NCIS star Mark Harmon initially felt compelled to reprise the role of Leroy Jethro Gibbs as the narrator of the NCIS prequel series NCIS: Origins because of his interest in exploring Gibbs’ history, especially in terms of introducing younger Gibbs as a probationary agent in the Naval Investigative Service office at Camp Pendleton in 1991, in the aftermath of the murders of his daughter and wife. However, Harmon was also drawn to NCIS: Origins by the chance to collaborate on the series with his son, Sean, who played the younger Gibbs in flashback scenes on NCIS over several seasons, and who now serves as an executive producer alongside his father on the prequel series, which is now set to enter its second season on CBS.
Indeed, the casting of Austin Stowell as Gibbs on NCIS: Origins was born out of Sean’s desire to focus on the creative direction of the prequel series along with the show’s strict adherence to continuity, as while Sean’s flashback scenes on NCIS are primarily set in the 1970s, NCIS: Origins presently encompasses events from 1991 and 1992. Moreover, this transition reflects justified confidence in Stowell, who has clearly distinguished himself in the role of Gibbs by infusing the younger incarnation of the character with his own distinctive personality and physical footprint.
Mark Harmon and His Oldest Son Brought the Younger Gibbs to Life on ‘NCIS’
In the first five seasons of NCIS, the role of a younger Leroy Jethro Gibbs is played in flashbacks by the now 73-year-old Mark Harmon. Harmon’s most notable flashback appearance came in the two-part third-season finale “Hiatus,” in which an explosion on a foreign ship puts Gibbs into a coma. While in a comatose state, Gibbs has flashbacks of being with his daughter Kelly and wife Shannon, who were both murdered in February 1991.
“Hiatus Part II” became the first NCIS episode to reveal that Kelly and Shannon were murdered by a Mexican drug dealer named Pedro Hernandez, who was then killed by Gibbs with a sniper rifle in Mexico, a crucial event that was revisited in the “Vivo o Muerto” episode of NCIS: Origins.
Sean Harmon first appeared as the younger Gibbs in the Season 4 episode “Heartland,” which shows the beginning of Gibbs’ relationship with Shannon, whom Gibbs married in 1982. Following “Heartland,” Sean appeared in five more episodes between the sixth and ninth seasons before making his final appearance as Gibbs in a Season 18 episode, “Everything Starts Somewhere,” which is most notable for showing the first meeting between Ducky and Gibbs.
However, while all of Sean’s flashback appearances on NCIS are memorable and touching to varying degrees, the most impressive collaboration between Sean and his father on NCIS is featured in the Season 9 episodes “Engaged (Part I)” and “Engaged (Part II),” which alternate between Gibbs’ present-day pursuit of a terrorist cell and his memories of undergoing Marine Combat Training at Camp Lejeune in 1972.
In the 1972 flashback scenes, Gibbs becomes infatuated with Private Joan Matteson, a young woman with whom Gibbs develops a growing bond, until Gibbs receives the shocking news that Joan was killed in a helicopter crash while headed to her first deployment in Okinawa.
The tragic event highlights the degree to which Gibbs’ career and life have been afflicted by fate. The haunting preoccupation that older Gibbs has with his fleeting memories of Joan in these episodes culminates in the emotionally overpowering final scene of “Part II,” which ends with Gibbs walking across a vast military cemetery before stopping and kneeling down to place flowers in front of Joan’s headstone.
Sean Harmon Developed the Concept For ‘NCIS: Origins’
For the now 37-year-old Sean Harmon, the experience of playing young Leroy Jethro Gibbs on NCIS led him to believe that an extended focus on Gibbs’ early years could form the basis for a successful series. Sean’s original concept for NCIS: Origins had the show beginning in 1991, with Gibbs struggling to come to terms with the trauma of losing his daughter and wife while trying to perform his investigative duties. After sharing this idea with his father, the elder Harmon suggested that the prospective series would benefit from having longtime NCIS writers David J. North and Gina Lucita Monreal as creators and show-runners.
Indeed, while the idea for NCIS: Origins was conceived by Sean, he’s only credited on the series as an executive producer, alongside his father. Moreover, while Sean is very much involved with the creative process, he has no intention of appearing as an actor in any future episodes. In a 2024 interview with TV Insider, Sean described his essential vision for NCIS: Origins. He said:
“I believe that very few people are actually ‘born leaders’ and are instead forged into them, and Gibbs is no exception. Digging into the back-story of ‘the boss’ seemed like a good opportunity to find out why Gibbs turned out the way he did and who was around to influence him on that journey.”
