'NCIS' Star Mark Harmon Credits This for Show's Longterm Success

Mark Harmon knows NCIS wouldn't be as hugely successful as it is without its dedicated fanbase. The NCIS star and executive producer told Parade last month that although it took the series a while to find its groove, the fans are responsible for keeping it there.

"We didn't find [our groove] until year seven or six," Harmon said. "And we've been there ever since. That's because of the fans."

He offered up "a big thank-you" to the fans, adding, "I don't ever take it for granted."

With NCIS entering its 17th season, Harmon's Leroy Jethro Gibbs is one of the only characters in the entire show to appear in all of the seasons to date — and the upcoming season could even bring back an old friend.

During the Season 16 finale, fans were shocked to see the presumably dead Ziva (Cote de Pablo), who stepped into Gibbs' basement to warn him of danger coming his way.

"Hello Gibbs. No time for pleasantries. You're in danger," she told her old friend in the scene. "Well, aren't you going to say something?"

Gibbs was too shell-shocked to say anything, simply uttering Ziva's name as the episode reached its dramatic cliffhanger-heavy conclusion.

Some fans thought the return of Ziva was too good to be true. "I THINK IT WAS ALL A DREAM BY GIBBS, BUT WE SHALL SEE!" one fan wrote on Facebook.

"Over hype we will most likely be disappointed it may all be a dream and I hope not," another user theorized.

Others wondered if Gibbs' history of being haunted by ghosts of his past could point to Ziva being a mere hallucination. Elsewhere in the finale episode, he was haunted by the ghost of his ex-wife as he helped to care for her daughter.

But the first trailer for the Season 17 premiere showed that Ziva is most definitely alive and well, showing the aftermath of the basement reunion, which is rudely interrupted by gunfire and an explosion.

Season 17 will see de Pablo reprise her role of Ziva in four episodes, as the mysteries surrounding her return and the enemies coming after her and Gibbs unfold.

What will Ziva's return mean for the beginning of the season? NCIS returns for Season 17 on Tuesday, Sept. 24 at 8 p.m. ET on CBS.