Isao Takahata
"Le Roi et l'oiseau" ("The King and the Mockingbird"), 1980, directed by Paul Grimault. Begun in 1948 as "The Sheperdess and the Chimney Sweep"; cited by the Japanese directors Hayao Miyazaki and Isao Takahata as an influence. Originally produced in 1948, it had a production time of over 30 years, making it one of the longest production periods in history.