Bye Bye Psyduck - S2.E11

After stopping on another island to rest, Misty notices her Psyduck's tail is glowing, a nearby trainer says it may mean it is time for it to evolve. So Misty challenges her to battle and when she finds she has a Golduck, she easily beats the trainer. However, Team Rocket has other plans. Later, Golduck turns out to be a wild Pokémon as Misty's Psyduck makes an appearance.