Groucho's birth name was Julius Henry Marx. Named after his uncle Julius who was a performer, Groucho began performing vaudeville skits on stage at the age of 15 with the Leroy trio. Groucho's trademarks -- grease paint mustache, one-liners and double entrendres -- made him the most well known of the brothers with the general public.
In addition to his stage and movie career, Groucho had a successful radio and television career. He hosted "You Bet Your Life", which started on radio in 1947 and switched to television in 1961. Groucho was also the most outspoken and liberal of the brothers. He was investigated by the FBI because of his suspected communist sympathies.
Harpo's birth name was Adolph Marx. He changed his named to Arthur during World War I because he thought Adolph was too German. Harpo's trademarks included his curly hair and hats, his trench coat, his harp playing and, above all else, the fact that he didn't speak. Harpo did speak on stage but he never spoke in the movies. Harpo adopted the silent pantomime after a theater critic in Champaign, Illinois critiqued his vaudeville performance by saying his beautiful pantomime was ruined every time he spoke.
In addition to the Marx brothers movies, Harpo made several television appearances. The most well known appearance was on "I Love Lucy" in 1955 where Lucy mimicked Harpo's pantomime style. He published his autobiography, "Harpo Speaks," in 1961.
Chico was born Leonard Marx. He earned the nickname, allegedly, from his persistent pursuit of chicks. His reputation for amorous endeavors was a lifelong affair. Chico's trademarks included his thick dark curly hair, his doublespeak and his proficiency on the piano. Chico was regarded as the most charming and energetic of the brothers. He was also a gambling addict which led to a perpetual state of indebtedness.
Zeppo was born Herbert Marx and had a reputation as a street punk and troublemaker when he was younger. He was known as the straight man and romantic lead character in the Marx Brothers movies. He actually took over this role from his older brother Gummo. He felt overshadowed and always in the background of the other three. His character in the movies was primarily as a foil for Groucho and Chico. His last Marx Brothers movie was "Duck Soup" in 1933. He had a number of other careers including as a theatrical agent.
Gummo, born Milton Marx, is the least known of the Marx Brothers because he didn't appear in any of the movies. He was the first brother to appear on stage working with his uncle Julius. He performed with his brothers during the vaudeville stage of their career and was replaced by Zeppo when he joined the army. Gummo ran a successful talent agency and served as the Marx Brothers' manager for most of their career.