In 1950s Milwaukee the Cunningham family must contend with Fonzie, a motorcycle riding Casanova.
Potsie sets Richie up with a girl known to have a reputation. Richie doesn't get far with her but leads Fonzie and others to believe he did.
Tired of driving around in Howard's DeSoto, Richie and Potsie buy a car of their own. The car has several problems including an engine that won't run consistently. This causes problems when they try to impress two girls.
Richie and Potsie are invited to Potsie's cousin's stag party. In an attempt to lessen the effects of the alcohol they will consume, they each drink several cartons of milk and a sip of olive oil.
Potsie is staying with the Cunninghams, and he and Richie sneak out to watch a drag race in which Fonzie is involved.
Richie buys tickets to a rock and roll show from Fonzie but has to work at the hardware store when Howard needs to have his tonsils removed. Because he'll be working until 9:00 PM, he won't be able to go to the show, so he asks Fonzie for a refund. Later, Howard tells Richie that he can close the store at 5:00 PM leaving him free to go to the show. He, now, has to ask Fonzie for the tickets back.
Richie and Potsie, in their never-ending effort to get girls, decide that they want to join a gang called the Demons. However, in order to be accepted, they have to perform several dares.
After taking a look at a B+ Potsie got on an exam, Fonzie decides to drop back into school. He asks Richie to do his homework and cheat for him.
Richie and Potsie obtain fake identification cards in order to attend a burlesque show where Ralph says Bubbles McCall takes it all off.
Richie and his girlfriend, Arlene, break up after two weeks of dating. Neither of them have dates for the prom, so they end up going together as friends.
To make some money, Richie, Potsie, Ralph, and Bag form a band. They secure a gig, but Richie and Potsie lose the money (including that of Ralph and Bag) playing poker.
Richie is put in an awkward situation when he is set up with a girl much taller than he is. Meanwhile, Howard is frustrated by Marion's ineptness at playing bridge.
Cindy, a new girl in school, asks Richie to tutor her. Richie is interested in more than just studying and makes several attempts to win her over.
Richie meets a beatnik named Diedre at the movies and gets caught up in her type of lifestyle.
Howard's old army buddy, a black man, asks Howard to be the best man at his wedding. Howard and Marion consider holding the wedding at their home when the man can't find anyone else willing to do it.
Richie gets on the good side of a local gang, the Dukes, when he protects the leader's sister from being picked on. However, things change when the Dukes steal Potsie's bike, and Richie tries to get it back.
Howard wants to buy a bomb shelter to protect his family. Problems quickly arise when several of Richie's friends ask if they can use it.
