[2] Sondra was created when Bill Cosby wanted the show to express the accomplishment of successfully raising a child (e.g. a college graduate).
[4][5] Sondra is introduced partway through Season 1 as the eldest of Cliff and Clair's five children, a sophomore studying pre-law at Princeton University.
During Season 2, she meets and begins to date Elvin Tibideaux (Geoffrey Owens), a pre-med student and fellow Princeton sophomore.
Elvin irritates Cliff and Clair at first, but they eventually warm up to him and give their blessing to the couple's engagement near the end of Season 3.
By the start of Season 4, Sondra and Elvin are married and have completed their undergraduate studies, but shock Cliff and Clair with their plans to open a wilderness supply store rather than continue on to law and medical school.