David McCallum, best known for his role as Dr. Donald "Ducky" Mallard on "NCIS," passed away on September 25, 2023. He had a long and impressive career in acting, with notable roles in "The Man from U.N.C.L.E." and "The Great Escape." Mark Harmon, who played Special Agent Gibbs on "NCIS," paid tribute to McCallum, expressing his admiration for the late actor. Harmon and McCallum had a strong bond, with Harmon even referring to McCallum's iconic character from "The Man from U.N.C.L.E." during their first meeting. Their mutual respect and friendship were evident on and off set.