Pokémon Heroes (2002)

“On a mission they never expected. To a world they never imagined. An adventure you'll never forget.”

Ash, Pikachu and the gang try and stop a pair of thieves hiding out in the canals and alleyways of Altomare, the age-old water capital. Joining the adventure are two new legendary Pokémon, a pair of siblings named Latias and Latios, who serve as peacekeepers and protectors of the Soul Dew — a priceless treasure with a mysterious power.