When Susie gets a gig singing at Slosh Mountain, the world's coolest water park, she gives free tickets to all the Rats. The kids are thrilled, not so much about the show, but about getting the chance to go on the mother of all rides, Whiplash Gorge. Unfortunately, Tommy and Dil soon learn they have to baby-sit Grandpa Boris after cataract surgery the exact same day.
The whole school has caught Yu-Gotta-Go fever, a role playing card game, except Chuckie. When he finally starts playing, it becomes an obsession, and he's hired by Angelica to do her chores in exchange for more cards. He becomes one of the school's elite players, but in the pursuit of an elusive card, he nearly parts with the valuable stamp collection that Chas has passed down to him.
After Stu sells an invention, he tells the kids that he's splurging on a built-in swimming pool. While digging up the yard, the construction crew unearths the Rats' old mechanical Reptar toy. The kids fondly remember it, but decide to throw it away, until, during an electrical storm, they become convinced that they've angered Reptar.
Dil introduces Angelica to the concept of karma after she deviously beats out Susie for a singing gig. When she wakes up with a giant pimple, she becomes convinced that she must change her ways in order for it to disappear before showtime. Ultimately, Angelica comes clean to Susie who takes the stage for her, and to her chagrin, learns that skin outbreaks are a matter of hormones, not fate.
It's soccer season and as per usual, Phil has soccer-on-the-brain. But when Lil casually joins the team, she surprises everyone, including herself, by instantly becoming a super star. At first Phil is excited about having another soccer-head in the family, but when Lil outshines him, he starts to resent her.
When Grandpa Lou's buddy Red challenges the kids to work his dude ranch, Tommy jumps at the chance to prove himself, and drags the rest of the Rats along with him. Finding ranch work beyond grueling, the kids are one blister away from bailing when they're invited to join a real live cattle drive.
Pangborn and O'Keats lead a life skills project to teach the students the responsibilities of marriage. Chuckie is paired with jock-extraordinaire Fridge, Angelica with Susie, and Harold with Harriet, a female version of him. Each participant learns the need for compromise, cooperation, and communication, and the chaperones learn something about each other as well.
The Rats and their mothers embark on a cross country trip in a beat up R.V. to bring Susie to New York, where she's been selected to perform in a Thanksgiving parade. Generations collide, as the moms want to expose their kids to tourist attractions, but the gang wants to assert their growing independence.