Crossing a hill on the way to Goldenrod City, Ash and his friends notice a building nearby. As Brock is about to say what he thinks the building is, a Wooper drops from a tree and lands on Brock's neck, causing him to fall down the slope.
On the lower level, Olesia is about to teach the class of Wooper when Brock hits the ground. Wooper then jumps off Brock and Olesia asks if he is alright. Brock quickly recovers and starts flirting with her. Misty pulls him away and then asks Olesia about the buildings. She tells them that it's a preschool only for Wooper. She then tells of how she loved to raise Wooper, and how that spot was a good place to teach. Ash then goes to his Pokédex and looks up Wooper. Ash reminds himself of his previous encounter with the Quagsire. Misty then asks Olesia if they could watch her teach and she agrees. She plays the tambourine and then the Wooper start to swim and dance. Ash and Misty then admire the Wooper while Brock admires Olesia.
In the woods, Jessie is looking around for food when she finds a mushroom. James and Meowth tell her that it is poisonous. She tosses it aside and all three start to complain of how they haven't had any food for weeks. Then James says that they could call "the Boss" for money but then is told by Meowth that they spent all the money he gave them. They decide their only hope is to find a rare Pokémon.
Wobbuffet joins the trio and they start looking around for either a rare Pokémon or a snack.
Ash and his friends are having their snack when Olesia gets a call from her mom. Olesia then says that her mom needs to see her. Brock then offers to take care of the Wooper while she is away. She accepts, gives Brock a book about raising Wooper, and drives off in her Motorcycle. They head inside the preschool.
Inside, they discover the Wooper aren't in the pond. Pikachu then finds a trail of water leading deeper inside the house. They follow the trail and find the Wooper eating and all over the place. Brock then reads in the book that the best way to get Wooper to listen to you is to show affection and food. So Brock pulls out a piece of food and shows it to the Wooper. One Wooper walks up and licks him and then the rest proceed to do so too. He then reads that the second best way was to play the tambourine. Misty then remembers of how she used to play the tambourine when she was a little girl. She picks up the tambourine and begins to play it, but none of the Wooper seem to be entertained. She then puts it down and they begin to leave; she then realizes Togepi is gone. They hear a tambourine playing, and they see Togepi playing the tambourine and the Wooper following Togepi.
Misty is angry that they'd rather listen to Togepi's beat rather than her own. Brock says it's just because Pokémon know a Pokémon's beat. After all the Wooper have been returned to the pond, Brock congratulates Togepi on a job well done, and is relieved to have recovered all the Wooper. However, Misty realizes that one Wooper is missing; more specifically, Olesia's favorite one.
Brock is told to stay with Togepi and the Wooper in the pond and keep them occupied whilst Ash and Misty go look for the missing Wooper. They begin by checking the classroom, but hear a huge crash coming from the kitchen. The crash came from the missing Wooper, however, just as Ash and Misty are about to retrieve it, it runs away, dodging all their attempts to catch it and almost destroying the room in the process; Ash and Misty hurry to stop a large pile of plates toppling over, and Pikachu is almost stabbed by falling cutlery, this results in the Wooper getting away. Outside, the Wooper is seen climbing the cliff face Brock fell down. Ash and Misty once again give chase. Wooper reaches the top of the cliff before Ash and Misty do, and runs off into the forest. It is seen crossing a very rickety rope bridge across a chasm. Ash runs across but is frozen with fear when hearing the creaking beams beneath his feet, Misty and Pikachu tentatively follow. Misty tries to reason with the Wooper to return to the pond, Wooper agrees, and begins jumping up and down in excitement. This makes the bridge begin to wobble, and once again the Wooper slips through their grasp and runs across to the other side of the bridge. The bridge then breaks leaving Ash and Misty hanging and Pikachu on the top having made it across. Ash tells Pikachu to leave them and chase the Wooper.
Meanwhile, Meowth is seen complaining over a boiling pot, claiming that Mushroom soup won't have much flavor without any Mushrooms. He then notices the Wooper, and, mistaking it for a Mushroom, attempts to catch it. Jessie and James then return from their foraging, and, hearing about the "giant mushroom", start looking around for it, while the Wooper eats from their basket of mushrooms. They then spot the "giant mushroom" just as it eats the last of their mushrooms. The trio are at first angered by the Wooper, but it's cute face gets rid of this anger. Jessie decides it would be a good idea to take it for their boss, thinking he will be so happy at the sight of it he will forget about their many failures. Jessie attempts to catch it but it fails, as it already has an owner. Pikachu then arrives in Wooper's defense, and refuses Team Rocket's request to convince the Wooper to enter the Poké Ball for them. Ash and Misty then arrive, and the Wooper evades both Team Rocket's and Pikachu's attempts to catch it. Jessie then commands Wobbuffet to attack the Twerps, but it does nothing. She then sends Arbok clashing into the group, and James tells his Weezing to use SmokeScreen. Team Rocket escape in the balloon with the captured Wooper, but at that moment Olesia and Brock arrive on a motorbike and chase the balloon, Team Rocket then recite their motto. Before Brock and the others release their Pokémon to free the Wooper, Olesia thinks she can entice it to return by telling it that playtime is over and it has to go back inside. It jumps out of the net and back to the group with Arbok and Weezing following it. Wooper looks in trouble, but Olesia commands it to use Tackle attack on both of them, revealing it to be a strong Wooper. It then sends Team Rocket blasting off again.
Back at the school, Togepi had been keeping the group entertained with its tambourine. Brock asks what Olesia's secret is for raising such strong Pokémon, to which she replies that there isn't one, and the strength really comes from people not expecting the Wooper to be powerful. Brock then asks if he can stay at the school so they can both learn about Pokémon and "maybe each other", resulting in him getting dragged away by Misty. The group then says their goodbyes, and continues on their way through Johto.