Many Pokemon are based off of animals, objects and myths. However, the myths these Pokemon are inspired from are kind of creepy.
Misdreavus is a mischievous ghost-type Pokemon with no visible extremities. It basically looks like a floating head with a dress. This Pokemon is based off of a Japanese mythological creature called a nukekubi. Nukekubi are female humanoid creatures with heads that detach from their bodies and freely fly around at night. It's said that during the night, they wail and scream to increase fright.
Sneasel is based off a creature known as a kamaitachi. Kamaitachi are weasel-like monsters with sickles for hands. According to the mythology, kamaitachi hunt humans in packs of three, each having their own job. One is in charge of knocking you down, another one cuts flesh off the human's leg and the last one sows the leg up so it's like nothing ever happened. It happens so quickly that you don't even realize you've been attacked. You're simply just left thinking you tripped.
Fox spirits are one of the more commonly known type of spirits in Japanese folklore. These spirits are said to grow extra tails every 100 years until they reach nine. When a fox spirit achieves nine tails, they become god-like with infinite wisdom and power. Their fur also shifts from red to white. Insert obligatory Naruto reference here.
Jynx is both a reference to the Japanese fashion trend known as ganguro and witch-like monsters called yamanba. Yamanba live like hermits in the icy mountains and like sirens, they lure lost travelers to their cabin where they would proceed to eat them.
Espeon comes from a creature called a bakeneko. Like the name suggests, bakeneko is a "changed cat". Like Espeon, bakeneko have split tails. In mythology, these shapeshifters are known to speak words, transform into humans, curse humans, possess humans, manipulate the dead, and join wolves to attack humans.
Zapdos, one of the three original legendary Pokemon, is based off a Native American mythological creature called a thunderbird. A thunderbird is a supernatural bird with powerful, enormous wings, capable of producing thunder with each flap. In mythology, this bird is the spirit of lightning, thunder and rain.
A myth of a strange paranormal encounter in Kentucky was the inspiration for Sableyes. Sometime in 1955, bizarre sightings of gremlin-like aliens were being reported at a local farmhouse. It was said that their arms and legs looked atrophied and they moved in a erratic swaying motion. It's also said that bullets would bounce off their bodies.
Mawile is based on a story about a futakuchi-onna, a woman with a second mouth hidden on the back of her head. As the legend goes, a poor farmer married a woman who ate next to nothing. He was greatly pleased with his wife because it hardly costed anything to keep her fed. As time went on, the farmer noticed that his supply of grains were mysteriously disappearing. One night the farmer awoke from his sleep, when he looked over to his sleeping wife and was horrified to see a second mouth on his wife's head. The woman's hair acted like tendrils, picking up rice and feeding the second mouth non-stop. The futakuchi-onna literally ate him out of house and home.
Whiscash's inspiration comes from a legend created during the Edo period in Japan. It was believed that catfish were much more active right before an earthquake, from this a myth began spreading about Onamazu, a giant catfish who was able to cause earthquakes. This goes hand and hand with Whiscash's Pokedex description, "it thrashes about and triggers a massive earthquake." It also explains it's water and ground typing.
Coming from a Chinese legend, Absol is a reference to Bai Ze, a beast with the power of foresight and knowledge of the supernatural world. It's said that Bai Ze taught the Yellow Emperor Huang Di about the supernatural world and how to defeat it's inhabitants. When the myth crossed over to Japan, the beast's name was changed to Kutabe and was said to come out of the forest to warn humans of upcoming disasters.
During the 16th century, the Czech Republic government would terrorize the Jewish civilians of Prague with anti-Semitic attacks and sanctioned massacres. It was said that during this time, a Rabbi called upon God to bring life to a clay sculpture. The sentient golem would then protect the city's inhabitants. This fabled golem was the inspiration for Golurk. Gorlurk also borrows many of the golem's aesthetics, like the crack in the chest.
Frosslass original concept derives from the Japanese myth of the Yuki-onna. The Yuki-onna is a beautiful ghostly woman in a white kimono who would hover over the snow. If the Yuki-onna ever targeted you, she would kill you with cold. A few of the ways she would do this is she would lead you away from your home until you died from exposure, knock down your doors exposing your home to the elements or she would just directly freeze you on the spot.
Xerneas, Yvetal, and Zygardesynchromiss
Xerneas, Yvetal and Zygarde each come from Norse mythology. Just like their counter parts, Xerneas is an almighty stag, Yvetal is a giant eagle like bird, and Zygarde is a snake-like dragon.
Groudon, Kyogre and Rayquazasubsequent
Believe it or not, but Groudon, Kyogre and Rayquaza are based off of mythological monsters from the Bible. The Old Testament mentions a Behemoth, Leviathan and Ziz, creatures so big that they represent the very forces of nature. Groudon represents Behemoth, Kyogre (whale in modern Hebrew) represents Leviathan and Rayquasa represents Ziz.
Dunsparce comes from a very strange looking mythical creature. It's said that there is a peculiar looking snake called a tsuchinoko (a.k.a bee snake) that lives in Japan. This snake has a stubby body, a poisonous stinger for a tail and can leap through the air.
Drowzee and Hypnohyakumonogatari
There's a reason why Drowzee and Hypno look so weird, it's because they're based on the Baku spirit. Baku are thought to be a hodgepodge of random, leftover pieces after God finished creating all the animals. These tapir-like creatures would roam around and eat people's dreams.
Dusclops are based on chochin-obake (lantern spook). These spooks look like normal lanterns, however they have one eye and a protruding tongue.
It's probably no surprise that Manetric is based on a lightning wolf called Raiju. Raiju is the pet of the Shinto thunder god. Here's a random piece of information, it's said the Raiju would often like to hide in people's belly buttons.