By the 1920s, the Marx Brothers had become one of America's favorite theatrical acts, with their sharp and bizarre sense of humor. They satirized high society and human hypocrisy, and they became famous for their improvisational comedy in free-form scenarios. A famous early instance was when Harpo arranged to chase a fleeing chorus girl across the stage during the middle of a Groucho monologue to see if Groucho would be thrown off. However, to the audience's delight, Groucho merely reacted by commenting, "First time I ever saw a taxi hail a passenger". When Harpo chased the girl back in the other direction, Groucho calmly checked his watch and ad-libbed, "The 9:20's right on time. You can set your watch by the Lehigh Valley."