Mark Harmon Reflects on Casting Austin Stowell as Young Leroy Gibbs in NCIS: Origins: ‘That’s a Movie Star’ (Exclusive).Linh

Mark Harmon says there was “heavy competition” for the role he first created on ‘NCIS’ — until Austin Stowell walked into the audition room

Austin Stowell and Mark Harmon attend CBS' Fall Schedule Celebration at Paramount Studios on May 02, 2024 in Los Angeles, California. — Austin Stowell and Mark Harmon on May 2. Photo: Monica Schipper/Getty

Mark Harmon created one of network TV’s most beloved characters on NCIS back in 2003: Leroy Jethro Gibbs. How did he and fellow producers of new prequel series NCIS: Origins cast a younger version of the iconic special agent?

“I felt the room jump a little when Austin came in, before he said anything,” Harmon tells PEOPLE of Austin Stowell, the actor playing a 1991-era Gibbs in the new spin-off (premiering Monday, Oct. 14).

After his audition, recalls Harmon, “He walked out and someone said, ‘I’ll just say it, that’s a movie star.’”

The 73-year-old former Sexiest Man Alive is involved in Origins as well, as both executive producer and narrator — and appears in the premiere episode. It marks Harmon’s first reappearance as Gibbs since his departure from NCIS in 2021.

CIS: ORIGINS follows a young Leroy Jethro Gibbs (Austin Stowell) — Austin Stowell on ‘NCIS: Origins’.CBS

But the new drama is ultimately led by Stowell, 39, who admits to PEOPLE he’s “never been on a show like this.” It’s what made his casting so crucial.

“There was heavy competition there,” recalls Harmon of the other actors in contention for the role. “There were a lot of good people. I would say that there were really few who drew the attention Austin did.”

In fact, he adds, “I can say that about any role that was cast in this show, because they all came in one after another. We got everybody we wanted.”

NCIS: Origins follows the beginnings of Gibbs’ career as a special agent at the fledgling NCIS Camp Pendleton office, led by NCIS legend Mike Franks (Kyle Schmid, inheriting a role played in the flagship series by Muse Watson). Costarring are Diany Rodriguez as the no-nonsense Vera Strickland (played on NCIS by Roma Maffia), plus Mariel Molino, Tyla Abercrumbie, Bobby Moynihan and more.