NCIS legend Mark Harmon's return as Gibbs confirmed after three years off-screen

NCIS legend Mark Harmon is officially returning to the small screen in CBS's highly-anticipated spin-off, NCIS: Origins. Fans will be treated to a surprise appearance from Leroy Jethro Gibbs in the very first episode.

The prequel delves into Gibbs' early years, when the agency was still known as the NIS, with rising star Austin Stowell taking on the role. Although already on board as narrator, co-showrunner David J North sent fans into a frenzy, confirming a cameo appearance from Harmon.

"That was a discussion between Mark, myself and [co-showrunner] Gina Monreal," David explained during a recent NCIS panel, per TVLine. "I hope the audience will be excited to see him after so many years."

Details surrounding Gibbs' reappearance are being kept under wraps and are sure to have fans on the edge of their seats until the show's premiere next month, reports the Express .

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Could we be about to get an update on Gibbs' life after leaving the team in 2021?

Or will the prequel treat us to a flashback, revealing a behind-the-scenes moment from a past mission?

But that might not be all, with David hinting at further appearances for Harmon down the line. It seems Gibbs' story is far from over.

"We are focusing on him telling the story of 1991," he said. "As far as Mark appearing again, we are open to anything."

Millions are expected to tune in when Origins premieres on the same day as the upcoming 22nd season of the main NCIS show.

A trailer was recently released amidst controversy after the spin-off was announced following the cancellation of NCIS: Hawaii.

However, some fans admitted the series looked "better than they thought" after seeing the first footage.

"This looks way better than I thought it would and it has that streaming service quality to it," one fan commented on YouTube.

Another admitted: "I thought this was gonna be terrible. But this looks amazing."

However, many more will be waiting to pass judgement until the series has actually aired in just under a month's time.

NCIS: Origins premieres Monday, October 14 on CBS. NCIS is available to stream on Disney+.