Mischief-maker Urkel and his troublesome transformation chamber move in with the Winslows and he wreaks household havoc by shrinking both himself and Carl in an experiment gone awry.

Steve and Laura have an accidental encounter in their birthday suits; Hariette unwraps an expensive gift she thinks Carl bought her for her anniversary. While they both get ready to take a shower, Steve and Laura accidentally see each other naked in the bathroom-a traumatic experience for both of them. Meanwhile, Carl's neighbor, Larry Johnson, asks Carl to hold onto an expensive diamond bracelet because Larry's wife is a snoop. But when Harriette finds it, she thinks Carl bought it for her anniversary gift, and he has some explaining to do.

Steve has a secret crush on Agnes fellow bug collector. Steve meets a gorgeous bug collector, Agnes Pritzker, on the Internet and invites her over to trade insect specimens. Steve fantasizes about kissing her and feels so guilty that he confides in Laura. Laura tells him to confess to his girlfriend, Myra, if it bothers him so much. Steve worries about Myra's reaction, but when he tells her about his thoughts of cheating on her, she says it's okay to fantasize, just not to act on it. Meanwhile, Harriette insists that Carl allow her boss, Nick Neidermeyer (Orbach), to play poker with him and his buddies in their weekly game. Nick wins repeatedly, makes obnoxious jokes and acts rudely. But Carl and the others endure it so Harriette doesn't get in trouble at work. Finally, at the next game, Harriette confronts Nick about his behavior and finds out that he will be transferred to a lower division and has no power over her anymore. Carl and Harriette throw Nick out of the house.

An English class full of unruly hooligans gives substitute teacher Urkel a pain - along with a creative scheme to get through to his defiant charges. Steve's English teacher, Mr. Donald Ludke, needs to take two days off so he appoints Steve as the substitute teacher. The first day, everyone but Laura and Myra ignores Steve, and two bullies, Kissel and Robbins, play tricks on him. But the second day, Steve uses his transformation machine to become Stefan Urquelle, who humiliates Kissel and takes charge of the class. Then Stefan teaches Robbins a love poem that helps Robbins get a date. Meanwhile, Harriette berates Carl for not helping with the housework. He hires a sexy maid, Tawny, further angering Harriette. The next day, she terminates Tawny and hires a muscular male servant, Geoffrey, to teach Carl a lesson. Carl agrees to help Harriette more often.

Eddie and his new girlfriend, Greta, dance until late at night to the music of pop stars Ziggy Marley and the Melody Makers (themselves) in the Winslows' living room. When Greta returns home past her curfew, her father forbids her to go out with Eddie for a month. Eddie convinces Steve to go to Greta's house and pretend to be her new boyfriend. Once her father lets her go out with Steve, Eddie takes her away for a date. But Eddie gets a flat tire and brings Greta home late again-and this time Steve gets the blame. Meanwhile, Mother Winslow gets called for an audit by the Internal Revenue Service. When Carl accompanies her, she accidentally gets him in trouble too.

Jaleel White has a dual role as Myrtle, Urkel's visiting cousin from Biloxi - who shows plenty of moxie when she squares off with Greta for Eddie's affections. The Winslows breathe a sigh of relief when Steve goes away to visit his parents in Russia. Unfortunately, Steve's Southern belle cousin, Myrtle Urkel, appears to pursue her true love - Eddie.

When Laura's emotions go into overdrive for drag racer Curtis, Urkel soups up the Isetta and challenges the daredevil to a race. In an effort to distract Laura from Curtis Williams, a flirtatious high school senior, Steve challenges him to a car race. Steve converts his wimpy little car into a powerful racing machine. Meanwhile, Eddie has annoyed Carl ever since he moved back home. After Eddie's friends keep coming over and making noise, Carl tells Eddie to respect the others in the house.

Laura and Myra's friendship turns stormy as they compete for the same sales job at Ferguson's; a rainstorm renders Urkel a ""human lightning rod"" and he refuses to go outside after being struck by lightning three times. Luckily, he finds out the cause: His ""boss sauce"" that he uses in his transformation machine contains a huge amount of iron. Meanwhile, Laura and Myra compete for the same sales job at a department store.

Steve is put in charge of building the school's homecoming parade float. With some difficulty, he gets volunteers to build a beautiful float. Unfortunately, while transporting it to the school, Steve crashes the float and destroys it. Although the volunteers are upset, they realize that the happy memories and friendships developed while building the float will last forever. Meanwhile, Mother Winslow sustains a series of minor injuries in her strenuous hobbies, including karate and square dancing. Carl worries that she should slow down in her old age before she really hurts herself.

Carl's bah-humbug attitude toward Urkel's rooftop Christmas decorations changes once he learns that winning a decorating contest could bring the Winslows a sackful of holiday cheer. Meanwhile, Harriette is saddened because Laura and Eddie seem to be too busy to participate in family Christmas activities.

Carl backpedals on his refusal to teach Urkel to ride a bike when it seems that the clumsy kid might wreck his new car. Laura brushes off Maxine's wish to become a hairdresser as foolhardy. Steve really wants to go on a class bicycle trip with Myra, but he doesn't know how to ride a bicycle. When Carl refuses to teach Steve how to ride a bicycle, Steve tries to teach himself. The clumsy Steve almost kills himself until Carl finally feels sorry for him and helps out. Meanwhile, Laura and her best friend, Maxine quarrel over whether Max should go to college or cosmetology school. Also, Carl becomes enamored with his new car.

Waldo visits the tiny island nation of Porto Santo and accidentally gets arrested for theft. When Carl, Steve and Eddie find out, they fly there and try to get him released. The police chief, Jaime Gutierrez Garcia , who is also the mayor and the governor, offers to release Waldo if Carl pays a huge fine. Carl doesn't have enough money, so he, Eddie and Steve secretly help Waldo escape that night. But Garcia catches them and threatens to jail all four. Luckily, he also explains that Porto Santo dollars are worth a lot less than American dollars and the fine is actually pretty small. Waldo, Carl, Eddie and Steve return home. Meanwhile, Laura is reluctant to go on a date with a boy she has never met whom Harriette recommends. She would rather date the polite pizza delivery boy, David Phillips, who comes to the house on the night of the date. Then Laura finds out that David is the one her mother likes. Harriette wanted Laura to decide for herself whether she likes David, which Laura appre

Handyman chores leave Urkel hyped up and hammered out after he inadvertently downs Laura's diet pills, which she' s using for a quick trim down.

Teamwork and the transformation chamber give Carl and Urkel an advantage in fighting off gang members looking to ransack the police warehouse. After Steve causes havoc with yet another of his inventions, Carl forces him to bring all of his scientific equipment to a police warehouse that night. While they're there, three hoodlums break in, tie Carl and Steve up and start robbing the place. Steve convinces them to let him demonstrate his transformation machine before they steal it, and he transforms Carl and himself into karate experts. A huge fight ensues, and Carl and Steve defeat the criminals. Carl gratefully allows Steve to move his equipment back to the house. Meanwhile, knowing that Harriette will object, Laura gets a nose ring without telling her. Harriette furiously tells her it's not the ring she minds but the fact that Laura did not ask permission. Laura reveals that it's a fake ring and says that she is now asking permission for a real one since it's okay with Harriette. Harr

Carl issues an ultimatum concerning Eddie's recent drinking habits; meanwhile at the local cafe, female fans become intoxicated by the jazz styling of the ultra cool Stefan Urquette. Eddie, now a member of a fraternity at college but living at home, starts drinking alcohol excessively. Carl demands that if Eddie comes home drunk again, he must move out. After the next incident, Carl tells Eddie to move in with Waldo. But Waldo surprisingly refuses, saying that Eddie becomes obnoxious when he is drunk. Eddie realizes that his father is right; he shouldn't drink alcohol until he is old enough to be responsible. Carl lets him live at home. To earn money to pay for damaging the Winslow house with one of his inventions, Steve plays jazz piano in a local club - after transforming into the suave Stefan Urquelle. The highlight of his show is when Laura sings a love song with his accompaniment, followed by a passionate kiss.

At a recital, Eddie and Greta's pas de deux from ""Swan Lake"" in interrupted by an ungly duckling from down south - Myrtle Urkel. Harriette, feeling dowdy, gives herself a makeover, while Eddie reluctantly enrolls in ballet lessons to improve his basketball skills. When he and his girlfriend, Greta, perform a famous ballet with the class, Myrtle Urkel arrives and takes Greta's place - both on and off the stage. Meanwhile, Harriette becomes depressed when Laura's boyfriend, Curtis, thinks that she is Laura's grandmother. She begins dressing like Tina Turner but finally comes to terms with being comfortable with her age.

Urkel volunteers as a Big Brother to a touch street kid who's mastered pick pocketing skills but harbors a secret about his reading ability. Through a charity, Steve becomes a mentor for a tough but charming inner-city nine-year-old, 3J. While tutoring him, Steve discovers that, although 3J is smart, he is illiterate. At first, 3J rejects Steve's help, preferring to survive with his natural talents as always. But Steve excites him about the wonderful worlds of imagination one can find in books, and 3J decides to make his life better by learning to read. Meanwhile, Carl finds Harriette's secret savings account book. He is upset that she hid it from him. But later, he regrets arguing with her when she gives him an expensive gift for which she was secretly saving money.

Urkel's powerful love potion prompts a sudden devotion from Laura; airline nightmares plague Carl and Harriette on their way to Nassau for a second honeymoon. When Steve casts a spell on Laura with a magical love potion, his lifelong quest for her may finally have a happy ending. Meanwhile, Harriette and Carl's plans for a romantic second honeymoon are thwarted.

Eddie and Urkel don't tap dance around the fact that Waldo is a klutz on the basketball court, so Waldo takes tap dancing lessons to improve his agility. Elsewhere, getting accepted to Harvard means the world to Laura, until she l earns her parents can't pay the tuition.

Eddie and Waldo fall victim to a scam when they saunter into a bar expecting to meet members of the Chicago Bulls ; Urkel's super glue provides Laura with a super-facial. When Eddie and Waldo go to a bar where they think famous basketball players congregate, they are astounded by the expensive bill. Meanwhile, Myra makes an organic facial treatment to help Laura get rid of a pimple. Unfortunately, Myra mistakes Steve's super glue for milk and uses it in the mixture.

The school prom brings one disaster after another for Laura. First, her date cancels; then she's parked with a dateless Urkel at the dance. The group ""Immature"" performs.

Carl gets a job acting in a movie, but feels guilty about kissing another woman.

Urkel discovers he's able to isolate and then duplicate complex molecules. In other words, he can ""clone stuff"" - which means double trouble for the Winslows.