Actor David McCallum, famous for his roles in "The Man From U.N.C.L.E." and "NCIS," passed away at the age of 90, leaving fans saddened. Although his co-star Mark Harmon received a proper farewell on "NCIS," McCallum's character, Dr. Donald "Ducky" Mallard, had a diminishing presence on the show in recent seasons. McCallum's final appearance as Ducky was in the Season 20 finale. Despite his smaller role, McCallum's legacy as a prolific TV star of his generation remains, with his 20-year run on "NCIS" beloved by fans.