Ya See We Want An Evolution! (最強のコイキングと最も美しいヒンバス！ The Strongest Magikarp and the Most Beautiful Feebas!) is the 21st episode of Pokémon: Diamond and Pearl.
While they were walking tiredly, Team Rocket sees again the Magikarp salesman, who had tricked James by persuading him to buy some Magikarp. James tried to take his money back until Magikarp salesman made Team Rocket to buy an Evolution Machine. Meanwhile, Ash and co. visit Oralie and Haley, two coordinators that claim to have the strongest Magikarp and Feebas each one. After both Ash and Dawn's defeat by Oralie's Magikarp, Team Rocket steals Magikarp, Feebas and Pikachu and tries to evolve them. Will they succeed?
Team Rocket wander in sadness. Suddenly, a Magikarp is thrown to James. Team Rocket see the Magikarp Salesman again and James throws the Magikarp back to him. They want their money back, but the salesman offers them something else - an evolution machine. The salesman tells them the machine was a result of a years-old work. The company was bankrupt, but the salesman got the parts and built a machine of his own. The salesman offers them the machine which evolves any Pokémon at any time and any place. Team Rocket are delighted and take the machine, along with the manual. The salesman runs away, but comes back to warn them not to use the machine for a week.
Meanwhile, the heroes came to Jubilife City. A reporter asks Ash if he wants to use the evolution machine to evolve Pikachu. Ash does not want that and the reporter thinks he belongs in B league - a group of Coordinators who want to win without having their Pokémon evolved. They are known to have usually a Magikarp or a Feebas. They came to the building where the B Button League is. Two girls meet them (and Brock flirts with them). One of them is Haley and the other Oralie. They come to a room where Magikarp and Feebas are, supposedly they are very powerful. The B Button League thinks there is more than just evolution. Ash wants to join, as he does not want Pikachu to evolve. Ash wants to battle Magikarp, but Dawn wants as well, as she does not know how Piplup battles in water.
Dawn sends it and suddenly they are approached by three people (who are Team Rocket in disguise). They made a C League and want to test something. The battle is about to begin. Team Rocket plans to take Pikachu and evolve it using the machine. Piplup starts with Peck, but misses. Piplup tries with BubbleBeam and hits Magikarp, but gets tackled a lot of times and gets defeated. Now Ash has a battle. Pikachu starts with Thunderbolt, but misses. Magikarp retaliates by tackling Pikachu. James confirms that Magikarp evolves into Gyarados and Jessie would like to have a powerful Gyarados. James and Meowth like this plan a lot. Pikachu uses Quick Attack and Magikarp Tackle, though Pikachu switches to Iron Tail and the attacks collide. Ash and Haley see their Pokémon exhausted.
The pool is lowered and the C League (or Team Rocket) are pleased to have the results and want the Magikarp put in the machine to be evolved. Oralie also would like a battle with Feebas, though Ash thinks it is also powerful as Magikarp. They go to get lunch, but see the C league stealing Magikarp and Feebas. Team Rocket take off their disguises and are mistaken to be the R League. Team Rocket run away and the heroes, along with Oralie and Haley, chase them. Ash sends Staravia, who follows them. They go inside a lodge and see the evolution machine they set up. They want to evolve Feebas and Magikarp. Pikachu tries to stop them, but gets captured. They send Magikarp, but are surprised to see it did not evolve. Team Rocket put it once more, but still no Gyarados.
They try on Pikachu, but he did not evolve. Meowth reads it needs one week to function. Pikachu frees the heroes with Iron Tail. Meowth reads the machine can be used as an robot and he activates it - an explosion is made and the machine forms into a robot. However, it is unstable and gets destroyed soon enough. Magikarp tackles them and Feebas freezes them with Ice Beam. Pikachu blasts them off with Thunderbolt. The heroes leave the B button league and go away.