Pokémon: Indigo League

The Evolution Solution (1x68)

Air date: Oct 15, 1998

Ash goes to Seafoam Island to help Professor Oak to discover the mystery of how Slowpoke evolves into Slowbro. There, Professor Westwood V is also trying to solve the mystery. Jessie captures Shellder, and tries to rush a Slowpoke's evolution, forcing Psyduck to stall the evolution.