Pokémon S12E40 — Gone With the Windworks!
Overview
Lyra and Khoury have joined Ash, Dawn and Brock on their journey across the Sinnoh region. However, while Dawn trains for the Lilypad Town Pokémon contest with her Cyndaquil battling Ash's Grotle (with Piplup stealing Cyndaquil's poffin and getting into a fight), Lyra loses her Marill, which seems to have gone to the Valley Windworks. The group make for the Windworks immediately, but Magnemite appears out of nowhere and attacks. Then, they find Marill in the basement storage room only to get locked in. After a few unsuccessful attempts to open the locked door, Ash and his friends are finally free after Pikachu cancels the lockdown by using Thunderbolt on Team Rocket and restoring power to the Windworks. Having found Lyra's Marill, Ash and his friends are confronted by Team Rocket and their giant Magcargo Cannon, but Pikachu saves the day by using Thunderbolt. (Piplup pushes Cyndaquil to the side an gets into another fight)