Stopped in the Name of Love! (Japanese: 進化！その時ポッチャマは！？Evolution! This Time for Pochama!?) is the 122nd episode of the Diamond & Pearl series, and the 588th episode of the Pokémon anime. It first aired in Japan on April 2, 2009, as part of a one-hour special along with DP121 and aired in the United States on August 29, 2009.
When Dawn and Ash reach Sandalstraw Town, they meet two familiar friends: Kenny and Barry! Kenny plans to enter the Sandalstraw Contest, while Barry is training for the upcoming Pokémon Ping-Pong competition—but their conversation is cut short when Piplup glows as if it's ready to evolve! However, Piplup isn't well, so it's off the Pokémon Center so Piplup can rest. Dawn uses this opportunity to talk to Piplup about Evolution, but it gets upset and runs away!
Everyone splits up to search the nearby forest, and Dawn finds Piplup using Bide to stop its Evolution. She doesn't understand why it won't evolve, and that makes Piplup angry enough to run from her again. When Dawn chases Piplup deeper into the forest, she finds it stuck in an Ariados web. Dawn saves Piplup from the Ariados, but then they're surrounded by an entire swarm of Ariados! Piplup uses Bide to defeat them, and Dawn realizes this is just like the day when she and Piplup first met.
Barry and Kenny are also searching the forest for Piplup, but Barry's Empoleon and Kenny's Prinplup are kidnapped by Team Rocket's giant Piprinoleon robot! The robot finds and grabs Piplup too, so Dawn sneaks inside the robot and confronts Team Rocket. Piplup forces its way through a duct in the robot to reach Dawn and back her up; all this time, it's wanted to remain a Piplup so it can protect Dawn. Piplup uses Whirlpool to bust open the robot, and Dawn's friends arrive to provide support. With their help, Piplup sends Team Rocket shooting into the sky, and Dawn promises to always be partners with her Piplup. No Evolution needed!
Later, at the Pokémon Center, Nurse Joy gives Dawn an Everstone to prevent Piplup from evolving. Now everyone can concentrate on the Sandalstraw Contest—as well as practicing their Pokémon Ping-Pong!
As Dawn's upcoming Pokémon Contest in Sandalstraw Town approaches, she and the others stops at a local Pokémon Center. Dawn decides to train and summons all her Pokémon, knowing she only needs one more Ribbon to enter the Grand Festival. Piplup runs forward and collapses, everyone asking if he is okay. Piplup tries to get up and falls again, concerning Dawn. Barry suddenly appears and crashes into Ash as usual. Kenny also appears and after calling Dawn Dee-Dee (much to her annoyance), asks if she's entering the Sandalstraw Contest. Barry reveals that he is best friends with Kenny despite having met him only recently and that they stopped by Sandalstraw Town because Kenny plans to enter the Pokémon Contest while Barry has his eyes on the upcoming Pokémon Ping Pong Tournament. Barry shows Ash a flyer about the event and Brock mentions that a Trainer and one of his or her Pokémon will partner up as a team to enter. Barry summons Empoleon in order to train, planning to enter with it. As everyone watches, Piplup starts to glow, causing Piplup to jump around. Kenny mentions that Piplup is starting to evolve into Prinplup. Everyone's excited, but Piplup braces himself, stopping the evolution and becoming so exhausted to the point of collapse. Brock urges everyone to go to the Pokémon Center.
At the Pokémon Center, Nurse Joy checks Piplup as she reassures Dawn that Piplup only needs to rest. During dinner, Dawn mentions that it still surprises her that Piplup will evolve. Kenny tells Dawn it's no surprise considering how well she's raised him and Barry also congratulates Dawn on a good job but advises that the evolution path from Piplup to Empoleon only gets harder. Kenny then mentions that as Prinplup is double the size of Piplup, she'll have more to show off in Pokémon Contests while Ash mentions that she will need to adapt her battling style just as he adapted when Turtwig evolved into Grotle. Although Ash is skeptical of Dawn mentioning her adaptation to Mamoswine, Dawn is still excited, but Brock displays concern. Outside, Team Rocket listens in and decides to steal the Piplup evolutionary line.
During the night, Piplup wakes up and looks at himself in the window's reflection, imagining himself as Prinplup. Dawn comes up from behind and presents Piplup with food, but he refuses. Dawn reveals her excitement for Piplup's evolution, but Piplup doesn't seem enthusiastic as Dawn tries to reassure Piplup. Piplup jumps around as he begins to glow again, the evolution process starting. Dawn tries to get Piplup just let the evolution happen, but Piplup uses Bide to stop evolving, exhausting himself in the progress. Dawn questions Piplup's motives and brings up the positives of evolution, but Piplup gets angry that Dawn appears to be ignoring his unwillingness to evolve and jumps out the window and flees the Center, prompting Dawn to follow. Barry and Empoleon pressure Brock, Kenny and Ash to train for the Ping-Pong tournament (despite the fact that Brock and Kenny don't plan to enter), but Dawn shows up and mentions her situation. Outside, Brock mentions his concerns that Piplup does not want to evolve, using Bide to stop evolution and expend energy. Everyone splits up to search as Kenny summons Prinplup to help search. As Dawn searches on her own, she spots a light in the forest.
Piplup sits under a waterfall, stopping the evolution into Prinplup but collapses into the water. Dawn arrives and picks up Piplup, questioning his reason to not evolve. Piplup gets angry again and jumps out of Dawn's hands before firing Bubble Beam and running off. Dawn searches as she spots Piplup stuck in a web. She runs forward as an Ariados attacks her with Sludge Bomb. While she dodges, Piplup uses Bubble Beam to stall Ariados. Dawn runs forward as another Sludge Bomb grazes the top of her head, causing her to trip. The attack frees Piplup and sends him airborne, but Dawn quickly catches Piplup. However, multiple Ariados confront the two and all prepare to fire Hyper Beam. Just before the attacks hit, Piplup jumps forward and uses Bide to take the attacks before retaliating, sending all the Ariados flying. Piplup collapses exhausted as Dawn picks up Piplup.
As Barry and Kenny continue searching, a Bullet Seed attack knocks down Prinplup and Empoleon before two mecha arms grab them. Empoleon and Prinplup try to use Hydro Cannon and Bubble Beam, but the hands spin and disorient them as Kenny and Barry notice a large mecha. Meanwhile, Dawn carries Piplup to a lake as Piplup wakes up, Dawn thanking her Pokémon. Dawn mentions how a similar situation occurred when they first met and how Dawn chose Piplup. Ash and Brock find Dawn and are relieved that they're okay. Suddenly, another mecha arm grabs Piplup as a giant Prinplup mecha shows up, revealing the captured Piplup evolutionary line. Team Rocket recites their motto but Barry cuts them off. Ash has Pikachu fire Thunderbolt, but the mecha redirects the attack to harm Prinplup and Empoleon.
The mecha deploys tank treads and proceeds to escape, but Dawn spots Piplup and decides to run after the mecha, getting on the side. Dawn notices a hatch up top and gets in that way. While Dawn demands her Pokémon back, Piplup destroys the ventilation gates with Peck and Bubble Beam, getting into the control room with Dawn. Meowthtranslates Piplup's talk as he plans to take them down and that he wants to protect Dawn just like the first time, revealing that past events have motivated him to stay the way he is. Dawn accepts Piplup's decision and has him attack with Whirlpool, destroying the mecha and freeing everyone. Outside, Team Rocket gets up and summons Seviper and Carnivine. They attack with Poison Tail and Vine Whip, but Piplup's Bubble Beam stops both in their tracks. Piplup starts to glow again as he tries to stop the evolution, leaving him and Dawn vulnerable. James wants Piplup to not evolve to maintain the family, but Jessie opts to let it and instead present the boss with Empoleon triplets. Seviper and Carnivine rush to attack the defenseless Piplup, but Pikachu's Thunderbolt stops both Pokémon, Ash and the others arriving on site. Piplup is still immobile as Seviper and Carnivine attack again with Bullet Seed and Poison Tail, but Pikachu defends with Thunderbolt. Piplup manages to stop evolving and attacks with Whirlpool, sending Team Rocket flying away.
Dawn thanks Piplup for saving her again, and realizes that Piplup's memory of their first day together is why he wants to stay as he is, and tearfully apologizes to her Pokémon for not understanding his feelings. Piplup tells Dawn that it's ok and with her friends watching on, Dawn happily picks up her partner and best friend telling him she's happy for him to remain as her Piplup forever which delights Piplup, and the two reaffirm their bond together.
At the Center, Nurse Joy finishes tending to Piplup, Prinplup and Empoleon and the three Pokémon happily run to their respective Trainers. Nurse Joy then tells Dawn she has something for her, and Chansey presents Dawn with an Everstone, which has the power to prevent a Pokémon from evolving for as long as it wants. Dawn and Piplup gratefully accept the gift, knowing this means Piplup won't have to use Bide to prevent the evolution anymore. With the excitement over for now, Ash and Barry start training for the Ping Pong competition while Dawn and Kenny practice for the Sandalstraw Contest, everyone as determined as ever on achieving their goals.