Found in the Kanto region, the first generation of Pokémon introduced the world to 150, later 151 with the inclusion of Mew, unique pocket monsters. Fans everywhere fell in love with these characters and it made the franchise a huge success, one that is still going strong over 20 years later.
While many of the original Pokémon feature iconic designs, names, and powers, not all of them actually make sense. A turtle-like Pokémon that squirts water makes sense, but some combinations of design and power or type are far less intuitive. Additionally, some Pokémon have unclear designs, inconsistent evolutions, or confusing powers.
Metapod
For many trainers, Caterpie is one of the first Pokémon that they catch given that Caterpie is fairly common and relatively easy to catch. While Caterpie is not especially strong, it does evolve starting at level 7. However, after putting in the work to evolve their Caterpie, trainers are left with the essentially useless Metapod.
On its own, Metapod can only develop the move Harden, which has no attack value. While it does eventually evolve into Butterfree, Metapod is basically useless until then and just feels like a means to an end.
Diglett
Many Pokémon are based on real-world animals or objects. Diglett, however, is a little brown Ground Pokémon whose appearance is a mystery. When Diglett pops up from underground, only its head is visible.
In the game Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team, it is mentioned that Diglett has feet, though they are never seen. Diglett's appearance makes no sense as it is unclear what it actually looks like. Even the aspects of Diglett that are visible make no sense as its head appears to just have eyes and a nose.
Psyduck
Appearing as a duck, Psyduck is a Water-type Pokémon that often has an immobilizing headache from psychic energy. Because of this, Psyduck often ends up injuring itself with Confusion.
There is no clear reason a duck-like Pokémon would possess psychic powers but it makes even less sense that Psyduck not only has psychic powers but also cannot control them and is basically rendered useless because of them. Many of these issues are sorted out when Psyduck evolves into Golduck, whose powers are more focused on Water-type moves than Psychic ones.
Poliwrath
Poliwag is a small, tadpole-like Water Pokémon that evolves into Poliwhirl, a larger Water Pokémon that resembles a blue frog with a swirl design on its torso. The final evolution, Poliwrath, looks very similar to Poliwhirl but suddenly moves from being Water-type to dual Water/Fighting-type.
It does not make sense that exposing Poliwhirl, a Water Pokémon, to a Water Stone would suddenly turn it into a dual-type. This problem was later compounded by the addition of Politoed as a possible evolution. Politoed is a Water-type that evolves with a King Stone. It makes no sense that the Water Stone turns a Water Pokémon into a dual-type and a King Stone is needed to evolve a Water-type into a Water-type.
Golem
The evolution from Geodude to Graveler is a natural one as what is essentially a rock with arms grows into a boulder with arms and legs. The two look very similar and clearly appear related to one another. This all changes, however, when Graveler evolves into Golem.
Unlike Geodude and Graveler, Golem is not simply an anthropomorphic rock but is instead a tortoise-like Pokémon that uses a boulder like a shell. Golem has a cool design, but it simply does not fit with the other Pokémon in its evolution set. It makes no sense that Graveler suddenly becomes a tortoise-like Pokémon when it evolves into Golem.
Seel
Seel is an adorable if lazily named, seal-like Water Pokémon that lives in arctic waters, using its horn and tusks to bore through the ice. Because of this, it would make sense for Seel to be a dual Water/Ice-type Pokémon.
When Seel evolves into Dewgong, it keeps much of the same look. Dewgong lives in the same conditions as Seel and also uses its horn to cut through the ice. Essentially, Dewgong is similar to Seel in every way but one. Unlike Seel, Dewgong is a dual Water/Ice-type. It makes no sense that Seel is not also an Ice type.
Shellder
Shellder is a clam-like Water Pokémon that evolves into Cloyster, a dual Water/Ice-type through the use of a Water Stone. Several of Shellder's best attacks are Ice-type and its evolution is a dual-type, so it makes no sense that Shellder is not also a dual Water/Ice-type.
Additionally, it does not make sense that Shellder's shell completely changes shape and color when it fuses with a Slowpoke to form a Slowbro or Slowking. It would make much more sense if Shellder either retained its shape or at least looked more like Cloyster when it attached itself to Slowpoke.
Marowak
Cubone has perhaps the saddest backstory of any Pokémon. Most of Cubone's face is unseen as it wears its dead mother's skull. This dinosaur-like Pokémon is timid and shy as it continues to grieve.
But as Cubone evolves into Marowak, its personality and appearance change, growing into a confident and aggressive Pokémon. Marowak still wears the skull but it is now part of its own head. Most of the changes make sense as Marowak retains many similar aspects of Cubone's appearance and character. However, it makes no sense that the skull would be able to completely change in shape and appearance.
Staryu
With five appendages, Staryu resembles a starfish, but at its center is a gem-like core that can reveal its energy. In the wild, Staryu has been known to flicker its core in conjunction with the stars at night, displaying some kind of connection with the night sky.
Because of this unexplained behavior, it does make sense that Staryu's evolution, Starmie is a dual Water/Psychic-type. Given the odd celestial connection and the fact that its evolution is a dual-type, it makes no sense that Staryu is not also a dual Water/Psychic-type.
Magikarp
Magikarp, the carp-like Pokémon, is considered one of the weakest generation 1 Pokémon. Until it reaches level 15, the only move that Magikarp learns is Splash, a move that has no effect. In order to level up Magikarp, trainers are either forced to feed it Rare Candy or swap it in and out of battles to gain experience.
However, once Magikarp evolves, it turns into Gyarados, one of the coolest and most powerful generation 1 Pokémon. Magikarp does not resemble Gyarados in appearance, power, or type. it makes no sense that Magikarp has nothing in common with its next evolutionary stage.