S12E45 : Sticking with Who You Know!

A Pokémon scientist creates a love machine which will create a friendship between his water and electric Pokémon (Quagasire and Magnemite) but a flaw in it creates the friendship between the water and electric Pokémon all over that area. Unfortunately, Ash's Pikachu and Dawn's Piplup also comes under this area, thus becoming literally inseparable. The team somehow finds about this machine and helps the scientist to achieve his goal without the machine, thus helping their Pokémon to be free from their trance becoming normal again.