The main teenage cast members were Topher Grace, Mila Kunis, Ashton Kutcher, Danny Masterson, Laura Prepon and Wilmer Valderrama. The main adult cast members were Debra Jo Rupp, Kurtwood Smith, Don Stark, Tommy Chong and Tanya Roberts.

The creators had wanted the show to have a 1970s "feel" from the beginning, so opted to set the series later in the decade, when trends and political ideologies had become firmly established and disseminated. The idea that the duration of the series would carry sociopolitical undertones also necessitated a chain of social events which could influence the characters. Thus, 1976 was chosen, which allowed episodes set within a short time frame to address streaking, the sexual revolution, the Equal Rights Amendment, the 1973 oil crisis, and the presidencies of Richard Nixon and Gerald Ford, all of which were culturally influential events that occurred in the earlier years of the 1970s. The shift to 1977 during the last half of the first season also allowed the inclusion of the first Star Wars movie, which premiered in May 1977.