Cartoonist and comic strip artist Jack Mendelsohn grew up in Brooklyn. His father was Winsor McKay's film agent and one of Mendelsohn's idols was local cartoonist Stan MacGovern. A high school dropout and Navy enlistee, Mendelsohn began his career in comics as a freelance gag cartoonist for magazines like the Saturday Evening Post after World War II. He was a productive scriptwriter for funny animal, humor and fantasy comic books by Quality, Dell and DC, as well as the syndicated 'Felix the Cat' strip. Mendelsohn moved to Mexico in 1951 and spent most of the decade there. In 1959, he began his partially autobiographical comic 'Jacky's Diary', drawn in the style of a child. The strip ran from 1959 to 1961 and also had a comic book publication.
Upon the strip's cancelation, Mendelsohn moved in to television scriptwriting for Jay Ward's studio, as well as 'Scooby Doo' and the animated versions of 'Beetle Bailey' and 'Krazy Kat'. He was one of the writers of the Beatles' 'Yellow Submarine' in 1968 and during this period he also started writing for live-action television. He scripted for 'Rowan & Martin's Laugh-In' and was head writer of 'Three's Company' and 'The Carol Burnett Show'. In later years, he returned to animation as the story editor for 'The Teenage Mutant Ninja Turtles'.