Hirschfeld is known for hiding the name of his daughter, Nina, in all of the drawings he produced since her birth in 1945. The name would appear in a sleeve, in a hairdo, or somewhere in the background. Sometimes "NINA" would show up more than once, but Hirschfeld would helpfully add a number next to his signature, to let people know how many times her name would appear.
Hirschfeld collaborated with humorist S.J. Perelman on several projects, including Westward Ha! Or, Around the World in 80 Cliches, a satirical look at the duo's travels on assignment for Holiday magazine.
In 1991, the United States Postal Service commissioned Hirschfeld to draw a series of postage stamps commemorating famous American comedians. The collection included drawings of Stan Laurel, Oliver Hardy, Edgar Bergen (with Charlie McCarthy), Jack Benny, Fanny Brice, Bud Abbott and Lou Costello. He followed that up with a collection of silent film stars including Rudolph Valentino and Buster Keaton. The Postal Service allowed him to include Nina's name in his drawings, the only time a person's name has been hidden in a postage stamp in the United States.