Wisconsin, That '70s Show depicts the life of teenager Eric Forman (Topher Grace) and his five teenage friends: Donna Pinciotti (Laura Prepon), his liberal girlfriend and next-door neighbor, Steven Hyde (Danny Masterson), a rebellious hard-rocking stoner who was adopted by the Forman family and lives in their basement, Michael Kelso (Ashton Kutcher), a dim-witted narcissistic ladies man, Jacqueline Burkhart (Mila Kunis), a self-involved high school cheerleader overly preoccupied with wealth and status, and Fez (Wilmer Valderrama), the nicknamed immigrant from an ambiguous country of origin and whose hormones are raging out of control. The latter character's name is known to have originated as a loose acronym for Foreign Exchange Student.
Relationships among the teens are explored, the primary focus being between Eric and Donna, who are the responsible ones, as evidenced in episodes such as "Dine and Dash". Their relationship sharply contrasts with the on-again, off-again relationship between Kelso and Jackie, who were usually portrayed as mutually obsessed despite their arguments and denials of love to spite one another. In both relationships, the couples would have harsh disagreements, but would come to terms with their differences. Jackie eventually moved on to Hyde and later Fez as the series progessed.
Other main characters include Red Forman (Kurtwood Smith), Eric's overbearing war veteran father, Eric's overprotective menopausal mother Kitty (Debra Jo Rupp), who is struggling to be a fulltime mom and housewife while maintaining a job as a nurse in a local hospital, and Laurie Forman (Lisa Robin Kelly, 1998-2003 and Christina Moore, 2003-2004), Eric's older sister, whose promiscuity is the brunt of many jokes by the teenagers but does not deter Kelso from making moves on her. The show also depicts the relationship of Midge and Bob Pinciotti (Tanya Roberts and Don Stark), Donna's dimwitted parents, both of whom are easily influenced by the 1970s movements and fads, which places occasional stress on their marriage. Tommy Chong appeared as a frequently recurring character, Leo, the aging hippie owner of the Foto Hut.
 Eighth season changes
Eric Forman and Michael Kelso were written out of the series after the seventh season, as actors Topher Grace and Ashton Kutcher were to star in movies to be filmed during that season (Grace in Spider-Man 3 and Kutcher in The Guardian). Longtime characters such as Leo returned with more prominent roles to help fill the gap. A new character named Randy Pearson, played by Josh Meyers, was introduced to take Eric Forman's place. Another new character, Sam, played by Judy Tylor, was added to the cast as Hyde's wife.
Kelso appears in the first four episodes of the eighth season (with Kutcher credited as a special guest star) before moving to Chicago; both he and Eric returned for the series final episode. The location of the show's introduction was also changed from Eric's Vista Cruiser to the "Circle".