Ivan Reitman, who as producer, director or both was a force behind some of the most successful and beloved film comedies of the last 45 years, including “National Lampoon’s Animal House,” “Stripes,” “Ghostbusters,” and “Twins, died on Feb. 12 at his home in Montecito, CA. He was 75.

Mr. Reitman made his mark with movies that often featured memorably outrageous scenes and unexpected casting. Critics sometimes complained that his films could seem too loosely structured and acted, something often attributed to his casting of comedy improv actors. But those who worked with him said there was method behind the onscreen madness he orchestrated.