The producer of I Love Lucy helped to create the multiple-camera setup still used in most sitcoms today.
Countless sitcoms today use the multiple camera, adjoining set setup that was first made by Desi Arnaz, producer of I Love Lucy. While popular comedies like The Office, Modern Family, and Community don't use this setup, others like How I Met Your Mother, Two and a Half Men, and The Big Bang Theory still do. Arnaz and his cameraman Karl Freund are credited with the development of that setup still used today, as well as the production style associated with it in which all the sets are adjacent to one another. This helped to enable every station around the country to broadcast high quality images of I Love Lucy. Arnaz is also credited with inventing the live studio audience setup. Though he was told it would be impossible to allow an audience onto a sound stage, he worked with Freund to design a set that could allow for an audience and filming, while adhering to fire and safety codes. Arnaz also pushed the envelope for making the network let him show Lucille Ball while she was pregnant. Back then the CBS network felt pregnant women should not be on television, but the priest, rabbi, and minister Arnaz consulted all said it was fine. (Source)