Hitchcock was a six-time Academy Award-nominated English-American filmmaker who directed more than 50 feature films in a career spanning six decades. A master of the suspense thriller, he developed a style that is so distinctive that any filmmaker working in the suspense genre invariably risks comparison to him. He was one of the best known directors of his time, often making humorous cameo appearances in his own films. Hitchcock was also known for his use of MacGuffins, which are what? Discuss