Dawn and Piplup are hard at work on a new Bubble Beam combination, but Piplup works so hard that it passes out from exhaustion! Dawn and the gang rush Piplup to a Pokémon Center for some much-needed rest. Team Rocket is also exhausted, but not from hard work; after a well-fed week at the Pokémon Summer Academy and a stop at an all-you-can-eat restaurant, Team Rocket realizes they've put on weight. Now they're so out of shape, they're more likely to give up their seats to an elderly couple than pull off a criminal caper! Horrified, Team Rocket resolves to get back to basics and begins an exercise program.
Over at the Pokémon Center, Dawn apologies to Piplup and gets some advice from Professor Oak. While Dawn talks to other Trainers to pick up training tips, her friends perform chores to help Nurse Joy. Meanwhile, Team Rocket sneaks into the Pokémon Center and begins stealing Poké Balls from the repository. Piplup wakes up when it hears the noise; it sounds the alarm as soon as it sees Team Rocket, bringing Ash and his friends running to the scene of the crime.
When our heroes confront Team Rocket outside the Pokémon Center, Team Rocket proudly unveils their latest giant mecha. It's captured all the Poké Balls and it's too powerful to approach, but Piplup uses Bubble Beam to cloud up its windshield. Then Pikachu and Happiny recover the stolen Poké Balls, and Pikachu's Thunderbolt sends Team Rocket sailing away into the night sky—Team Rocket's back to basics plan got them a basic robot with no shielding against electricity! The next day, since Piplup is healthy again, Dawn and her friends set off for Celestic Town and the next Pokémon Contest.
Dawn is training Piplup for their next Pokémon Contest while Ash and Brock look on. Piplup is proud of his Bubble Beam routine, though soon faints from exhaustion leading the group to take him to a Pokémon Center. Once there, Nurse Joy says that Piplup will be just fine and mentions that the reason for Piplup's exhaustion is over training. Dawn is worried for Piplup's outcome, and everyone agrees to take everything a little easier.
Meanwhile, Team Rocket complains as they walk up a slight grade, with noticeable signs of putting on weight. Though a bit portly around the edges, the exhausted Team Rocket's stomachs begin to rumble, and Meowth mentions that an all-you-can-eat restaurant is up ahead. The three recount their times at the Pokémon Summer Academy, including comfy beds and eating tons of food. The three then get into a small dispute about Jessie's popularity as Jessilinda. At the buffet, Team Rocket is gorging themselves and the plates are stacking up. The three all laugh at each other for being just a bit pudgy. Jessie gets angry and institutes an immediate work out session to become a "fighting machine". They all have their dreams of success; Jessie as an actress, Meowth on Giovanni's lap and James with training. They decide to go back to the basics and become like their days of old, when they began to try to capture Pikachu. When Team Rocket is just about to leave, an old couple calls them "a couple of nice youngsters" when they give up their table to them. They feel the guilt of being nice and flee the restaurant and the whole town, sobbing and screaming all the way.
Back at the Pokémon Center, Dawn sits at Piplup's bedside and Piplup wakes up. Dawn tears as she apologizes for overworking her partner, though Piplup offers his reassurance otherwise. Piplup then falls asleep in Dawn's arms, so she returns him to bed. Dawn walks out to find Ash talking to Professor Oak who Dawn still calls "The Poetry Man". Professor was telling Ash about Gliscor’s weak spots and to pay attention to agility when raising his it. Professor Oak suggests to Dawn that she should use her time at the Center to exchange information with other Trainers and Coordinators. Dawn thanks him for the advice, and does exactly that.
Following some late night exercise, the renewed Team Rocket trio drive their fast car to the Pokémon Center. They infiltrate the Center through the ceiling before splitting into two teams: Jessie and James on one and Meowth and the other Pokémon in the other. Meowth and the other Pokémon begin to stuff stolen Poké Balls into Carnivine's mouth. Though Carnivine can't hold all the Poké Balls and spits out a couple, and the disturbance wakes Piplup up. Piplup walks into the hallway to find Meowth attempting to steal some Poké Balls, and chirps loudly to grab the attention of all the others. Team Rocket rushes outside with the loot, and Nurse Joy says that the repository is empty. Ash and his friends run out and see Team Rocket.
Team Rocket begins their motto from the old days. Jessie and James have Yanmega and Carnivine lash the twerps with a Silver Wind and Bullet Seed. Ash orders Pikachu use Thunderbolt, though Yanmega's Sonic Boom cancels it out. With a press of a button, Team Rocket’s getaway car transforms into a mecha bot. Team Rocket are thrilled with their mecha, having it unleash chaos on the people below. Piplup whips up a Whirlpool, though Team Rocket's bot punches through it with ease. Piplup then uses Bubble Beam which blocks Team Rocket's sight while Pikachu uses Iron Tail to dislodge the pod carrying the stolen Poké Balls. Brock calls out his Happiny, who catches the falling pod. Ash has Pikachu follow things up with a Thunderbolt to cause the machine to fail and explode, sending Team Rocket blasting off. In keeping with their getting back to basics routine, Meowth admits he intentionally forgot any anti-electrical features, much to Jessie's frustration.
Nurse Joy thanks Ash and friends for the help, and recommend Piplup not overdo it in the future. The group leave for Celestic Town, with Brock left in a sappy mood about having to leave Nurse Joy.