Poliwhirl

Poliwhirl is a frog Pokemon. It is the evolved form of Poliwag. Poliwhirl, when it evolves, the swirl on its stomach changes direction. A Poliwag's swirl goes counter clockwise. It then changes to going clockwise when it evolves.

What Poliwhirl evolves into depends on a specific item that is used on it. When a Waterstone is used on it, it evolves into a Poliwrath, a dual Water/Fighting type Pokemon. But when it's holding a King's Rock, it evolves into a Politoed.