The Gates of Warp!

S24, E41: When Dawn’s Piplup is taken through a mysterious portal by someone who looks just like her, she asks Ash to help, and Goh and Chloe come along. And when an unusually competent version of Team Rocket emerges from another portal and steals Lucario and Inteleon, Dawn and Goh chase them into a parallel world—a world without Pokémon! They meet the other Dawn, who explains that time in her world is running backward, causing Pokémon to forget moves, devolve, and even become Eggs. After doing some research with Sinnoh Champion Cynthia, Ash and Chloe arrive in the other world as well! Can they solve this mystery?