Water Park is the 16th and final episode of season 1.

Plot

Malcolm and Reese spend the day fighting at a water park; Francis gets into a different kind of pool math with Spangler; and Dewey stays home with an odd babysiter.

Summary

Lois is prepping Hal for a family trip to the water park and unfortunately Dewey can't go because of an ear infection. He's upset about it, while Lois tries to console him and soon mentions that he needs to stop sticking dirty things in his ears. Unfortunately the Wilkersons have a hard time hiring a babysitter for Dewey, due to Malcolm and Reese's countless misbehaving themselves towards their previous babysitters. They eventually manage to hire a stern babysitter named Mrs. White(Beatrice Arthur) and the family is off to the water park.

At Marlin Academy, Spangler is gloating after winning against Francis in a game of pool. However, he soon gets suspicious when he learns that his most rebellious student has been plotting something. Spangler finds out from the local police that Francis has been out at local bars hustling, and is upset that he has been letting him win. He insists that Francis play his best game of pool against him, while his fellow cadets tell him he has to lose so Spangler doesn't get upset. Because if Francis wins, the cadets are going to torture him with hours of educational programing on PBS. They end up in a battle as to who can play a more spectacularly bad game of pool, pulling trick shots to scratch on the eight-ball. Spangler loses, but the cadets end up not caring at the end.

At the water park, Lois and Hal are trying to enjoy a "tropical" vacation, while Malcolm and Reese are at war. Soon they ruin their parents' tropical vacation with their fighting and Lois soon yells at them at the top of the Liquidator water slide. As she continues to yell, Malcolm looks at Reese and encourages him to push her down the slide. He tries to refuse and Lois comes to suspect something is wrong. Sure enough Malcolm pushes her down the slide and Reese tells him that was the bravest thing that he's seen him do. However, Lois whom somehow manages to hold on to something, grabs both the boys and they slide down the water slide together. As she continues yelling at Malcolm and Reese, Lois tells them "This is the last time, I'm taking you boys anywhere." They come out of the slide splashing Hal and everyone else.

At the house, Dewey bonds with Mrs. White and they start enjoying many activities together. After they dance around the kitchen, she has to be taken away in an ambulance, and he goes chasing after a red balloon being carried by the wind and winds up being in lost in a Chinatown. Soon he follows a paper bag being carried by the wind.