NCIS has been part of the CBS primetime lineup for 18 seasons, with the network airing more than 400 episodes.

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[{"selector":"#anim-9b1a4201-5eac-4921-aca7-90a97509fa98 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate3d(-10.369437158468426%, 0, 0)","translate3d(0%, 0, 0)"]},"delay":0,"duration":5000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"both"}] [{"selector":"#anim-480da2ef-8ac2-43f8-ac4b-57776494b755","keyframes":{"opacity":[0,1]},"delay":0,"duration":600,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-a481a967-8745-43ef-9603-38869e22b4d3","keyframes":{"transform":["translate3d(0px, -530.09626%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":600,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] A few months before NCIS premiered in September 2003, CBS introduced the agency and its main characters via a backdoor pilot in another drama.

In a two-part season 8 episode of JAG — titled “Ice Queen” and “Meltdown” — Commander Harmon Rabb (David James Elliott) was a murder suspect in a case that NCIS was investigating.

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That’s when fans first met NCIS director Thomas Morrow (Alan Dale) and Special Agent in Charge Leroy Jethro Gibbs (Mark Harmon).

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As well as Dr. Donald “Ducky” Mallard (David McCallum), Anthony DiNozzo (Michael Weatherly), and Abby Sciutto (Pauley Perrette).

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Sean Murray (Timothy McGee) didn’t join the cast as a series regular until season 2. And Cote de Pablo’s Ziva David didn’t show up until season 3.

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