Harry is stuck inside the mansion in a parody of Home Alone. Most of this episode is Fred explaining what Maniac Mansion is about. He tells stories of pilot episodes, and how the show developed from there. He then meets Casey and Idella, and finds out that the script has changed so that only Harry is in it. He's angry and tells Ike and Turner that they have to write themselves into their own script. Later, Tina comes by and makes him realize that the show is about everyone through flashbacks of the first season. At the end, the family decides that they need to make it look like a television show again. They have Fred wake up from a nightmare about his family being a TV show, as they sometimes did in the first season.

Casey complains about how the living room looks, and wants to redecorate it. Fred doesn't want to, but eventually gives in and tells Casey to go ahead. Fred flashes back to his 18th birthday, and remembers how happy he is with the living room. The movers come to get the couch, but on the way out Turner jumps on it. Casey tells him that they'll keep the furniture, but gives Fred a lecture about how selfish he's being. Fred then flashes back to his birthday when he was drafted. He then decides that the family should make their own history as a new generation of Edisons. The show ends with everyone enjoying the furniture Casey picked out.

Harry watches a talk show that Idella hates. She tells him that he has as much talent in him as all of their guests put together. This inspires him to go down to the studio where the show is taped. When Lanny Reese (the host) realized who Harry was, he trapped him in a glass. The family was worried about where Harry was, and they though he was dead. That night they watched the Lanny Reese show and saw Harry trapped. Harry pretended to be dead, and flew out when Lanny lifted his hand off of the glass. He made his way home, and the family was glad to have him back.

Turner has been exceptionally bad lately, and after breaking a cookie jar Casey sends him to his room. Ike tells him that he should fake running away from home to teach his parents a lesson. After Ike left, Turner shrinks down to microscopic size and falls into his shoe. Fred had performed this shrinking experiment on him earlier, but the effect was delayed. Ike realized the mistake of telling Turner to run away and goes back into his room. When Ike can't find him, he thinks he really ran away from home. Ike tells Casey what he did, and the family discusses whose fault it was. Later on they hear a crash, and go upstairs to find Turner back to his normal size.

Fred invents a computer called RD-12 that has true artificial intelligence. Fred and Tina feed him scientific data to improve his knowledge. Everyone else starts talking to him about other aspects of life, which he finds more interesting. So now he wants to leave and explore things other than science. After arguing with the family, Fred gives in and lets him go.

During dinner, a cab gets into an accident outside of the house. It turns out that Jose Ferrer was in the cab and has hurt his ankle. So the Edisons let him stay at the house while Fred fixes his foot. When Fred experiments on him, he messes up and gives Jose rabbit's feet. Fred eventually figures out a way to bring his regular feet back, and Jose leaves.

Tina and her friend Val go out to see a movie. During the show, Val acts mad at Tina. Val feels that her boyfriend is falling all over Tina and that she is stuck up. Later, Tina accidentally eats one of Fred's experiments that makes her really ugly. Tina then locks herself in her bedroom and refuses to come out. After realizing her mistake, Val comes over and apologizes for what she said. Tina and her make up, and the effect wears off.

Fred finds a book in the lab called ""My Forbidden Experiments"". He decides to perform one of them, and creates an odd slime creature which he doesn't know about. When looking for his headphones, the slime attacks Keifer and makes him act strange. Now all Keifer wants to do is help out Fred in the lab on an experiment that absorbs oxygen. Fred figures out that Keifer is now an alien creature who wants to get rid of all the oxygen on earth. Fred then tricks him into the andromeda chamber, and changes him back to normal.

Lenny met a girl in France and they are planning to get married. She comes to meet the family, and things go well. Later, Lenny tells Teri he can't marry her because he could die soon. The doctor told him if he gets hit in the head one more time, that would be it. He eventually decides to go through and have the wedding anway. During the ceremony, Lenny drops the ring and he bends down to pick it up. Teri goes to get it at the same time and they bump heads. The collision puts Lenny into a coma, and everyone thinks he's dead.

Lenny is in a coma at the local hospital. The doctor tells the family that there's nothing he can do except wait until Lenny decides to come out of his coma. In a dream, Lenny meets St. Ian. After helping him out, Lenny convinces St. Ian to let him go back. Lenny wakes up and the show ends with pictures from the wedding reception.

Fred develops a machine that increases human intelligence. Fred tries it on himself and likes the results. However, he steadily becomes more dependant on the machine and uses it all the time. It gets to the point where he's obsessed with knowledge and loses touch with the family. Fred then realizes he needs help and gets rid of the machine.

A new neighbor moves in, and visits the Edisons. He's part of the witness relocation program because he ratted on a mob family. He thinks Fred is Tony, who was part of the gang. He also thinks that Fred is going to kill him. Fred sets him straight, and he's quite relieved. Later, two real men from the gang come looking for Hudgie, and get scared when they see Fred. They decide to meet at a local diner, and Hudgie has Fred pretend to be Tony. With the help of Harry, Fred and Hudgie fool the mobsters. He then moves to Calcutta to avoid being caught again by the gang.

Casey's parents are having a party for their 50th wedding anniversary. Everyone's going except for Fred, who sprained his toe and is stuck in bed. Right before they leave, a woman comes to the door and claims to be Casey's biological mother. After talking to her, Casey decides to go to her other parents and leave Fred with her mother at home. Fred starts noticing Dolly is acting strange, and later figures out that she's crazy. He attempts to knock her out, but she ends up noticing him and they start to fight. At that same moment, Casey and the rest of the family come home and break it up. It turns out that the woman had amnesia and thought she was Casey's mom.

Ike likes a girl in school, so he asks her to the dance. She agreees, and everything seems to be going fine. However, at the dance Cherie tells him her dad got a job offer and they'll have to move. She then leaves, and Ike is by himself on the dance floor. Seeing that he's depressed, Tina comes over to dance with him, and Ike feels a little better.

Fred's friend Eddie from high school shows up at the mansion. He's an actor who has had problems with drinking in his past. After getting shot down for another big role, he decides to drink again. He then shows up at Tina's play drunk and completely embarrasses her. Fred tells Eddie about his problem, so he tries to go without drinking for a week. He succeeds, and decides to keep a smaller role in a movie. Fred decides to throw a party to celebrate. Later, Eddie receives a telegram saying that he lost the job. He then shows up at the party seemingly drunk, but is just acting. He then tells everyone that Fred made him realize he was an alcoholic, and he will remain sober from now on.

Tina asks Fred if she can go on a ski trip, and he says yes. However, she'll have to watch Turner and Ike when everyone else goes on vacation. As soon as they leave, Ike calls all his friends and tries to have a party. She tells Turner to stop Ike, but he doesn't think he can. After Turner throws Ike across the room, he realizes his own strength. Since he has power over Tina and Ike, he makes them his slaves. To scare Turner and Ike into doing what they're told, Tina pretends that she's made herself super strong in the andromeda chamber. Ike and Turner then clean up the house and start obeying Tina. After realizing what a good job Tina did, Fred lets her go on the ski trip.

Casey gets a call from Allasyn asking if she'll watch her sister's baby. Casey agrees, but wishes she didn't because the baby is colicy. Turner's friend tells him that the family will only pay attention to the baby, and he gets worried. After finally putting the baby to sleep, Turner goes into his room and makes noise, which wakes the baby up. He picks it up so it will stop crying, and the everyone comes into the room. After seeing the baby resting again, they tell Turner that the baby likes him the most because he's the only one that could get it to stop crying. This makes Turner feel better, and he doesn't have any more problems with the baby.

Idella's Aunt Hildie announces that she's coming to visit, but Idella doesn't want her to. When the rest of the family asks why, she flashes back to when she was raised by her aunts. Aunt Hildie doesn't want Idella to end up alone like she is, and tries to fix Idella up with some men. They all go bad, and Idella moves to New Orleans. She then met and married Harry. When Aunt Hildie found out, she came to visit them. After she meets Harry, she hates him and wants Idella to move home. Idella refuses, and she leaves angry. Right when Idella finishes the story, Aunt Hildie shows up with her long lost husband. She says that when he came back she was a changed woman and isn't mad at Idella any more.

Fred performs an experiment from a book called ""My Forbidden Experiments"". At first nothing happens, so he leaves. Later on, the machine works and an elf-looking guy comes out from another dimension. After going upstairs, he finds out that no one can see him except Turner. The next morning Fred and Casey find the kitchen ransacked. They blame Turner, who then blames Falslag. Since they can't see him, they think Turner made up an imaginary friend to take the blame. That night, Falslag tries to go back where he came from. Turner goes down to help him and makes a lot of noise. When Idella, Fred, and Casey come down, they blame Turner for turning the machine on. He then had them clap their hands to show they believed in Falslag, and he magically appeared before their eyes. They all apologized to Turner, and Fred promises to find a way to send Falslag back.

Idella goes to a psychiatrist because she's been having problems with Harry. She starts telling her story, but stops because she doesn't want to reveal that Harry is a fly. Fontanna recommends that she should spend time at the house to better understand Idella's situation. The family agrees, but are also worried about letting Harry's secret out. They eventually do, realizing that it's the only way for Idella to work everything out.

In the future, Tina is talking to her daughter about her new group of friends. Tina is concerned that she is dropping her old friends for this snobby new group. To help her out, she tells a story about a similar situation she was involved in. Some of Tina's wealthy friends saw her house and wanted to hold a fashion show in it. When the comittee comes over to review the house, Tina acts like she's embarrassed of her own family. Even though the comittee turned her down, she wouldn't have excepted it anyway after realizing how snobby she was acting. She then apologizes to the rest of the family.