Mo Leff has worked as an artist on the syndicated boxing strips 'Curly Kayoe' and 'Joe Palooka'. He worked as Al Capp's assistant on 'Li'l Abner' in the 1930s, until he went to work for Ham Fisher to ghost on 'Joe Palooka' in the late 1930s. It wasn't until Fischer's death in 1955, when Leff started signing the strip. Leff worked on 'Joe Palooka' until 1959, when Tony di Preta took over.
Also in the 1930s, he worked with his brother Sam on Vic Forsythe's 'Joe Jinks' strip for United Features. They took over the comic officially in 1944, and renamed it to 'Curly Kayoe'. In 1946, Mo Leff retired from the strip, and it was continued by Sam alone. In addition, Mo had done his own 'Peter Pat' Sunday page for United Features from 1934 to 1938. He also contributed to the syndicate's comic books, like Tip Top Comics. Leff presumably also drew for Harvey Comics' comic book titles featuring 'Joe Palooka' supporting characters 'Humphrey' and 'Little Max'.
