'Everybody Sing', the 1938 MGM musical that featured Judy Garland, Allan Jones, Fanny Brice, and Billie Burke. In the musical number billed as "Snooks (Why? Because!)" , Brice played the character she became known for, Baby Snooks, a precocious little girl. She is joined in the number by Judy Garland, still a teenager herself. The song was written by Harry Ruby and Bert Kalmar, a pair of Jewish American writers who started in vaudeville, The duo had written the score to many movies, including some of the greatest of the Marx Brothers, like 'Animal Crackers', 'Horse Feathers' and 'Duck Soup'. The film is all about a family full of eccentricities, from the young teen girl to the parents to the housekeeper. Garland plays the young girl struggling to find a place to fit in, while Brice plays the Russian maid. As if often the case in the musicals of the 1930s and 1940s, the family and those around them decide to put on a show. One of those numbers is "Snooks (Why? Because!)", sung by Brice and Garland.
You can purchase 'Everybody Sing' on DVD from many online stores, including Amazon.