Evil is seductive, and to drive that point home, bad guys can be Lean and Mean, elegant, creepy, or sexy. Some bad guys even combine those traits in different combinations, giving you creepy-sexy bad guys as just one example.
To further underline the seductiveness and underscore the temptation of evil, some Evil characters also seem to share a certain kinetic trait: body language that implies a certain gravity-defying elegant grace, a boneless, flowing, fluid manner of movement. It can be sexily alluring, or unnervingly disturbing, but serves as a visual cue to a viewer that a character who moves in this manner is sliding away or completely removed from what we consider "their humanity", and as such is not a sympathetic character to root for.
In more supernatural cases, the villain does literally and voluntarily shift from solid to liquid or gas at will. Villains who are animals can display this trait honestly as it will often be a species trait: eels, reptiles (especially snakes), weasels, cats and rats all slink. Occasionally, due to them not being able to help how they move — and bad reputation — you may encounter slinky animals who are neutral or good despite what it may look like when they move.
One of the oldest temptation villains, the serpent in the Garden of Eden, exhibits the same motion.
Characters who exhibit this manner of movement are almost always evil. Usually, if a good character is moving in an inhuman manner, it's usually more rubbery than slinky-liquid.
The trope is most commonly applied in animated fare, but it does make appearances in live action as well.
- One Piece:
- Trebol, a member of the Donquixote Pirates, is a living nitrocellulose-man who moves around like a blob and has No Sense of Personal Space.
- Another from the same group, Senor Pink, is able to "swim" on hard surfaces such as stone floors or walls.
- Diamante of the same group is able to turn himself, or anything he touches, into fluttering like a flag. He not only moves swiftly with his "flat" form, but he also attacks swiftly and confusingly by turning his long sword into a Whip Sword.
- Boa sisters Sandersonia and Marigold both can turn into snakes, but Sonia is slinkier since she moves much faster and is able to evade lots of attacks at once, while Mari takes a slower and defensive approach.
- One of the first antagonists encountered by Plucky Girl Leina from Queen's Blade is Melona, a demon-girl in service to the Swamp Witch. She's composed of pink goo, so swords have no meaningful effect on her, and she can escape capture by liquefying herself and draining away like water.
- Disney is fond of this trope, in its franchise form or while working with Pixar.
- Aladdin: Jafar worked the slink, and in the climax of the first film, took it all the way to transforming into an actual serpent.
- The Great Mouse Detective: Ratigan is an actual rat.
- Hercules: Hades glides effortlessly on Fog Feet.
- Lady and the Tramp: The Siamese cat twins worked the slink◊ as only a pair of feline douchebags can.
- The Little Mermaid (1989): Ursula the sea witch slunk like a pro on her octopus-like tentacles, even using her cave walls to really push the creepy and menacing effect. Flotsam & Jetsam are eels, coming by the slink naturally.
- Monsters, Inc. but not Monsters University. Randall Boggs was a decent guy for most of the prequel and hadn't really developed the slinky way of moving until the events of the first film.
- The Princess and the Frog: Dr. Facilier and his "friends on the other side". Justified in their case, as they were literally nonhuman and granted some of that to their charge until he lost their good will.
- Sleeping Beauty: Maleficent had a more regal, gliding way about her, but still slinky.
- Treasure Planet: Inverted. Morph moves like liquid but is good.
- The Lion King (1994): Scar is a big cat, thus this is somewhat inevitable, but his motions are much more slinky compared to the good lion characters who are brawnier and walk more elegantly.
- The Jungle Book (1967) has the sneaky, hypnotic snake Kaa and the vicious tiger Shere Khan as the two main antagonists. The first one appears in two scenes where the animators clearly had a lot of fun animating his slithering motions, and the other is introduced in a scene where he crawls through tall grass to stalk a deer.
- In The Book of Life, both death gods move slinkily, but cheating, sneaky Xibalba more than kind-natured La Muerte.
- In Cloudy with a Chance of Meatballs 2, Chester is briefly seen spying on Flint and his friends, slinking on a branch like a python.
- FernGully: The Last Rainforest: Hexxus was literally non solid. He was oily sludge, and smoke, and moved like it.
- Rock & Rule: Mok moves in that boneless, slinky way...and so did whatever it was he summoned with Angel's voice.
- Sinbad: Legend of the Seven Seas:
- Eris used the slink to disturbing effect, randomly growing her face and body out of her constantly writhing mass of hair.
- The Sirens also slink, by dint of being made of water.
- The villain Barnaby, played by Ray Bolger, from the Disney version of Babes in Toyland, especially during the song "Castle In Spain".
- Gary Oldman starring as the titular Bram Stoker's Dracula tended to move slinkily at night when his powers were at their peak. His shadow also slunk — separately and independently of him.
- In both the original Clash of the Titans and the 2010 remake, Medusa is part snake and slinks evilly.
- Who Framed Roger Rabbit:
- Jessica Rabbit is not bad, she's just drawn (and moves) that way.
- Judge Doom's Weasel Boys.
- The Frighteners: The Big Bad that plagued Frank and the town for most of the movie looked humanoid most of the time but could slink its way through cracks and crevasses at will.
- Harry Potter:
- The Hogwarts house of ambitious wizards (though it is also notorious for producing evil ones such as Voldemort) is called Slytherin. Pronounced "slither in," it invokes the trope. Its symbol is a snake.
- Alan Rickman pulls it off in live action as Snape, even though he's a Red Herring. The true villain, Voldemort, is supposed to be reptilian, but isn't nearly as slinky.
- The Film of the Book The Phantom Tollbooth: the denizens of the Doldrums were all gooey blobs of liquid sludge.
- Rise of the Guardians: shadowy bad guy Pitch Black.
- Terminator 2: Judgment Day: The T-1000 was made of liquid metal, and flowed from one form to another until it was too badly damaged to do so smoothly anymore.
- In both West of Zanzibar and its remake Kongo, the protagonist (Lon Chaney in the original, Walter Huston in the remake) is an Evil Cripple who is paralyzed from the waist down. Sometimes he uses a wheelchair, but at other times he slithers around like a snake.
- The Jungle Book (2016) plays with the trope - unlike his animated counterpart, this Shere Khan is no more slinky than is inherent in being a tiger and considerably less than the smaller, lither Bagheera. Kaa, on the other hand, is as slinky as can be (being a snake makes this somewhat inevitable.)
- It (2017) features Pennywise the Dancing Clown, who when not standing still to loom ominously or rushing victims in a feral charge, favours slinking his way up to them in a way that complements his theatrical appearance.
- Depending on which myth you read:
- Medusa slinks like a snake and is evil because she's enraged about her punishment for sleeping with Poseidon in Athena's temple. Or in a different version she claimed to rival Athena in beauty. Or possibly just because she and her equally-monstrous sisters were born to primordial sea-monster-gods.
- Or she slinks like a snake and is not evil because she's grateful to Athena for making it so men cannot touch her against her will ever again after seeing her loyal priestess get raped by Poseidon despite being in the "safety" of Athena's own temple. This fairly modern/recent interpretation is also a case of Sadly Mythtaken, as Athena transforming Medusa is more traditionally depicted as a victim-blaming hissy fit on Athena's part (read: She wasn't showing Medusa mercy in any of the Roman versions of this myth; she transformed her as a punishment for being raped).
- Quetzalcoatl is a winged snake that slinks and flies. It is a god-creature, so it may be more ineffable than evil.
- Ouroboros is a snake that does not slink as it is perpetually eating its own tail.
- Some Japanese stories describe the Yuki-onna as moving like this.
- That snake in The Bible slunk down out of the tree to tempt Adam and Eve. In some versions of the story, it had legs and could walk, and God cursed it to crawl forever on its belly for tempting his humans to disobey.
- The Assassins' Guild of the Discworld aren't exactly evil but have an image that involves intentionally living up to Evil Is Cool. The standard Assassin method of locomotion is "slurking", which is a Portmanteau of slinking and lurking.
- In the works of J. R. R. Tolkien:
- Gollum from The Lord of the Rings originally looked like a hobbit, but the Ring's corruption turned him into a hideous mutant who crawls around on all fours. Sam even gives him the nickname "Slinker". Credit must go to mocap actor Andy Serkis for the on-screen slinkage in The Movie of the Book.
- Smaug from The Hobbit also moves in a slinky, reptilian way, due to being a dragon with a serpentine body. According to Word of God, his name comes from the primitive Germanic word smúgan, meaning "to squeeze through a hole" (Gollum's other name, Sméagol, derives from the same word). Just as in Gollum's case, in The Movie of the Book (specifically The Hobbit: The Desolation of Smaug), actor Benedict Cumberbatch had to crawl on all fours to create the motion capture reference.
- Many villains in The Dresden Files, especially White Court Vampires, move like this. Understandable for the White Court as they are seductive creatures that feed on lust, so they'll try to seduce just about anyone they come across.
- Buffy the Vampire Slayer: Slick, who caused Sunnyvale to turn musical was a literal dancing demon, and could slink even while standing still. A dancer was cast to play him.
- Sesame Street: There's one of the shorts from an earlier season about a snake called Sammy the Snake — who averts the trope because although he's a snake Muppet, he's not evil. He is an intentional aversion of the trope because Sesame Street goes to effort to portray things usually considered scary to children as friendly and approachable.
I'm Sammy the Snake and I look like the letter S — oh yes.
I'm all wiggly and curvy. I look like the letter S — I confess.
But do you know the sound of Sammy the snake?
The sound of the letter S is the sound that I make.
I say "Sssss" in the morning.
"Ssss" in the afternoon — yes I do, to all my snake friends
I say "See ya later, Slinky" ... she's my sister.
I say "See ya soon." Yeah, she's super slick...
- Sleepy Hollow: Several of the monsters in this series do the slinky thing.
- There was a smoke demon who hopped from body to body on a wisp of smoke.
- There was a water demon who slinked out of puddles and yanked people into them to drown.
- CSI cast world-class contortionist Daniel Browning Smith to portray Sqweegel, a latex-bodysuited killer who alternates between snaky slinking and lizard- or spider-like scuttling.
- Good Omens (2019): Demon Crowley's alternative form is a snake, and he walks in a way that reflects this. It straddles the line between Sexy Walk and Silly Walk.
- In Evolve, the Wraith slinks and slithers as it moves by virtue of its anatomy.
- In the Mr. Magoo animated feature 1001 Arabian Nights, the Evil Vizier slithers like a snake when sneaking into Magoo's house.
- Avatar: The Last Airbender: The dragons in the Avatar-verse are generally good but get the slink honestly because they're reptiles.
- In "The Earth King", in Zuko's fever dream, however, the dragon with Azula's voice was evil and slinked accordingly.
- The titular Grinch in the Chuck Jones animated How the Grinch Stole Christmas! slunk along the ground like a snake during the sequence in which he robbed Whoville.
- The Legend of Korra:
- The spirit Vaatu was all evil, all slink. Raava, who was not evil, tended to float and glide.
- Zuko's dragon has the "is a reptile" version of the slink but is not evil.
- My Little Pony: Friendship Is Magic: Discord is the most slinky of the villains on the show. Justified in that the hodgepodge of body parts that make him up includes dragon.
- The Powerpuff Girls: villain Him exhibited the snake-like slink on multiple occasions.
- The Simpsons
- The Simpson family are forced by circumstances of the plot to steal all the Funzo toys that everyone has bought for their kids for Christmas, so Bart & Lisa distract the household by singing Christmas carols while Homer sneaks in Grinch-like, and at one point slithers around as the Grinch does.
- In the Harry Potter spoof, Smithers plays Voldemort's snake and is now called "Slithers".
- Steven Universe:
- Lapis Lazuli's clothes tend to flow around a lot like her water. She's not all bad, but it does make her look more intimidating.
- The episode "Reformed" features Garnet, Amethyst, and Steven featuring a corrupted gem that moves so slinkily that Steven's nickname for it, "The Slinker," sticks. The slinker is rather ferocious and has no compunction against killing gems.