Over the course of 15 seasons, Supernatural, starring Jensen Ackles and Jared Padalecki amassed an eclectic array of wonderfully weird creatures - or unusual takes on classic monsters. While some are almost direct translations of folklore to screen, other times, the show has taken an alternative approach to some of these traditional creatures and monsters.
Sam and Dean have hunted beings from vampires to God himself and have killed an innumerable number of monsters - whether these creatures were at times the big bad of a whole season or were just another monster-of-the-week hunt for the brothers.
Jefferson Starships
Jefferson Starships were a scary kind of weird. These creatures were created by Eve - mother of all monsters - in retaliation to Crowley's killing and torturing of her children. They took on various traits of vampires, shapeshifters, and wraiths. And as part of a hilarious running joke throughout Supernatural, they were named by Dean because Jefferson Starships are "horrible and hard to kill."
Eve's "beta-testing" for "building the perfect beast" took a few tries and a lot of dead bodies to get it right. But once Eve perfected her formula, they were surprisingly terrifying and powerful creatures. While weird, if it wasn't for Dean killing Eve and Castiel smiting the Jefferson Starships, they most likely could have destroyed or turned the human population, just like Eve wanted.
Musca
Completely different from the monsters from the earlier seasons of the show, the Musca from season 14 of Supernatural is a human fly hybrid similar to that of Jeff Goldblum in his 1986 film The Fly. These creatures are most definitely strange, and the cause for a hunter's case in the show is a "bad egg" who leaves his nest as they're mate-less and nests on human beings bound together by a goo the Musca secretes.
While lore suggested that a brass nail dipped in sugar water will kill it, modern methods of bullets and blades seemed to work just as well when Sam and Apocalypse-verse Charlie killed the creature. This "giant fly with low self-esteem" is definitely one of the weirdest monsters in Supernatural.
Shojo
A shojo or shōjō is a Japanese sea spirit with a fondness for alcohol. In folklore, they appear as creatures with red faces and hair; however, Supernatural's interpretation of the creature shows a pale young woman with long dark hair similar to Sadako/Samara from the Ring franchise.
Though their frightening appearance, which includes claws, and powers of invisibility, strength, and telekinesis make them formidable opponents, the best and weirdest feature of a shojo is that one can only see them when intoxicated. Though incredibly powerful, Dean is able to kill the shojo with a katana consecrated with a Shinto blessing. Appearing in only season 7's 'Party On, Garth,' this creature is memorable to all fans as no one had quite seen the Winchesters (and Garth) as intoxicated as they had to be so they could fight this monster.
Pishtaco
Pishtaco is a parasitic creature from Peru that feeds on the fat of humans. They only appear in season 9's 'The Purge,' which features the first appearance of fan-favorite and low-key hero Donna Hanscum. Not only is this creature weird, but it is also an underrated monster with a fascinating history.
Folklore shows this creature as the boogeyman of the Andes region in South America, particularly Peru and Bolivia. While they also suck the fat out of their victims, tales show them to be far more terrifying and violent. Pishtacos are unquestionably one of the most terrifyingly unusual monsters to have appeared on the show.
Bisaan
Though nicknamed the Chitters for the noise they produce, the Bisaan are cicada spirits that originated in the forests of Malaysia. The Bisaan, while slightly terrifying, are rather weird creatures with bright-green eyes and fangs, and the Bisaan, like most monsters in Supernatural, possess humans.
In folklore, the Bisaan are female nature spirits who can appear in the form of a cicada that protects camphor-bearing trees. While they are easily jealous, they seem more-or-less harmless. Unlike the folklore, Supernatural's interpretation of these creatures are malevolent and use humans to breed - which spouts all sorts of rumors in town about the spring equinox creating unparalleled lust.
Fairies
Season 6 brought a variety of unusual creatures to the forefront, including fairies. It turns out fairy realms, like Oz and Avalon, exist and that fairies like to take people in a similar manner to alien abduction. In the varied assortment of fairy creatures, Elves, Red Caps, Leprechauns, and flying monkeys are also real. As Supernatural postulated over many years, nothing is truly out of the question when it comes to monsters.
Technically first appearing in season 3's 'The Kids Are Alright' with fairy-adjacent creatures such as changelings, they are not revealed as real until the hilarious episode of 'Clap Your Hands If You Believe...' After this point, they continue to pop in from their realms throughout the seasons and even provide adventures for fan-favorite character Charlie for a while.
Dragons
Eve, in an attempt to get even with Crowley, brought back a lot of old favorite monsters and creatures, including dragons. Even Sam, Dean, and Bobby have a hard time believing that - and they'd met Satan. Supernatural's version of such a beloved creature is unlike traditional dragons in almost every way.
While still apparently able to change into a large reptilian creature, these dragons mostly take the form of humans who still possess powers of pyrokinesis. As most legends go, dragons are notoriously hard to kill, which remains the same for Supernatural when Dean has to hunt down a sword forged in dragon blood in order to kill the dragons. These creatures and the entire episode gave way for hilarious one-liners about World of Warcraft, Harry Potter, and Middle-earth.
Kitsune
While the folklore surrounding Kitsune is vast and largely not agreed upon, Supernatural's take on the Japanese creature is definitely weird. In folklore, Kitsunes are ancient fox spirits that possess supernatural abilities - some Kitsune are peaceful, while some of these supernatural beings are wrathful and powerful, as explored in MTV's Teen Wolf.
Unlike traditional Kitsune in most ways, Supernatural's monsters appear human apart from their fox-like claws and eyes they use to attack. Also unusually, these creatures specifically must feed on the pituitary glands (a pea-sized gland at the base of the brain) to survive. The translation of Kitsune from folklore to season 7's 'The Girl Next Door,' while odd, is fascinating.
Zanna
From Romanian folklore, Zanna or Zână is equivalent to a fairy godmother who appear to children as "imaginary friends." Based on children's inspiration, naturally, Zanna are fairly weird creatures, and though they only appear in one episode, Sam's former Zanna, Sully, quickly became a fan-favorite.
As most children are extremely creative, the Zanna go to incredible lengths with their transformations - including appearing as a mermaid or a half-human half-unicorn hybrid. Or as Dean coined it, "a manicorn". Apart from their interesting appearances, they also have powers of teleportation, invisibility, and telepathy with other Zanna. It is fortunate they are so benevolent; otherwise, they could have been a powerful force of evil.
Leviathans
As the main villain of season 7, the Leviathans were frightening creatures that even God (or Chuck, if one would prefer) himself didn't want to deal with them. Locked away in Purgatory for millennia saw them return with a fiery vengeance to harvest and eat all of humankind. While scary, they are unusual monsters.
Supernatural's Leviathans are drastically different from Judeo-Christian tradition, which regards these creatures as giant sea serpents. Instead, these monsters appear human, except for when they show off their sharp teeth and bifurcated tongue in their expanding jaw that is as big as a human head. Bleeding black goo with weaknesses such as blood of the fallen and sodium borate found in cleaning products, the Leviathans are a weird but effective choice for villains.