From Bulbapedia, the community-driven Pokémon encyclopedia.
Evolution prevention refers to certain methods to stop a Pokémon from evolving.
In the core series games
B button
 | This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: State whether it is possible to stop any other Pokémon evolutions by pressing B. The evolutions of these Pokémon are not currently covered by this section: Milcery, Galarian Yamask, Galarian Farfetch'd, Stantler, White-Striped Basculin, Hisuian Qwilfish, and several evolutions from being exposed to items (Galarian Slowpoke, Applin, Sinistea, Kubfu, Scyther into Kleavor, Ursaring, Charcadet, Poltchageist, and Duraludon) |
In the core series games, the player can press B during the evolution cutscene to prevent any of the methods of evolution triggered by gaining a level in battle or by consuming a Rare Candy. This includes but is not limited to leveling up at or above a certain level, or with high friendship, or in certain locations, or knowing a certain move, holding a certain item, and so on.
However, pressing B does not work to prevent evolutions from Evolution stones or from trades.
Everstone
Main article: EverstoneIn all core series games with the held item feature, a Pokémon holding an Everstone is unable to evolve using certain methods of evolution. This item prevents all the evolution methods triggered by leveling up. It also prevents a Pokémon from evolving by trade, except this does not work in Generation III due to a glitch. From Generation IV onwards, a Kadabra still evolves into Alakazam when being traded while holding an Everstone due to an explicitly programmed exception. Only in Generations II and VIII, the Everstone prevents evolution from an Evolution stone.
For more details, see Everstone → Effect.
Evolution exceptions
In Pokémon FireRed and LeafGreen, if the player does not have the National Pokédex, when a Pokémon in the Kanto Pokédex meets its evolution conditions but its evolved form is not in the Kanto Pokédex (for example, Chansey's evolution into Blissey), it will attempt to evolve but fail.
Some Pokémon are unable to evolve altogether despite the games being compatible with their evolved forms. This applies to the Pikachu in Pokémon Yellow, the Spiky-eared Pichu in Pokémon HeartGold and SoulSilver, the Cosplay Pikachu in Pokémon Omega Ruby and Alpha Sapphire, Pikachu in a cap from Generation VII onwards, and the Partner Pikachu and Eevee in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!.
In the spin-off games
Pokémon: Magikarp Jump
Main article: Everstone → Pokémon: Magikarp JumpIn Pokémon: Magikarp Jump, the player begins the game with one Everstone, which prevents Magikarp from evolving into Gyarados. This item can be cracked and broken by tapping Magikarp in quick succession.
Once it is broken, Magikarp can evolve on reaching Level 20 or higher. This will cause the Magikarp to retire, and a new one must be caught.
Pokémon Quest
Main article: Everstone → Pokémon QuestIn Pokémon Quest, a Pokémon is unable to evolve as long as it is holding an Everstone.
In the manga
Pokémon Adventures
Yellow arc
In Can't Catch Caterpie!, Yellow reacted with shock and dismay when her Ratty evolved into Raticate due to the fact that she had no idea what is evolution in the first place. Blue then informed Yellow that it is possible to cancel a Pokémon's evolution by using the Pokédex.
In The Might of... Metapod?!, it was revealed that since Blue taught Yellow how to cancel a Pokémon's evolution, she had been often cancelling the evolution of her Pokémon by using Red's Pokédex. However, with the Pokédex no longer in her possession, several of her Pokémon evolved at once during the battle against Lance: Kitty evolved into Metapod and then Butterfree, Dody evolved into Dodrio, Omny evolved into Omastar, and Gravvy evolved into Golem.
In the TCG
In the Pokémon Trading Card Game, several card effects prevent a Pokémon from evolving. For instance, Spiritomb has an attack named "B Cancel" whose name refers to pressing B to cancel an evolution in the core series games.
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