David Keith McCallum was a Scottish actor and musician. He gained wide recognition in the 1960s for playing secret agent Illya Kuryakin in the television series The Man from U.N.C.L.E. His other notable television roles include Simon Carter in Colditz (1972–1974) and Steel in Sapphire & Steel (1979–1982). Beginning in 2003, McCallum gained renewed international popularity for his role as NCIS medical examiner Dr. Donald "Ducky" Mallard in the American television series NCIS, which he played for 20 seasons until his death. On film, McCallum notably appeared in The Great Escape (1963), and as Judas Iscariot in The Greatest Story Ever Told (1965).

Illya Kuryakin is a fictional character from the 1960s TV spy series The Man from U.N.C.L.E. He is a secret agent with a range of weapons and explosives skills, and is described in the series as holding a master's degree from the Sorbonne and a Ph.D. in Quantum Mechanics from the University of Cambridge. Kuryakin speaks many languages, including French, Spanish, German, Arabic, Italian and Japanese. The series was remarkable for pairing an American character, Napoleon Solo, with the Russian Kuryakin as two spies who work together for an international espionage organization at the height of the Cold War.