King Duncan, a character in William Shakespeare's play MacbethDuncan (fictional locomotive), a locomotive character in The Railway Series children's books by the Rev. W. AwdryDuncan, He-man's Man-At-Arms from the Masters of the Universe toyline, comics and cartoonDuncan Idaho, a fictional character in the Dune universe created by Frank HerbertDuncan Quagmire, a fictional character from A Series of Unfortunate EventsSer Duncan the Tall, a fictional character from Tales of Dunk and Egg, a series of novellas written by George R. R. Martin, set in the world of his Song of Ice and Fire cycle