Both men began separate careers as comedy and variety troupers in small-time burlesque and vaudeville before joining in 1910 to form the act of “Gallagher and Shean.” They went separate ways from 1914 to 1920, but in the latter year (at the urging of Shean's sister Minnie Marx, mother of the Marx Brothers) they rejoined to star in the Shubert Brothers' Cinderella on Broadway, with huge success. They then appeared in the Ziegfeld Follies of 1922, in which they sang their soon-to-be-famous song, “Absolutely, Mr. Gallagher? Positively, Mr. Shean!” (Shean wrote the music and Brian Foy the lyrics). Their popularity in this show and others was immense and inspired a host of imitators. Their success was short-lived, however. Gallagher became involved in a series of litigations—with Foy over song rights, with the Shuberts, with his third wife in a divorce suit, and with Shean. The team folded in 1925, and Gallagher suffered a nervous breakdown from which he never fully recovered; he died in a sanatorium four years later.

Shean continued in vaudeville and eventually moved into straight dramatic and comedic roles as a character actor on both stage and screen, appearing in 25 Hollywood films from 1934 to 1943.