…And in 1964 he had an idea. Playboy, Life and other magazines had their lavish color fold-outs, so Mad, he thought, should parody them with a cheap black-and-white fold-in.
From 2008: http://www.nytimes.com/2008/03/30/arts/design/30genz.html?pagewanted=all

Instead of conducting a formal interview, we invited Mr. Jaffee to explain the thought process behind his favorite Fold-Ins from over the years. He certainly didn’t disappoint. Read on to discover how one of the world’s finest optical satirists creates his magic on a monthly basis.
 From 2014: https://www.pastemagazine.com/books/state-of-the-art-mad-magazine-icon-al-jaffee-on-hi/

Al Jaffee, Iconic Mad Magazine Cartoonist, Retires at Age 99 … and Leaves Behind Advice About Living the Creative Life
From 2020: https://www.openculture.com/2020/06/al-jaffee-iconic-mad-magazine-cartoonist-retires-at-age-99.html

Al Jaffee, Now 102, Is Ready to Be Added to Mount Rushmore:
MAD’s longest-serving contributor on comedy, art, and the origins of the “Fold-in.”
From 2023: https://www.vulture.com/article/al-jaffee-interview.html

Al Jaffee on Artnet: https://www.artnet.com/artists/al-jaffee/

(updated 2023)