Udo of Aachen

Udo of Aachen (1200–1270) is a fictional monk, a creation of British technical writer Ray Girvan, who introduced him in an April Fool's hoax article in 1999. According to the article, Udo was an illustrator and theologian who discovered the Mandelbrot set some 700 years before Benoît Mandelbrot.

Additional details of the hoax include the rediscovery of Udo's works by the also-fictional Bob Schipke, a Harvard mathematician, who supposedly saw a picture of the Mandelbrot set in an illumination for a 13th century carol. Girvan also attributed Udo as a mystic and poet whose poetry was set to music by Carl Orff with the haunting O Fortuna in Carmina Burana.