The “Gibbs’ Rules” Irony: He Doesn’t Know Them

For 20 years, fans have lived by “Gibbs’ Rules.” The long-standing rumor—confirmed by the NCIS: Origins showrunners in 2025—is that Mark Harmon can’t remember a single one of them. Whenever a fan asks him to recite a rule, Harmon reportedly smiles and says, “That’s for you to know, not me.” On set, he relied entirely on a “cheat sheet” hidden behind props or the script supervisor’s notes

He viewed the rules as a “gimmick” for the character, whereas the fans viewed them as a lifestyle. This disconnect is a running joke among the cast, with Sean Murray (McGee) reportedly knowing the rules better than Harmon himself.