On November 21, 1980, Who Done It? (1980) was watched by 83 million people in the US and over 300 million worldwide. It was the highest rating for a single episode of a television series in American history until Goodbye, Farewell and Amen (1983) episode of M*A*S*H on February 28, 1983.
Originally, the show was intended as a starring vehicle for Victoria Principal, due to the fact that Pam would act as a buffer between the Ewings and the Barneses. J.R. was intended to be more of a supporting character. However, the producers were so impressed by Larry Hagman's portrayal of the immoral J.R., that he soon became the show's main character. Victoria stayed the hero though, and pretty soon it become angel Pam vs. Devil JR.
The house used as the "Southfork Ranch" house was a real Texas residence called "Duncan Acres", owned by Joe R. Duncan (or J.R. Duncan). When the show became popular, tourists from all over the world visited the house day and night. The Duncan family was forced to sell the house, and it is now a museum devoted to the show.
In several of the early episodes of the series, Lucy (Charlene Tilton) and Ray (Steve Kanaly) were often portrayed as lovers. However, when it was revealed that Ray was Jock's illegitimate son, and therefore Lucy's uncle, his affair with Lucy was never mentioned again.
When Steve Kanaly was talking about leaving the show due to his character's lack of development, it was Larry Hagman who came up with the idea to make Ray Krebs the illegitimate son of Jock Ewing in order to get Kanaly to stay.