David McCallum, known for his role as Dr. Donald "Ducky" Mallard on "NCIS," passed away on September 25, 2023. He had a successful career in television starting in the 1950s and appeared in shows such as "The Man from U.N.C.L.E.," "Colditz," and "Sapphire & Steel." His "NCIS" co-stars, including Lauren Holly and Michael Weatherly, paid tribute to him on social media. Fans and other actors, such as Katrina Law, also expressed their sadness at his passing. McCallum's death coincided with CBS' "NCIS Day," adding extra significance to his loss.