The Truth About Mark Harmon's Behind-The-Scenes Feud On NCIS

"NCIS" has long been one of the most popular shows on TV, making Mark Harmon one of the most popular TV stars to boot. The Leroy Jethro Gibbs actor, better known just as Gibbs, has thrilled fans on the long-running CBS crime drama since 2003, but it sounds like fans could be seeing a little less of him as Gibbs' story continues on.

TV Line claimed in June that Harmon's big role on the series would be a little smaller for Season 19. It was suggested the actor would only be appearing in a small number of episodes, with a source saying he'd make just "a few" appearances. CBS didn't comment on the claims.

The report came after the dramatic Season 18 finale, "Rule 91," had fans pretty worried for Harmon's character when his boat blew up. Though it looked like it could have been 18 seasons and done for the star, Gibbs was later seen alive as he swam away from the explosion.

But while it sounds like things could potentially be winding down for Harmon, did you know the actor once had a pretty big feud on the "NCIS" set with someone integral to the show's success? Let's throw it back and take a deep dive into the drama.

Mark Harmon reportedly had drama with NCIS creator Don Bellisario

For this "NCIS" on set drama, we're heading all the way back to 2007 when it was revealed that Mark Harmon had some bad blood with a producer. According to TV Guide, Harmon had serious tension with showrunner and creator Donald "Don" Bellisario, which ended up with the latter stepping back from the crime drama.

Sources claimed Harmon was supposedly "frustrated" by Bellisario's "chaotic management style" and wasn't thrilled with the long hours he found himself working because of it. "Mark's been working every single day, 16 hours a day. [Bellisario] tries to micromanage everything. Script pages get faxed to the set at the last minute, and [Harmon] is tired of dealing with the huge impact that makes on his life," they purported.

And it sounds like things really got bad on the set all those years ago. An "NCIS" insider admitted, "The situation over at 'NCIS'? It's much worse than you think." Yikes. Bellisario went on to leave his showrunner role and focused on other CBS projects, but held on to his executive producer role.

David McCallum, who played Dr Donald "Ducky" Mallard, also dished on the drama to Digital Spy in 2014. "After a couple of years, we got to the point where we were getting scripts late from [Bellisario]. There was a little problem between Mark Harmon — who was representing the cast and crew — and Don, so CBS decided that Don would leave us."

What did Don Bellisario and Mark Harmon say about their feud?

It's safe to say Don Bellisario and Mark Harmon's drama played out in the public eye — so it was only a matter of time before one addressed what was really going on.

Bellisario opened up about his side of the story to Los Angeles Times in 2008, saying, "I asked Mark to re-shoot a scene. He redid it exactly the same way he did it the first time and never spoke to me again." Bellisario also accused Harmon of instigating a "full-blown PR campaign," as well as leaking information to the press. He added that he wished his time with the show had ended differently, claiming CBS asked him to develop other projects, seemingly as a result of the drama intensifying.

The super rich Harmon also had his say to the outlet, touching particularly on previous reports he was unhappy with the long days the cast and crew supposedly worked under Bellisario. "If we're working 14-hour days now instead of the 17- or 18-hour days that we were doing, it doesn't mean we're working any less hard. We're just more organized. This has become a very well-oiled machine," he said. Subtle shade? We think so!

Harmon cryptically added, "I don't wish to go head to head with Bellisario in the press... He knows why he left." Ooohhh...