In 1956 Mingo answered a New York Times ad for an illustrator, and was selected by Mad publisher William M. Gaines and editor Al Feldstein to create a warmer, more polished version of a public domain character the magazine had been using. Previously, the magazine had printed a rougher image and redrawings of the character, which were randomly dubbed "Melvin F. Coznowski" or "Mel Haney" in addition to "Alfred E. Neuman." The pollyannic simpleton had appeared in many guises and variations since the 19th century, including in dental advertisements that assured the public of minimal tooth-pulling pain. Permanently named Alfred E. Neuman, the character became Mad magazine's mascot with issue #30. In November 2008, Mingo's original cover featuring the first "official" portrait of Neuman sold at auction for $203,150.
Norman Mingo crafted several Mad covers in 1956-7 before leaving the magazine. He returned to Mad in 1962 and painted most of its front covers until 1976. His last Mad cover appeared on issue #211 (December 1979). Combining the regular issues (including some back covers), the reprint "MAD Specials" and the paperbacks, Mingo did more than 200 original covers for Mad. Fellow cover artists Jack Rickard and Bob Jones have remarked that Mingo was the only one who could paint the Neuman character perfectly 'on model' every time.
A born again Christian, Mingo began signing his covers (executed in gouache) with the ichthys beneath his name in 1975, beginning with Mad #174.
Although Mingo has been named as the artist who created the definitive Neuman face, he created a dramatic variation in 1979—after the nuclear accident at Three Mile Island. With an exaggerated version of the meltdown in the background, on the cooling towers, Alfred abandons his trademark grin and says, "Yes...me worry!"
Semi-retired when he took his first Mad magazine cover assignment, Norman Mingo was the only veteran of the First World War ever to write or draw for Mad.
An obituary for Mingo appeared in the May 9, 1980 issue of the New York Times.