Desi Arnaz invented the rerun during the pregnancy episodes of the series by re-playing some episodes (and changing some of the scenery and lines) from the first season to give Lucille Ball time to rest and care for their newborn son Desi Arnaz Jr.
Lucille Ball decided to go ahead with the series after having a dream in which Carole Lombard - the screwball comedy actress that died in a plane crash and who was a close friend of Lucy - recommended she take a shot at the risky idea of entering television, and to get off of radio.
William Frawley, aka "Fred Mertz," had a well known and longtime issue with alcoholism. He was advised in the beginning of the series to stay sober, or be terminated. So, if you look closely, a majority of his scenes display his character having his hands deep in his pockets. This would therefore not show his hands trembling, due to alcohol withdrawals.
This was one of the first TV shows to be filmed in Hollywood, at a time when many shows were done live in New York. It pioneered the use of three film cameras simultaneously, and the results were high-quality prints of a classic comedy series preserved for future TV audiences.
CBS executives balked heavily at the casting of William Frawley, owing to his reputation as an alcoholic and general rabblerouser. After his hiring, Desi Arnaz informed him that if he came to work drunk or missed work for anything besides a genuine illness more than one time, he'd be written out of the show.
Frawley never arrived at filming drunk or impaired, and typically learned his lines quicker than the other series regulars. He and Arnaz became and remained close friends, even years after the show ended production.
Frawley never arrived at filming drunk or impaired, and typically learned his lines quicker than the other series regulars. He and Arnaz became and remained close friends, even years after the show ended production.