Karen centers on the social life of 16-year old Karen Scott, a typical mid-1960s American teenager who lives in a fashionable apartment complex at 90 Bristol Court in Los Angeles, California, with her tomboyish younger sister Mimi and parents Steve and Barbara.

Karen's friends include Janis, Candy, Peter, Spider Gibson, and David Rowe III.

After the last episodes of Harris Against the World and Tom, Dick and Mary aired on January 4, 1965, 90 Bristol Court ceased to be a programming entity, and handyman Murdoch disappeared from Karen as well.

"[4][5] The show premiered on NBC as 90 Bristol Court: Karen on October 5, 1964, and continued under that title through the broadcast of January 4, 1965.

In mid-November 1964 The New York Times reported that NBC planned to cancel both and Harris Against the World and Tom, Dick and Mary, effective in early January 1965.