Evolution plays a huge role in Game Freak's Pokemon series; serving not only as a means of making a Pokemon stronger but also obtaining a brand new form of it. Back in the days of Pokemon Red and Blue, evolving a Pokemon by trading it or using an evolution stone was about as complicated as it got, while each Pokemon typically had no more than two additional forms (if any).
These days, however, some of the evolutionary lines found throughout the Pokemon series have become incredibly complicated, with multiple branches and increasingly bizarre methods of inducing evolution added into the series. Not all of them are quite beyond comprehension, but there are perhaps one or two of them that would have left even Charles Darwin scratching his head.
Updated December 18, 2022, by Tom Bowen: The ninth Generation of Pokemon games brought with it over one hundred new Pokemon, many of which belong to complicated evolutionary lines. Some require players to use a particular move a certain number of times, while others depend on which of the two Gen 9 games the player opted for. They join a host of pre-existing Pokemon with complex evolutions and equally bizarre genetic lines. Many of these Pokemon are able to evolve into multiple forms, with the outcome typically tied to when, where, or how the evolution is triggered.
12 Wooper
There's perhaps an argument to be made that Wooper is a little similar to the likes of Vulpix and Meowth. All three Pokemon have regional forms, which in turn have their own unique evolutions. However, where Vulpix and Meowth simply evolve into regional versions of their regular second-stage forms, Paldean Wooper instead evolves into a brand-new Pokemon.
When a Johtonian Wooper reaches level 20 it will evolve into the loveable and dopey Quagsire, but there is no such thing as a Paldean Quagsire. Instead, Paldean Wooper will evolve into Clodsire at level 20; an equally dopey yet very different-looking Pokemon to Quagsire. It's also a Poison/Ground-type rather than a Water/Ground-type, meaning that it behaves very differently in battle.
Wooper Evolutions
- Wooper -> Quagsire: Reach level 20.
- Paldean Wooper -> Clodsire: Reach level 20.
11 Sneasel
Wooper is not the first Pokemon whose regional form has its own evolution, far from it, in fact. Another example can be found in the 2022 title Pokemon Legends: Arceus, in which Hisuian Sneasel and its brand-new evolution Sneasler made their debut. The latter even ended up playing an important role in the game, with players able to use it to climb mountains.
Interestingly, the methods for evolving Sneasel and its Hisuian counterpart are actually incredibly similar, though there is one key difference. To evolve Sneasel into Weavile, players will need to use a Razor Claw during the night. To evolve Hisuian Sneasel into Sneasler, players will again need to expose it to a Razor Claw, only this time, they'll need to do so during daytime hours.
Sneasel Evolutions
- Sneasel-> Weavile: Use a Razer Claw during the night.
- Hisuian Sneasel-> Sneasler: Use a Razer Claw during the day.
10 Toxel
There were quite a few Baby Pokemon added to the Pokedex following their introduction in Pokemon Gold and Silver. After Gen 4, however, there was a rather long gap without any new additions. In fact, it would not be until Gen 8 and the introduction of Toxel that players would finally get a new baby Pokemon to raise; and it's quite a unique one at that.
Which form of Toxtricity a player's Toxel will evolve into upon reaching level 30 is entirely dependent on the Pokemon's nature. Bashful, Bold, Calm, Careful, Gentle, Lonely, Modest, Mild, Quiet, Relaxed, Serious, or Timid Toxels will evolve into the Low Key Form of Toxtricity. If the Toxel has an Adamant, Brave, Docile, Hardy, Hasty, Impish, Jolly, Lax, Naive, Naughty, Rash, Sassy, or Quirky nature though, it will instead evolve into the Amped Form.
Toxel Evolutions
- Toxel -> Toxtricity (Low Key Form): Reach level 30 with a Toxel that has a Bashful, Bold, Calm, Careful, Gentle, Lonely, Modest, Mild, Quiet, Relaxed, Serious, or Timid nature.
- Toxel -> Toxtricity (Amped Form): Reach level 30 with a Toxel that has an Adamant, Brave, Docile, Hardy, Hasty, Impish, Jolly, Lax, Naive, Naughty, Rash, Sassy, or Quirky nature.
9 Rockruff
In many ways, Rockruff is like a simpler version of Eevee, although without anywhere near as many evolutionary branches. The rock-type Pokemon has three possible evolutions and these are determined by the time of day that it evolves. All three of them effectively lead to the same Pokemon, although Lycanroc has three different forms which each have their own distinct appearances and move sets.
Its Midday form can be obtained by reaching level 25 during the daytime and its Midnight form is acquired by instead evolving Rockruff at night. Lycanroc's third and final form requires Rockruff to have the Own Tempo ability and then evolve between either five and six PM in the Gen 7 games or seven and eight PM in Gen 8.
Rockruff Evolutions
- Rockruff -> Lycanroc (Midday Form): Have Rockruff reach level 25 between 06:00 and 18:59.
- Rockruff -> Lycanroc (Midnight Form): Have Rockruff reach level 25 between 20:00 and 05:59.
- Rockruff -> Lycanroc (Dusk Form): Have Rockruff reach level 25 between 19:00 and 19:59.
8 Tyrogue
There were plenty of choices to be found in the first generation of Pokemon games; starting, of course, with whether to play through the Red or Blue version of the game. Players next had to choose their starter Pokemon and then later, whether they wanted the kicking machine that is Hitmonlee or the powerful puncher Hitmonchan. This choice became a little less straightforward, however, when the second generation of Pokemon games arrived.
Not only did Game Freak introduce the baby Pokemon Tyrogue, but also a third evolutionary form in the shape of Hitmontop. Rather than using evolutionary stones or something simple to determine what Tyrogue would evolve into though, the developers instead tied it to the Pokemon's attack and defense stats. If Tyrogue's attack is higher than its defense when it reaches level 20, it will evolve into a Hitmonlee, but if its defensive stat is higher it will instead become a Hitmonchan. The only way that it can evolve into a Hitmontop is if its attack and defense stats are equal.
Tyrogue Evolutions
- Tyrogue -> Hitmonlee: Have Tyrogue reach level 20 while its Attack is higher than its Defense.
- Tyrogue -> Hitmonchan: Have Tyrogue reach level 20 while its Defense is higher than its Attack.
- Tyrogue -> Hitmontop: Have Tyrogue reach level 20 while its Attack is the same as its Defense.
7 Pichu
Having started out with a fairly straightforward evolutionary line, Pikachu's evolutions have become increasingly complex since the days of Gen 1. In the original games, players could evolve their Pikachu by using a Thunder Stone, which would see it turn into a Raichu. This all changed in Gen 2 though, with the introduction of baby Pokemon.
A pre-evolved form of Pikachu known as Pichu was added to the games, with players needing to level up their Pichu with the highest possible friendship stat in order to evolve it into a Pikachu. Gen 7 made things even more complex with the addition of Alolan Raichu, which can only be obtained by evolving a Pikachu with a Thunder Stone while in the Alola region.
Pikachu Evolutions
- Pikachu -> Raichu: Use a Thunder Stone on Pikachu in any region other than Alola.
- Pikachu -> Alolan Raichu: Use a Thunder Stone on Pikachu in the Alola region.
6 Poliwag
When Poliwag first arrived in Gen 1, its evolutionary line was fairly simple; with the tadpole-like Pokemon evolving into Poliwhirl at level 25 and then Poliwrath when introduced to a water stone. That changed a little though with the introduction of an additional evolutionary form in Gen 2.
Now, rather than having to evolve Poliwhirl into a Poliwrath, it's possible to instead evolve it into the pure water-type Pokemon Politoed by trading Poliwhirl with a friend. It's not quite that simple though, as the Poliwhirl also needs to be holding the King's Rock item at the time of the trade.
Poliwhirl Evolutions
- Poliwhirl -> Poliwrath: Use a Water Stone on Poliwhirl.
- Poliwhirl -> Politoed: Trade Poliwhirl while it's holding a King's Rock.
5 Mime Jr.
Back when Pokemon first broke onto the scene, there was no Mr. Mime evolutionary line to speak of; only Mr. Mime himself. That all changed in Gen 4, however, with the introduction of Mime Jr. Even then though, it was far from complex; with the Baby Pokemon evolving into his adult form by leveling up while knowing Mimic.
Where things started to get a little complicated was in Gen 8 with the introduction of a Galarian form of Mr. Mime and an additional evolutionary stage. Mr. Rime can only be obtained by getting a Galarian Mr. Rime up to level 42, while Galarian Mr. Mime himself can only be acquired by evolving Mime Jr. in the Galar region.
Mime Jr. Evolutions
- Mime Jr. -> Mr. Mime: Level Mime Jr. up in any region other than Galar after teaching it Mimic.
- Mime Jr. -> Galarian Mr. Mime: Level Mime Jr. up in Galar after teaching it Mimic.
4 Wurmple
While Gen 1's moth and butterfly-like Pokemon each have their own distinct evolutionary lines, their Gen 3 equivalents are instead evolved from the same Pokemon. Bizarrely though, there's no way for players to tell which branch of the evolutionary line they'll be taking until the first evolution takes place.
Whether or not Wurmple will evolve into a Silcoon or a Cascoon depends on the Pokemon's personality value; a stat that players have no way of seeing without hacking the game. Thankfully, this evolution takes place at level 7, meaning that they at least won't have to wait too long before finding out. The new Pokemon will evolve again just three levels later, so obtaining Beautifly and Dustox isn't actually that difficult, although it may require a few attempts.
Wurmple Evolutions
- Wurmple -> Silcoon: Reach level 7 with a specific Personality Value.
- Wurmple -> Cascoon: Reach level 7 with a specific Personality Value.
3 Slowpoke
When it comes to Pokemon evolutionary lines that have grown in complexity over the years, few can rival Slowpoke's. In Gen 1, it simply evolved into a Slowbro when it reached level 37. The introduction of Slowking in Gen 2 changed things up a little though, with players now able to trade their Slowbro while holding a King's Rock to instead obtain this new, slightly superior form.
Upon their arrival in Galar, however, players were greeted with a Galarian form of Slowpoke; which in turn meant Galarian forms of each of its possible evolutions. Rather than evolving via the same methods, however, players instead need to use one of two newly added consumable items in order to trigger the change. Using a Galarica Cuff on a Galarian Slowpoke will cause it to evolve into Galarian Slowbro while using a Galarica Wreath will instead lead to it becoming a Galarian Slowking.
Slowpoke Evolutions
- Slowpoke -> Slowbro: Reach level 37.
- Slowpoke -> Slowking: Trade Slowpoke while it's holding a King's Rock.
2 Burmy
There may only be two stages to Burmy's evolutionary line, but it's able to evolve into any one of four unique forms depending on a few different variables. The first of these is the Pokemon's gender whilst the second is its cloak; the latter of which changes regularly to reflect the last area in which the Pokemon battled.
If the Burmy is male, it will always evolve into a Mothim at level 20. If it's female, however, its second stage form and secondary typing will depend on the Burmy's cloak at the point when it hits level 20. The resulting Pokemon, Wormadam, will always be a bug-type Pokemon, but its secondary type will be grass if it evolves with its plant cloak, ground if it evolves with its sandy cloak, and steel if it evolves with its trash cloak.
Burmy Evolutions
Burmy -> Wormadam (Plant Cloak): Reach level 20 with a female Burmy after battling outside or in tall grass.
Burmy -> Wormadam (Sandy Cloak): Reach level 20 with a female Burmy after battling in a cave or on a beach.
Burmy -> Wormadam (Trash Cloak): Reach level 20 with a female Burmy after battling in a building.
Burmy -> Mothim: Reach level 20 with a male Burmy.
1 Eevee
When it comes to complicated evolutionary lines, Eevee has always been ahead of the curve. Its three distinct evolutions found in the very first Pokemon games were incredibly simple though when compared to the Pokemon's most up-to-date evolutionary tree.
There are currently eight unique Pokemon that an Eevee can evolve into, with Espeon, Umbreon, Leafeon, Glaceon, and Sylveon all joining Vaporeon, Jolteon, and Flareon in the years that followed Gen 1. Five of these forms require the use of an elemental evolution stone while the others instead rely on things like affection and friendship stats and the time of day that the evolution takes place.
Eevee Evolutions
- Eevee -> Vaporeon: Use a Water Stone on Eevee.
- Eevee -> Jolteon: Use a Thunder Stone on Eevee.
- Eevee -> Flareon: Use a Fire Stone on Eevee.
- Eevee -> Espeon: Level up with a high Friendship stat during the daytime.
- Eevee -> Umbreon: Level up with a high Friendship stat during the nighttime.
- Eevee -> Leafeon: Use a Leaf Stone on Eevee.
- Eevee -> Glaceon: Use an Ice Stone on Eevee.
- Eevee -> Sylveon: Level up with a high Friendship stat after learning at least one fairy-type move.