Pokémon: The Series Rewrite:Indigo League Part 1

Episode 58: The Misty Mermaid

Ash decides to help with Misty's team and Misty wants to evolve her Dragonair into a Dragonite. She learns that her sisters are having a underwater ballet and ash and the group crash the party and Misty amazes everybody with her showing off and Dragonair evolves into a Dragonite. She ends up giving her Dragonite to her sisters along with her Starmie to stay at the gym for the time being. Brock evolves Vulpix into Ninetailes.