and the world of NCIS is something that people really liked to be a part of.”

Though Murray can’t put an exact finger on the franchise’s “secret sauce” for success, he says that formula has spread out to different series. Since the OG NCIS debut on CBS, the show has gone on to birth four spinoffs in Los Angeles, New Orleans, Hawai’i and Sydney, Australia.

“Everyone, respectfully, has had their own sort of slice of the pizza,” he explains of how the franchise has grown. “Everything’s been pretty unique, I think, so it’s really quite cool to see the way things have expanded.”

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NCIS airs Mondays at 9 p.m. ET on CBS.