["Happy Days"] is a sitcom about the ostensibly innocent fifties. The decade itself is presumed to be a sitcom….

Richie, Potsie and Fonzie are fixated on ponytails. They spend one half-hour wondering how "to go all the way" with a ponytail. They spend another half-hour wondering whether, if they had a car, they would automatically get a ponytail. They spend a third half-hour getting drunk with some Marines, in order to make themselves more worthy of ponytails….

If all this strikes you as "Ozzie and Harriet" with hair on their palms, you're right. Come back, Ricky Nelson, all is forgiven. Amazing: So many people behaved the way they did in the fifties because the sitcoms of that decade told them that was how they were supposed to behave. Now, in the seventies, we have a sitcom based on those sitcoms, a marvel of imaginative recycling. The producers call...