The death of Diana Hyland during the production of the spring 1977 episodes forced major changes on the show. She had completed only four episodes as the mother of the family and was written out of the remainder as being "away." When the series returned with new episodes that fall, Tom Bradford had become a widower, his wife having died about "a year ago."
Even though Mark Hamill didn't like the more comedic direction in which the show was heading, he decided to honor his commitment to the show. However, the night the pilot aired, he was involved in a serious auto accident where he sustained serious facial injuries and was forced to quit the show. Hamill has stated numerous times that the full extent of his injuries was only a broken nose.
During the first couple of seasons, an instrumental version of the theme was played during the opening. However, in later seasons, lyrics were added and the theme was sung by Grant Goodeve, who played David.
Mark Hamill was in a one-car accident in January of 1977. He had severe facial injuries, and his scars were still visible two years later, while filming Star Wars: Episode V - The Empire Strikes Back (1980).
The kids, from oldest to youngest, were David, Mary, Joanie, Susan, Nancy, Elizabeth, Tommy, and Nicholas. In real-life, the actors and actresses rank thus: Joanie, Susan, Nancy, David, Mary, Elizabeth, Tommy, and Nicholas.
Lani O'Grady was the younger sister of Don Grady, who played Robbie Douglas on My Three Sons (1960), which was another popular family sitcom. Tragically, she died of a drug overdose on September 25, 2001. Don died of cancer on June 27, 2012.
Aside from Dick Van Patten, for the opening credits from seasons three through five, the main cast members, who did not appear in the pilot, were billed before those who appeared, mostly due to last name alphabetically. Betty Buckley, Grant Goodeve, Willie Aames and Dianne Kay, who did not appear in the pilot, are billed before Connie Needham, Lani O'Grady, Adam Rich, Susan Richardson, and Laurie Walters, who appeared in the pilot.