Evolution prevention

Dawn's Piplup using Bide to resist Evolution

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. Tandemaus's Evolution into Maushold also cannot be prevented this way, because it evolves without playing a cutscene.

Everstone

Main article: Everstone

In 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.

National Pokédex requirement

In Pokémon FireRed and LeafGreen, if the player has not yet obtained the National Pokédex, when a Pokémon 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.

Unevolvable forms and variants

Some Pokémon forms and variants are unable to evolve altogether despite the games being compatible with their evolved forms.

This applies to any Pikachu with the player's OT and ID in Pokémon Yellow (of which the starting Pikachu is the only catchable one in the game), 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 Pokémon Sword and Shield, Pikachu, Meowth, and Eevee with the Gigantamax Factor cannot evolve. Those Pokémon, as well as Duraludon with Gigantamax Factor, are unable to be transferred from Pokémon HOME into games other than Sword and Shield. This is to prevent them from evolving in games that do not recognize the Gigantamax Factor.

Unevolvable level 100 Pokémon

From Generation I to VII, a level 100 Pokémon is unable to evolve by leveling up. For instance, the level 100 Pokémon is unable to evolve at a certain level, or with high friendship, or knowing a certain move, among other Evolution methods.

From Generation VIII onwards, a level 100 Pokémon can evolve by consuming a Rare Candy (without increasing its level) if the Evolution requirements are met.

Unevolvable Feebas

In Generations III and IV, and in Pokémon Brilliant Diamond and Shining Pearl, a Feebas can only evolve when leveling up with 170+ Beauty. In any of those games, as stated above, a level 100 Feebas is permanently unable to evolve.

In addition, Feebas is unable to evolve if its sheen has already reached the maximum value of 255 and its Beauty is below 170. This Feebas will be unable to increase its Beauty by eating any more Pokéblocks or Poffins which would be required for its Evolution into Milotic. However, in Pokémon Omega Ruby and Alpha Sapphire, a Feebas is potentially able to reach enough Beauty and evolve nonetheless because in those games a Pokémon's contest conditions can be raised regardless of its sheen.

In Pokémon FireRed and LeafGreen, Colosseum and XD: Gale of Darkness, a Feebas cannot be obtained without trading with the Hoenn games, but although it can evolve normally if its Beauty is already high enough, it is also unable to evolve with a Beauty stat of under 170 unless it is traded to Pokémon Ruby and Sapphire or Pokémon Emerald, as there is no way to increase its beauty stat with the lack of Pokéblocks.

From Generation V onwards, except in Pokémon Brilliant Diamond and Shining Pearl, a Feebas can evolve into Milotic regardless of its Beauty condition, by being traded while holding a Prism Scale.

In the side series games

Pokémon Colosseum and XD: Gale of Darkness

This section is incomplete.
Please feel free to edit this section to add missing information and complete it.
Reason: State whether or not pressing B prevents all forms of Evolution in Pokémon Colosseum and XD

In the spin-off games

Pokémon: Magikarp Jump

Main article: Everstone → Pokémon: Magikarp Jump

In 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 Quest

In Pokémon Quest, a Pokémon is unable to evolve as long as it is holding an Everstone.

In animation

Pokémon the Series

Pokémon the Series: The Beginning

In Bulbasaur's Mysterious Garden, Ash's Bulbasaur stopped itself from evolving.

Pokémon the Series: Diamond and Pearl

In Stopped in the Name of Love!, Dawn's Piplup used Bide to stop himself from evolving and collapsed from the effort. Dawn later gave him an Everstone to prevent it for as long as he wanted.

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.

Black & White arc

In Big City Battles, White forcefully stopped Black's Tepig, Tep, from evolving by shaking him around. This was only temporary, and he evolved in the next chapter.

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.