Misty's Poliwag evolved during a battle with
Ash Ketchum to determine who would get to keep Totodile.
Misty commented right after it evolved that its sleek skin looks great.
Misty's Poliwhirl ended up loosing the battle with
Ash's Bulbasaur and Totodile was given to
Ash Ketchum. Even though it lost the battle,
Misty said at the time that her Poliwhirl was her 'number one' Pokémon because it evolved just to help her out in a pinch.