George threatens to move out when Bill goes too far in teasing him after a fall caused when he left a large tool on the stairs. When Katherine and Cassie start to argue after discussing the situation-and after Cassie's Wandering Jew dies from not being watered-Jerry is forced to intervene to resolve the feud between the Parkers and the Papadopolises.
The family visits the Tumbleweed Ranch in Lizard Flats, Arizona, where George once went as a child. While George is disappointed at the modernization, he is happy to see that Dusty, the old cowboy who was there in the old days, is still around. After Webster hears Dusty's campfire retelling of an Indian legend about a white horse named Moonhunter, he sees a white horse that he thinks is the same one from the legend. Webster wants to catch it, offering the wranglers co-ownership in return. However, Jack, the head wrangler, has other plans.
Webster's class has to do a report on what it's like to be married and raise a child; he has been assigned an arrogant girl named Annette as his "wife," while their "baby" is an egg named Chester who meets with a tragic fate at the breakfast table.
Webster has been getting home late and not calling; George decides to ground him, but Katherine, who is now majoring in psychology, comes up with a more novel idea: that Webster act as the parent to her and George to see what it's like from their perspective.
When Katherine's mother dies of a sudden stroke, she becomes withdrawn from the world. She won't go to her classes or go out with friends or family, and she refuses to go to Webster's party even though she promised him that she would.
Webster has a dream to make a free throw from a regulation basketball court, like his favorite basketball player, Patrick Ewing of the New York Knicks. When George takes Webster and Katherine to New York, Katherine's former sorority sister gets mid-court tickets to the Knicks-Celtics game for Webster and George as well as opera tickets for the two of them. Unfortunately, things do not go as planned.
Webster travels to Hollywood to see Uncle Philip, who has been signed to do a movie musical called "Rockin' Feet." He also has a surprise for Webster: he's dating a woman named Sherette. When they visit the Paramount lot, Webster sees Sherette make her move toward the film's producer.
While at first Philip doesn't believe Webster when he tells the truth about Sherette, he eventually figures it out when his part in "Rockin' Feet" is rewritten for a woman - and that woman is her. Back in Chicago, Katherine and George's attempt at a second honeymoon is spoiled when a blizzard knocks out the power and the heat.
Webster is upset when his friends tease him about having a babysitter, so he persuades Katherine to let him stay home alone for an hour. When he gloats about this to his friends, two older boys who hear this take the opportunity to rob his house. Meanwhile, Bill hires his nephew Skippy to represent him in a lawsuit over a car accident.
When Webster throws out a chain letter that promised bad luck if he doesn't send it to 25 people, bad things start to happen. He gets a D in math, Katherine's beaded bracelet breaks, and Papa is hospitalized because of what he says is "bad luck." This makes Webster think the chain letter was right, but Katherine and George must find a way to convince him that it's just a series of coincidences.
As the Parkers' 25th wedding anniversary approaches, Webster shows Katherine a picture he took of Bill's car at a hotel. She tries to confront Bill with this, but the clumsy way she does this makes Bill think she's interested in him. Bill tells this to Cassie, who refuses to believe it, but when George hears about it and goes to talk to Cassie, Webster, who doesn't understand what they're misunderstanding, tries to explain it to Katherine who draws an equally wrong conclusion.
Katherine gets a homemade dress as a present from Webster: an unflattering lime green one that says "I Love Paris" and has a large, battery-powered, lighted Eiffel Tower embedded on it. She can't admit to Webster that she doesn't like the dress, and he wants her to wear it for a special occasion. Cassie tells her to wear it as she goes out the door and then change at the neighbors' house while Webster isn't looking. The day she chooses to wear the dress is the day she participates in an experiment where she and other students will be observing four children's ...