King's Rock

King's Rock is a held item which first appears in Pokémon Gold and Silver Versions. It is a brownish-yellow crown that appears to be made out of rock. The main purpose of a King's Rock is to have Poliwhirl or Slowbro evolve into Politoed and Slowking respectively, although the method of accomplishing this differs between the main Pokémon series and spinoffs.

Pokémon series
In the main Pokémon series, if either Poliwhirl or Slowbro are traded to a different Pokémon Trainer while holding a King's Rock, they evolve into Politoed and Slowking respectively. During a Pokémon battle, if a Pokémon who is holding a King's Rock attacks their opponent, there is a 10% chance that their opponent flinches. Despite its rarity, a King's Rock can be sold for a low price of 50 at a Poké Mart, although since Pokémon Sun and Moon, this has been increased to 2,500.

In Pokémon Gold and Silver Versions and Pokémon Crystal Version, there is a King's Rock found in Slowpoke Well. There is also an 8% chance of a wild Poliwhirl, Politoed, Poliwrath, Slowpoke, Slowbro, or Slowking holding a King's Rock.

In Pokémon Ruby and Sapphire Versions, there is a 1% chance that a Pokémon with the Pickup ability obtains a King's Rock after a battle. Since Pokémon Emerald Version, only Pokémon at level 11–30 have this ability. The same wild Pokémon plus Hariyama have a small chance of holding a King's Rock, although at a slightly less common rate of 5%, which has since remained the percentage of certain wild Pokémon holding a King's Rock. In all three games, a King's Rock can be found in Mossdeep City, near Steven's house.

In Pokémon FireRed and LeafGreen Versions, a King's Rock can be found at Seavault Canyon or as a reward for completing the Trainer Tower in Mixed Mode. Only Politoed, Slowking, and Hariyama have a chance of holding a King's Rock.

From Pokémon Diamond and Pearl Versions to Pokémon Black 2 and White 2 Versions, the same wild Pokémon have a small chance of holding a King's Rock as in Pokémon Ruby and Sapphire Versions except for Slowpokes who, since the Generation IV games, no longer have a chance of holding a King's Rock.

In Pokémon Platinum Version, there is a King's Rock hidden in Celestic Town, where it can be found on a ledge near the ruins.

In Pokémon HeartGold and SoulSilver Versions, a King's Rock can be bought at the Pokéathlon Dome as a prize on Mondays, Thursdays, and Sundays for 3,000 points.

In Pokémon Black and White Versions, at Route 13, a King's Rock is one of many possible items that the player character receives from a treasure hunter. The Event Mewtwo from "Black & White - 1st Anniversary" holds a King's Rock.