Mark Harmon Shares Amusing Admission About Gibbs’ Rules On NCIS

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David J. North, a co-creator of NCIS: Origins, playfully suggests Mark Harmon might surprise some viewers. Harmon recently returned as Leroy Jethro Gibbs for a special crossover episode between NCIS and NCIS: Origins. This marked Gibbs’ most significant appearance on the CBS series since leaving early in season 19.

Mark Harmon is returning to television through a new case. This case was originally investigated by a younger version of Gibbs (played by Austin Stowell) back in the early 1990s. Now, in season 23 of NCIS, Gibbs’ old colleagues are reopening the investigation – a death involving a naval officer. This will allow the show to revisit some of the principles that have guided Gibbs throughout his career, even though Harmon’s character doesn’t fully recall them all.

In a recent interview with Entertainment Weekly, co-creator Mark Harmon shared a story about recording voiceovers for the iconic rules of Leroy Jethro Gibbs, which have appeared throughout the NCIS series. Harmon, who starred in and produced most of the original NCIS and is also an executive producer on the prequel NCIS: Origins, admitted he doesn’t actually know all the rules – only maybe one of them.

We were recently recording voiceover work with Mark in the studio. I was explaining how episode 5 really centers around rule number 11 – ‘When the job’s over, walk away.’ Mark mentioned that fans constantly ask him about the rules. I was surprised and asked if he could even name one. He said, ‘I think there’s one about a knife.’

North also points out that the upcoming reveal could be upsetting for some fans, as Gibbs’ rules are so central to the show NCIS. While the exact number of rules isn’t always consistent—depending on who lists them—there are around 40. These rules cover things like keeping suspects separated, being precise when detecting dishonesty, and pushing boundaries instead of outright breaking them. North specifically highlights the rule about always carrying a knife.

CBS (via MoviesStillsDb)

Ducky Harmon made a notable return in a recent episode of the NCIS: Origins prequel, marking his first major on-screen role since leaving the original NCIS in 2021. He did have a brief appearance in the season one premiere of NCIS: Origins that same year. While he’s no longer a regular on NCIS, the actor hasn’t said he’ll never return to the main series.

Even though he hasn’t committed to returning full-time, there’s still a chance Gibbs might appear on screen again. The show hasn’t fully explained how the younger version of Gibbs transforms into the character fans are familiar with on NCIS, so Mark Harmon could potentially revisit the role and its many established rules.

NCIS: Origins season 2 airs Tuesdays at 9 p.m. ET on CBS.

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2025-11-16 16:18