Answer
Ray Harryhausen was mentored by Willis H. O'Brien, who is best known for his stop-motion animation in the films King Kong (1933) and The Lost World (1925). O'Brien taught Harryhausen the techniques of stop-motion animation, and Harryhausen went on to use these techniques in his own films, including The Beast from 20,000 Fathoms (1953), The 7th Voyage of Sinbad (1958), and Clash of the Titans (1981).