HE PLAYS NCIS' handsomely bespectacled nerd Jimmy Palmer, who assists medical examiner Ducky (David McCallum). Dietzen came in to shoot a one-day guest appearance near the end of the first season — and has been on most of the episodes since, thanks to "his comic timing and the way he plays so well with McCallum," says exec producer Shane Brennan.
WHY WE LOVE HIM Because he's an increasingly competent but still socially awkward naïf. "Gibbs [Mark Harmon] is kind of a Superman with his superhero team. You've got one guy who's an average dude," says Dietzen.
PALMER...JAMES PALMER Jimmy's biggest weakness? A penchant for James Bond—like one-liners about the deceased. "Everyone looks at him like 'Really?'" says Dietzen. "And Jimmy's going, 'You're right — sorry, guys. Won't happen again.'" Happily, it will.