Gloom's branchedevolution family as demonstrated in the anime: both of Gloom's potential evolutions require an evolutionary stone.
Evolutionary stones may be used at any time, and cause instant Evolution in the Pokémon they are used on, which cannot be canceled. All evolutionary stones are applied directly to a Pokémon and are consumed upon the Pokémon's Evolution.
Many Pokémon that result from a stone-based evolution have vastly different level-up learnsets than their pre-evolutionary forms, with several learning no moves after Evolution at all.
In Clefairy and the Moon Stone, a giant Moon Stone appeared deep within Mt. Moon, being worshipped by a group of Clefairy who lived there. It was soon stolen by Team Rocket, and ultimately ended up being blown up; the shards from the shattered giant Moon Stone rained down on the Clefairy and caused some of them to evolve into Clefable. In this episode, the characters speculated that the Moon Stone was how various Pokémon—Clefairy in particular—arrived in the Pokémon world.
In Electric Shock Showdown, Nurse Joy gives Ash a Thunderstone so that he could evolve his Pikachu in order to defeat Lt. Surge's Raichu. Pikachu, however, refused the offer. Ash kept the Thunderstone in case Pikachu ever wanted to evolve; however, in Pika and Goliath!, a similar scenario occurred and Pikachu still refused to evolve. Seeing his determination to not evolve, Team Rocket stole it, planning to sell it.
The remaining Generation I evolutionary stones made their debut in The Battling Eevee Brothers, as part of a collection held by the Eevee brothers. Additionally, two of the Eevee brothers offered a Fire Stone and Thunderstone to Brock and Ash to evolve their respective Vulpix and Pikachu, though both refused.
In Once in a Mawile, a Water Stone belonging to Samantha appeared, which Brock's Lombre used to evolve into Ludicolo. This is the first time that a main character's Pokémon evolves via an evolutionary stone on-screen, although it is likely that James's Weepinbell was evolved using a Leaf Stone prior to The Breeding Center Secret.
Ursula used a Fire Stone and a Water Stone to evolve her two Eevee in Last Call, First Round!, making them a Flareon and Vaporeon, for use in the Grand Festival.
Ash had to find a Thunder Stone as part of a scavenger hunt in Climbing the Tower of Success!. He came across a young man in possession of one who tried to toss it to him from a long distance. The Thunder Stone nearly came in contact with Pikachu but he jumped out of the way just in time leaving Ash to catch it.
A Thunder Stone appeared in To Catch a Pokémon Smuggler! as a part of Clemont's explanation of how Pokémon Evolution works, Pikachu's evolution into Raichu working as an example of stone-induced Evolution.
A full set of evolutionary stones was seen on display in a stone shop in Geosenge Town in The Cave of Trials!. In addition, an unnamed Trainer used a Sun Stone purchased from the shop to evolve his Helioptile into Heliolisk. Clemont then revealed that he had also used a Sun Stone to evolve his own Helioptile into Heliolisk.
Evolutionary stones do not seem to be required for evolution in the anime as they are in the games. James's second Weepinbell evolved without a Leaf Stone in Here's Lookin' at You, Elekid. In addition, Pokémon that evolve via proximity of evolutionary stones apparently seem to control their evolutionary urges and physically touch the stone without evolving, as evidenced by Pikachu whacking away the Thunder Stone when refusing to evolve the first time, as well as a Clefairy holding onto a Moon Stone for prolonged periods of time before delivering it to the larger Moon Stone without evolving.
The focus of the chapter To Evolve or Not to Evolve, That Is the Question! was evolutionary stones. Misty hoped to buy a Water Stone for her Poliwhirl in Stone Town, a town on Dream Island where all the evolutionary stones in the Pokémon world come from. However, she couldn't afford one, remarking that an inexpensive one might make the evolution go bad.
Misty was later given a Water Stone by Mikey, who was being pressured to join the "Knights of the E Stone", a club which requires members to own a Pokémon evolved by an evolutionary stone. By battling club members, Ash and Mikey proved to the club leaders that Pokémon which have evolved by evolutionary stone are not necessarily superior to their unevolved counterparts.
A Moon Stone was first mentioned by Professor Oak in Gyarados Splashes In! as a rock with a crescent moon-shaped indentation that boosts a Pokémon's power immensely. In the next round, Raging Rhydon, Team Rocket searched for one in Mt. Moon, however, it was Red who eventually found it. Later on, Red used this Moon Stone to evolve Green's Clefairy during the Silph Co. showdown with Team Rocket.
In The Kindest Tentacruel, the Pokémon Fan Club Chairman told Yellow about a legend of an underwater dome at the bottom of Vermilion Harbor, housing a set of evolutionary stones which, unlike normal stones, did not disappear after making a Pokémon evolve, allowing them to be used repeatedly. The cause of Red's Poliwhirl's evolution had been one of these said stones, proving the legend to be true. Yellow was later led to the dome by a wild Tentacruel, finding a Leaf Stone in it, but the Fire, Thunder, and Water Stones were missing. Later, it was revealed that Giovanni had given them to Red so he could freely evolve and devolve his Eevee.
In Omega Alpha Adventure 0, Sapphire's Kirly evolved into a Gallade due to a Dawn Stone hitting him while training with Rara, who had evolved into a Gardevoir. Later, Steven found another Dawn Stone on the ground.
The Moon Stone and Dusk Stone are featured in the Pokémon Trading Card Game on a Trainer card and on Pokémon cards as held items. These held items work in the same fashion as Poké-Bodies, in that the effect the item provides is active whenever the Pokémon is in play. The following is a list of cards named or including Moon Stone or Dusk Stone.
Evolutionary stone cards Cards listed with a blue background are only legal to use in the current Expanded format. Cards listed with a green background are legal to use in both the current Standard and Expanded formats.
Only Grass-type Pokémon evolve using the Leaf Stone.
Pansage is the only Pokémon that evolves via Leaf Stone that has only one type, and Simisage is the only Pokémon evolved via Leaf Stone that has only one type.
The Fire Stone is the only stone not used in a three-stage evolutionary line.
All Pokémon that evolve with the Fire Stone are in the Field Egg Group.
Through a glitch in the Generation I games, Pokémon that would normally require an evolutionary stone to evolve can be evolved without it, provided that the Pokémon levels up in the battle and the player has sent out a specific Pokémon in the same battle.
The Dawn Stone induces Evolution in only two Pokémon species, Kirlia and Snorunt, the fewest of any stone.
Both evolutions only work if the Pokémon is of a specific gender.
Both evolutions were introduced in Generation IV (along with the Dawn Stone itself).
The Dawn Stone is the only stone that only evolves Pokémon introduced in a single generation (Generation III).
It is also the only stone not to evolve any new Pokémon in Generation V.
Though six Pokémon families evolve with Moon Stones, only the four introduced in Generation I can be caught in a Moon Ball, which are only acquirable from Kurt in Azalea Town.
The Oval Stone is the only evolution-inducing item with "Stone" in its English name which is not an evolutionary stone.