Mark Harmon has left NCIS after 18 full seasons, but he almost quit the show back in 2007 during season 4. Throughout the series' impressive run on CBS, various stars have come and gone, like Michael Weatherly and Cote de Pablo, but Harmon has been the glue holding the team together, both on and off the screen. He's also been an executive producer on NCIS since the show started in 2003.
His departure during season 19 has raised questions of whether NCIScan survive without Harmon's Gibbs, but
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