From Wikipedia:
Mary Kay and Johnny is the first situation comedy broadcast on network television in the United States, was the first television program to show a couple sharing a bed, and was the first television series to show a woman's pregnancy on television.
Network runs
Mary Kay and Johnny debuted on the DuMont Television Network on Tuesday, November 18, 1947. The 15-minute-long weekly sitcom starred real-life married couple Mary Kay Stearns and Johnny Stearns. The Stearnses created and wrote all the scripts for the show. The program was broadcast live, most of the action taking place on a set representing the New York City apartment of the title characters, a young married couple. After a year on DuMont, the show moved to CBS for half a year, much of the time being broadcast every weeknight, and then ran for one more year each Saturday night on NBC, which broadcast the final episode on March 11, 1950.
In 1948, Mary Kay became pregnant in real-life. After unsuccessfully trying to hide it, the show's producers wrote her pregnancy into the show. On December 31, 1948, the Stearnses' son Christopher, less than one month old, appeared on the show and became a character.
Lost episodes
Before 1948, Mary Kay and Johnny was broadcast live and not recorded. In early 1948, still broadcast live, the show was also recorded on kinescopes so that it could be shown, with some delay, on the West Coast. The entire series from then until 1950 was recorded in this way. Many episodes survived in full as late as 1975.
The fate of the NBC episodes is unknown. Fragments of the show's last few episodes survive, most on 16-mm film; these are not commercially available, though TV Land used a clip in an episode of Inside TV Land called "Taboo TV".[citation needed]
The Paley Center for Media has one 1949 episode in its collection.