David J. North: “It's not like any piece of wardrobe. It's definitely cherished, but they shoot the original NCIS up in Valencia, California, and we reached out to them and asked for the hat, and that's how that's how we had it. But yeah, it was a really cool thing and Adam was so excited.”

"NCIS: Origins" honors David McCallum in a tribute episode Oct. 28 featuring young "Ducky" Mallard's return. USA TODAY gets an exclusive sneak peek.

“He always had a way of knowing who I was meant to be.” So says Mark Harmon in the emotional voiceover that caps off the NCIS: Origins serving as a tribute to the late David McCallum, with Adam Campbell reprising his role as the young Ducky.

But arguably the biggest reveal came with learning why Ducky talks to bodies, which we saw the late David McCallum did when he was playing him for so many years on NCIS. Origins co-showrunner Gina Lucita Monreal and Campbell opened up to CinemaBlend about telling this “difficult” story and more.

Dietzen has since taken to Instagram to share a memory of his late co-star as well as an unusual gift from a fan. The 47-year-old revealed that he was moving and found a present of a McCallum action figure from when he starred in the 1960s action series The Man From UNCLE.

This will be Stowell’s first episode working with Campbell; the actor played young Ducky in four NCIS episodes, and on the mothership, young Gibbs was played by Sean Harmon (who is an exec producer on Origins ). “Ducky is undeniably charming, able to win over the grumpiest of grumps,” notes Stowell.