David McCallum, known for his roles as Dr. Donald "Ducky" Mallard in NCIS and Illya Kuryakin in The Man from U.N.C.L.E, has passed away at the age of 90. NCIS executives Steven D. Binder and David North praised McCallum as a scholar, gentleman, and consummate professional. McCallum's early life was in music, but he later shifted his focus to acting. He made a significant impact in the United States with his role in The Man from U.N.C.L.E and went on to feature in notable films. He is survived by his wife and children, and an "In memoriam" card will be shown during an NCIS marathon on CBS.