Brian Dietzen

NCIS' assistant medical examiner Jimmy Palmer can't stay lovably dim forever, right?

"I wanted the character to grow a little bit and learn a bit from what he's been doing the last seven years in autopsy," Brian Dietzen tells TVGuide.com of his character's growth this season. "Jimmy's always kind of been the bumbling guy who's a half a beat behind. We don't want to lose any of that, but ... if this guy hasn't learned a thing since the first season, he'd get canned pretty quickly."

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Jimmy will start on that path in Tuesday's episode, when a handful of interns are called into help with a kidnapping investigation. Unfortunately for Jimmy, he feels a little left out when his boss, Ducky (David McCallum), takes an interest in of one of the interns, Sarah Knox (guest star Elizabeth Wright Shapiro).

"Jimmy feels more than a little bit threatened by this gal coming into autopsy," Dietzen says. "It seems he can read the writing on the wall, and he tries to enlist the help of any of the other agents to give him a job and make him feel important. He fears that his importance in autopsy is slipping away. It's a really fun show for Jimmy because he's running around like a chicken with its head cut off.

"She knows a bit more than Jimmy does about Scotland, singing, and quite a few different things that Ducky really takes a shine to," Dietzen continues. "She's new, she's young, and she's eager to learn. That's all the stuff that Jimmy has been in the past, and he's sent into sort of a tailspin."

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Dietzen says his character's relationship with mentor Ducky is similar to his with McCallum in real life. "I get to go to work every day and work with a TV acting legend," Dietzen says. "We have some great guest stars on the show like Robert Wagner and Ralph Waite. ... It's great to meet these folks, but I never lose sight of the fact that I get to do it every day I go to work. There's a lot that's translated into the characters. Jimmy's always learning from Ducky, and I am constantly learning from David."

So will Jimmy be able to prove his value and get some affirmation by episode's end? "Absolutely not," Deitzen says with a laugh. "I think that would be great, but by the same token, it's smart of our writers to always keep the characters on their toes. It's great to have a conclusion where people say, 'You're loved and you're appreciated.' But sometimes they don't. I like it that certain things are left open-ended, and that's what they decide to do with this."

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Even so, Jimmy will appear in four of the next five episodes, which will give his character plenty of time to prove himself. "We're going to see a lot of Jimmy Palmer stuff," Dietzen says. "When I asked [executive producer] Gary Glasberg what I can say about this season, he said, 'Tell them they're going to get a lot more Jimmy goodness.'

"He's constantly learning," Dietzen continues. "There are going to be mistakes still made along the way. Although he's going to try to impress and try to do his job extremely well, Jimmy's always had a knack for asking questions about the obvious. As far as Jimmy becoming a very confident fellow who knows how to solve the case by himself, I don't think it will get to that point. But I do think the character will graduate to another level."

NCIS airs Tuesdays at 8/7c on CBS.