Part of Mostel's duty with the Public Works of Art Project (PWAP) was to give gallery talks at New York's museums.
Leading groups of students through the many paintings, Mostel could not suppress his comedic nature, and his lectures were noted less for their artistic content than for his sense of humor.
As his reputation grew, he was invited to entertain at parties and other social occasions, earning three to five dollars per performance.
Labor union social clubs followed, where Mostel mixed his comic routine with social commentary.
These performances played a large role in his eventual blacklisting in the next decade.

In 1941, the Café Society, a downtown Manhattan nightclub, approached Mostel with an offer to become a professional comedian and play a regular spot.
Mostel accepted, and in the next few months he became the Café Society's main attraction.
It was here that he adopted the stage name Zero (Zee to his friends), created by press agent Ivan Black at the behest of Barney Josephson, the proprietor, who felt that "Sam Mostel" was not appropriate for a comic.

Thus, at the age of 27, Mostel dropped every other job and occupation to start his show business career.
Part of Mostel's duty with the Public Works of Art Project (PWAP) was to give gallery talks at New York's museums. Leading groups of students through the many paintings, Mostel could not suppress his comedic nature, and his lectures were noted less for their artistic content than for his sense of humor. As his reputation grew, he was invited to entertain at parties and other social occasions, earning three to five dollars per performance. Labor union social clubs followed, where Mostel mixed his comic routine with social commentary. These performances played a large role in his eventual blacklisting in the next decade.
In 1941, the Café Society, a downtown Manhattan nightclub, approached Mostel with an offer to become a professional comedian and play a regular spot. Mostel accepted, and in the next few months he became the Café Society's main attraction. It was here that he adopted the stage name Zero (Zee to his friends), created by press agent Ivan Black at the behest of Barney Josephson, the proprietor, who felt that "Sam Mostel" was not appropriate for a comic. 
Thus, at the age of 27, Mostel dropped every other job and occupation to start his show business career.
Zero Mostel