Evil-Detecting Dog

"I’m suspicious of people who don’t like dogs, but I trust a dog when it doesn’t like a person."

- @BiIIMurray

Unlike humans, animals seem to have an inherent ability to detect a malicious character even if it's not obvious to anyone else. May not apply to pets of a villain, although attack dogs and Bond-style cats have a surprisingly low sense of loyalty in a pinch.

This doesn't always count in a comedic situation; snotty pets frequently hate everybody, and will be nasty to characters who likewise dislike them.

A character's dog reacting oddly to their presence is often the first sign that character's been replaced by an Evil Twin. Or just an ordinary twin. This is not actually implausible, unless the scent of the replacement for some reason is exactly the same as the replaced person. Heart rate and other things might reasonably be detectable to some animals, too.

If the animals know something's coming, sometimes they don't run, they go quiet. In fact, too quiet...

This trope is not restricted to dogs—cats and horses are also commonly invoked, amongst other creatures. Nor necessarily animals—some plants have the ability too. When a human character has this power, it's a Gut Feeling.

Not to be confused with Even the Dog Is Ashamed.

If the dog can detect the supernatural, it's because of a Glamour Failure.

Contrast Licked by the Dog, where this is used to show the audience a good guy instead of a villain. Then again, sometimes they aren't detecting evil at all, and it's simply that Animals Hate Him.

Contrast They Have the Scent.

If the dog is attempting to warn its master or another nearby human character but the warning is dismissed (typically due to annoyance at the dog's repeated barking or other unusual actions), it can be a form of Not Now, Kiddo. Animals can also detect especially good people, if they're a Friend to All Living Things.

Anime and Manga

 * Not evil, but in Tokyo Mew Mew, dogs can sense that Ichigo is a catgirl even when she's in the form of a human, and start barking at her for no reason. With her Lancer Minto and her boyfriend Masaya both owning dogs, this becomes a problem.
 * A cat detects Sylvie as a boomer in episode 6 of Bubblegum Crisis.
 * Kicchomu in Thriller Restaurant has an uncanny skill in detecting evil spirits and doppelgangers. This is exhibited in episodes 6 and 14.
 * In Saber Rider and the Star Sheriffs there's the Scottish terrier that belonged to Saber Rider's parents. When they were kidnapped and impersonated by Vapor Beings in "The Highlanders", he barked and hissed at them, which weirded Saber out since he was very sweet to them...
 * Maru-chan is initially terrified of Sawako in Kimi ni Todoke. This is a subversion, however, since Sawako only looks creepy and is actually one of the kindest people you could hope to meet.
 * In Fullmetal Alchemist, the Big Bad starting to move around usually coincides with every dog in Central going insane. Not only can animals sense the homonculi and, but even the gentle dog Den reacted viciously to one to show the inherent wrongness of what they are. Not only that, when the Big Bad exerts his power enough, he can make every single animal in the city go crazy and bark at the earth, not just the dogs. The Big Bad himself makes animals too afraid to even approach his lair.
 * Special mention should also go to Black Hayate, Riza Hawkeye's dog, who not only can sense the Homunculi but viciously attacked one to save his beloved mistress. Roy Mustang awarded him the honorary rank of Second Lieutenant for his services to their cause.
 * Kiba's dog, Akamaru, from Naruto is able to sense just how strong a chakra is in a person. When he starts whimpering, that means trouble close by.
 * In the third volume for Axis Powers Hetalia, young Lithuania has a dog with him that starts barking wildly when it sees young Russia. Also notable in that Russia wasn't evil at the time, so the dog was apparently precognitive too.
 * The Jinnouchi family dog in Summer Wars is so good at detecting evil that it can sense.
 * He's pretty skilled at detecting good as well, if his reactions towards a certain Jerk with a Heart of Gold are anything to go by.
 * The two ghost dogs of Kekkaishi are primarily used to detect other evil spirits or people.
 * In Wild Rose, Tranquilo immediately starts growling when he detects the rogue manbeast's presence and tries to protect Camille from him, getting badly injured in the attempt. In contrast, Tranquilo's immediate acceptance of Kiri shows that he's safe.
 * The Hentai Alien from the Darkness has Einstein, a ferret who growls and hisses whenever alien-possessed Flair is nearby.
 * In Princess Mononoke, San and her wolf companion find hundreds of mice scurrying away from the direction where humans using boar skins to masquerade themselves to find the Forest Spirit. Apparently they're so terrifying that they willingly scurry over a full grown woman and a giant wolf to get away.
 * In episode 15 of Tiger and Bunny Keith Goodman's dog, John, growls at and tries to keep Keith away from the pretty girl on the park bench. The reason being that while Cis looks like a nice lady,
 * Hotarubi from Basilisk has a pet viper that could see through Kisaragi Saemon's disguise. Unfortunately, Hotarubi didn't understand the meaning of her snake biting her lover and just tossed the animal away and sucked the poison out of Saemon's finger by herself!

Comic Books

 * When Impulse Bart Allen was replaced by his Evil Twin Inertia, the only character to realize was Bart's dog, but Inertia was able to get around that with treats. And by not thinking any evil thoughts around the dog.
 * In Supreme Power, his foster parents give the alien baby Hyperion (a modern version of Superman) a puppy for his first birthday. It immediately senses, that he is not human, and tries to attack him. He promptly (and instinctively) annihilates it with his heat vision.
 * Wookiees are explicitly sentient, but since they're hairy and unintelligible, unimaginative writers of books and comics alike love to make them as animalistic as possible. This is taken to a new height(or low) in one arc of the X Wing Series - a woman who has a Wookiee hanging around due to a life-debt doesn't understand him, and he doesn't communicate with her at all, he's just a bodyguard - who starts growling and provoking "Groznik senses something!" before they get attacked.
 * One Far Side comic strip had a dog preparing to growl at an empty closet, just to mess with his human owner's head.
 * In Zombies: A Record of the Year of Infection the main character writing an Apocalyptic Log notes that dogs go nuts at the presence of zombies, including frequently attacking them. Furthermore.
 * The demons in Chick Tracts are invisible to all the characters...except for Fang, a (badly drawn) dog who occasionally barks at them in the background.
 * In the mid-90s Robocop vs. Terminator comic book, one of the humans remarks on the fact that a dog acts friendly, rather than hostile, to Robocop, proving to the human that said character couldn't be a Terminator.

Fan Works

 * The cats are used for this in Aeon Entelechy Evangelion, as they are sensitive to anything abnormal, a quality shared only by human infants, and thus are also used in CATEYES security systems. This also seems to be common knowledge since Shinji notes their absence in the dome where Rei lives.
 * In The Dilgar War dogs are the only thing that can locate the Spectre, Dilgar special forces equipped with cloaking suits.
 * Invoked in Nutss Ghost Story when Murphy tries to convince Molly that Shepard's alright by reminding her that Mouse hasn't had his usual reaction to Outsiders around Shep.

Film
"Ace: "So, animals can sense evil.""
 * Simultaneously referenced and used straight in Ace Ventura. When Ace is making the acquaintance of Roger's dog on the crime scene, the dog barks at Lois Einhorn when she walks in:


 * He later learns that.
 * Shortly after he has been attacked by a werewolf in An American Werewolf in London, all sorts of animals start hissing and growling at David. The only exception is wolves. They don't seem to mind him too much.
 * In Arachnophobia, both a cat and a dog can sense that the General is, if not technically evil, than certainly not to be messed with. A crow does not realize this in time.
 * In Cello, the family's pet dog, Sunny, barks loudly when it is near the titular musical instrument.
 * Robin Williams described Flubber as this.
 * Lester the family dog barks at Michael Myers hiding behind the bushes in Halloween.
 * In the film version of Hannibal, Hannibal Lecter breaks into Agent Krendler's house and his dog is initially hostile, but Hannibal actually makes the dog cower in the corner while he pokes around.
 * In Disney's The Little Mermaid, Eric's dog absolutely loves Ariel. However, he hates Vanessa (Ursula's human alter ego) and growls at her, giving her a literal Kick the Dog moment.
 * In The Lost Boys, Nanook growls at Michael, after he drank some of the blood-in-a-wine-bottle while hanging out with the vampire hoodlums.
 * In Near Dark, the earliest sign that love interest Mae is not all she seems is that the hero's horse goes nuts when he tries to show him to her.
 * In both the 1961 original and the 1998 remake of The Parent Trap, the dog owned by one of the twins reacts with barking and growling when the other twin, pretending to be her sister, tries to greet him.
 * In Sleepwalkers, the villains morph into somewhat feline creatures, but are hated by actual cats.
 * Dogs could detect Terminator robots in the movies of the same name.
 * In Hook, Nana the dog senses that the titular Captain is about to invade the Darling home and starts barking.
 * In the short film adaptation of Stephen King's The Road Virus Goes North, the protagonist is dumbfounded as to why dogs bark madly at him wherever he goes. They're actually disturbed by the cursed picture he's got in his car. When the titular Road Virus himself first appears, the Evil-Detecting Dog falls instantly silent except for a few terrified whimpers.
 * Also used in the Stephen King miniseries Rose Red, where an otherwise nice dog bites the powerful, autistic psychic Annie. While Annie is not exactly evil, she does retaliate by causing rocks to fall from the sky and crush the house of the people who own the dog, so the dog's attitude was arguably justified.
 * In the film Alien, the cat is able to detect the titular creature, though no-one apart from Ripley seems to be aware of this.
 * In the teaser for the H.P. Lovecraft Historical Society's adaptation of The Whisperer in Darkness, a scholar listens to a wax cylinder recording of a man spouting occult ravings while a cat sits impassively nearby. Suddenly ANOTHER voice cuts in on the recording, and the cat startles and hisses.
 * In In the Line of Fire, Pam's dog growls aggressively at "James Carney", who is really would-be Presidential assassin Mitch Leary, and.
 * In the obscure Spanish film Nocturna, all the cats in the Cat Shepherd's pack start to go and yowl at a wall. The Big Bad of the film, the Shadow, is then revealed, slipping out of the, um, shadows.
 * In Snow White And The Seven Dwarfs, all the animals instantly realize the Witch is evil even while Snow White herself is Genre Blind.
 * In Cloverfield, when the trio head into the subway system to hide, they find dozens of rats scurrying away from the rear end of a darkened tunnel. One of the characters, Marlene, is Genre Savvy enough to realize they have to get away from the area the rats were running away from. Minutes later a giant parasite attacks the group and injures Marlene, who dies a nasty death from the infected bite.
 * Wolf in The Journey of Natty Gann reliably warns Natty of all kinds of impending trouble.
 * Super 8: All the dogs in the area run away to other towns because they can tell there's a monster running around.
 * The Lord of the Rings: The Horses have every reason to be scared of the mountain where the Dead live. For once, the Humans understand the reasons of their fear.
 * The film specifically inserts a scene in which a Hobbit's dog cowers and retreats in fear from a Ringwraith.
 * Kelly's dog Ginger in Race with the Devil is the first to notice the cultists. It later gets hanged from the RV's door.
 * Used a lot in the 1944 film The Mummy's Ghost, in which dogs barking the alarm or biting at his ankles actually pose a greater obstacle to the mummy's comings and goings than anything the human characters do.

Literature
""I realize how trite this sounds- like the inevitable dog in the horror story which always growls before his master sees the sheeted figure- yet I cannot suppress it.""
 * In the sixth book of Jim Butcher's series The Dresden Files, Blood Rites, Harry comes into the possession of a puppy, who he names Mouse; during it, he growls at people that Harry later learns are evil. Mouse grows up to be a very, very large dog, and is explicitly identified as a Temple Dog: the descendant of a spiritual creature who bred with a normal dog, with a couple of supernatural abilities, mostly of the detection or warning variety. He's also way smarter then a normal dog, occasionally looking like he understands English to a degree.  Mouse's breed is in such high regard that Ancient Mai, one of the most powerful and nastiest wizards, will accept its judgment and testimony without second thought. Also Nicomedeus, a 2,000 year old demon-possessed sorcerer and leader of a bunch of other demon-possessed people is apparently afraid of Mouse.
 * Harry's first pet, a large housecat named Mister, gets along fine with the supernatural... so long as it's not an immediate threat, or else interrupting his dinner.
 * Funnily enough, while Mister is big, he's tiny compared to Mouse, yet he constantly bosses Mouse around. Anyone who's ever owned a large dog and a smallish cat know that's totally Truth in Television, especially if the cat was able to establish its dominance while the dog was still a puppy.
 * The protagonists' pet dog in the first Goosebumps book, Welcome to Dead House barks around everyone in town since it can tell that they are actually dead. Eventually, the dead people get fed up with it and actually kill the dog as a result.
 * Likewise in Ghost Beach, where
 * In Samuel Taylor Coleridge's Christabel, one of the first signs something is not right with Lady Geraldine is the untypical reaction of the dog: "The mastiff old did not awake,/ Yet she an angry moan did make!/ And what can ail the mastiff bitch?/ Never till now she uttered yell/ Beneath the eye of Christabel."
 * Susan Cooper used this more than once in The Dark Is Rising.
 * In Over Sea, Under Stone and Greenwitch, Captain Toms' dog Rufus fears and dislikes the minions of the Dark.
 * In The Grey King, Bran's dog Cafall guides Will onto the Old Way, and later attacks one of the foxes that serve the titular character.
 * Gavin de Becker's book The Gift of Fear claims that dogs will growl at untrustworthy people because their owners will detect the malicious intent and broadcast their discomfort with subconscious cues.
 * In Arthur Conan Doyle's "The Adventure of the Creeping Man" Sherlock Holmes asks "Why does Professor Presbury's wolfhound, Roy, endeavour to bite him?" Answer:
 * "Silver Blaze", by contrast, famously includes "the curious incident of the dog in the night-time" - the curious incident being that the dog did not bark at an intruder, thus alerting Holmes to the fact that the dog knew the intruder, therefore the crime in question must have been an inside job.
 * Pretty much universally true in H.P. Lovecraft's works. (Below are just a few examples.) On the other hand, humans have almost the same ability, as Lovecraft's narrators and characters constantly go on about how eldritch and wrong the things they encounter feel (or seem or look or smell or sound), even if they can't explain why or don't even clearly see anything.
 * In The Dunwich Horror, the weird (and unnatural) Wilbur Whateley carries a gun for self-defense against other villager's dogs. A dog still gets him in the end. In a library, of all things. And just to show just how much dogs hated him, it actually crashed through a plate glass window in order to attack Wilbur.
 * In At the Mountains of Madness, the expedition's dogs go nutzo over the strange beings they found frozen in a cave under the glacier.
 * Lampshaded in Rats in the Walls, though it was a cat rather than a dog.

"An icy trickle disturbed Conan's spine, and he wondered if, after all, Pelias were a man, or merely another demon of the pits in a mask of humanity."
 * The Starks' direwolves in A Song of Ice and Fire will growl at anyone their masters don't trust, and in at least one instance, someone they trusted but really shouldn't have.
 * In Andre Norton's Victory on Janus, the garth guard dogs, like the Iftin, can distinguish the Deceptively-Human Robots from true humans and true Iftin by smell.
 * In Sourcery, the Patrician's dog, Wuffles, growls at the sourcerer's staff.
 * In J. K. Rowling's Harry Potter novels, the cat-like creatures called Kneazles explicitly have this ability. Crookshanks is part-Kneazle. When Ron realizes that this is the reason Crookshanks hated so much, he holds his new owl in front of Crookshanks to test his reaction; Crookshanks's lack of interest is good enough for Ron.
 * In the book The Zombie Survival Guide, dogs can sense zombies, reacting with maddened rage unless having been born in fully zombie-infested times. Taken further, in World War Z, dogs are specifically trained for zombie-fighting, helping escort special forces teams and scouts, and with smaller, tough breeds, going into areas humans cannot fight safely in.
 * Although all other animals take the second variety; one way of telling if a zombie is near you is if the wildlife is unnaturally quiet. This comes in quite handy in bogs, rainforests, etc., but applies everywhere.
 * Also in World War Z, one safe zone is shown using dogs in kennels arranged along a walkway as a screening process for refugees entering the city. If the dogs go nuts when you walk by...well, sucks to be you.
 * In The Lord of the Rings animals react strongly to the presence of the Ringwraiths. In the books, the wraiths' horses (and later fell beasts) are an exception, due to being trained from birth to tolerate them. The first movie features spiders, wetas and other creepy-crawlies moving to get away from the wraiths, although the horses look quite evil.
 * A dog specific example would be Farmer Maggot's dogs who really didn't like the Ringwraith who came visiting.
 * Which doesn't really mean much, in the case of those dogs. They're guard dogs, they don't like strange intruders in general. Frodo admits to being terrified of them, due to an incident in his youth when Farmer Maggot caught him stealing mushrooms and ordered the dogs to run him off the property, which they enthusiastically did.
 * In one book of Mercedes Lackey's Dragon Jousters, the tamed dragons - who are established as being as smart as bright dogs - hiss and go into threat displays whenever they see a Magi. This might just be because they watch their riders' body language and know that the riders hate the Magi.
 * In the Saga of Darren Shan, cats and dogs hate vampires (and presumably vampaneze) though wolves, bats and rats love them. In The Vampire Prince,
 * In The Bone Doll's Twin, dogs instantaneously dislike Tobin because he.
 * Subverted in a Father Brown short story. In the beginning, a young man is telling the story of a murder case where, he claims, his dog told him when the murder took place by howling, and who the murderer was by barking at him. Father Brown thinks about the story for a week, and then tells his own interpretation to the young man. This interpretation is based on having the dog acting entirely as an animal, it points to another person as murderer, and it is of course the correct one.
 * Grey in Night Watcher doesn't start out like this, but, after his owners are killed by a vampire, he eventually learns to identify them, resist their Psychic Powers (or even turn them against them by seeming very scary!) and kill them, leading to a Roaring Rampage of Revenge that doubles as a Crowning Moment of Awesome. Yes, he is a dog.
 * A Christmas Carol: "Even the blind men's dogs appeared to know him; and when they saw him coming on, would tug their owners into doorways and up courts; and then would wag their tails as though they said, 'No eye at all is better than an evil eye, dark master!'"
 * In Let the Right One In, cats have an immediately hostile reaction to vampires and attempt to kill them on sight.
 * In Marley and Me (a true story), the titular Marley goes from being a typical goofy, playful, exuberant Labrador to ferocious attack dog when the author's neighbor is assaulted. Earlier, he again does a 180 in demeanor when he senses the authors and his wife's sadness after miscarrying and quietly rests his head in her lap, making him a Sadness Detecting Dog as well.
 * The Saga of the Noble Dead features Chap and Shade. As majay-hi, descendents of Fay-possessed wolves, they have the innate ability to sense the presence of undead.
 * In Robert E. Howard's Conan the Barbarian story "The Scarlet Citadel", Pelias scares away a giant snake by letting it look at him. Conan is very afraid that it was an evil-detecting snake.


 * Tuck Everlasting has cows. Yes, cows that follow a dirt path and quickly go around the forest that the main character flees into. That's one of the reasons why the humans also stay away.
 * One young adult horror novel (can't remember the name) had a once-human snake woman terrorizing the protagonists. As an unnatural monstrosity, she was such an Enemy to All Living Things, that the zoo's fennecs (tiny desert foxes smaller than domestic housecats) tried to attack her from their enclosure. In the end, the heroes trick her into one of the animal pens and the frenzied animals tear her apart so thoroughly she is unable to regenerate.
 * In Perdido Street Station, Lublamai's pet badger Sincerity is the first one to detect the threat of the runt slake-moth, growling downstairs as it emerges from its cocoon in Isaac's loft.
 * Inverted in the Belgariad, birds seem to instinctively know (and love) Polgara, even if they've never met her. The Emperor's bird even chews him out for not recognizing her.

Live-Action TV
"Carlos: Something about your friend I should know? Sarah: Cat person."
 * The Twilight Zone episode "The Hunt" depends on this trope, and one of the characters remarks: "...a man, well, he'll walk right into Hell with both eyes open. But not even the Devil can fool a dog!"
 * The Terminator thing is repeated in The Sarah Connor Chronicles with dogs detecting Cameron as a Terminator.
 * What's especially odd is that even a robot dog could detect Cameron.

"Buffy: He scared the pig! *Giles looks at her* ...Well he did..."
 * War of the Worlds: "Amongst The Philistines", Kensington and Mrs. Pennyworth buy a dog just in time to have it react badly to Adrian, a few scenes before he turns out to be an alien. The trope is pretty blatant here, as the dog was introduced in this scene, and is never seen (alive) again.
 * Happened in The Dukes of Hazzard when Boss Hogg's good twin came to town, and Rosco's dog was used to prevent Boss from stealing his inheritance.
 * On Dexter (and the novels it's (loosely) based on), animals in general and dogs in particular can't tolerate the presence of the main character (a sociopathic serial killer). It's so bad that when he tried to keep a pet turtle it starved to death rather than come out of its shell when he fed it.
 * There's a dog that seems rather fond of Trinity in the fourth season, though.
 * In Reaper, the first sign that The Devil has taken possession of Sam's soul is that dogs suddenly hate him.
 * In Star Trek: The Original Series, it turns out that tribbles can detect disguised Klingons.
 * There's an evil detecting plant in the episode "The Man Trap" - it shrinks away from the human-disguised salt vampire.
 * In Star Trek: Enterprise, captain Archer's dog barks when a web-like alien passes in the conduits overhead.
 * In Heroes, Mr. Muggles always seems to know which characters shouldn't be trusted. Unfortunately, being a Pomeranian, he's not exactly in a position to do much about it.
 * Mr. Muggles licked Sylar's shoes and let himself be picked up by Sylar without fuss, when Sylar was at the Bennet house. So he's not the best judge of character. Of course, Sylar seemed to like Mr. Muggles, too.
 * Not really evil detecting, but in My Own Worst Enemy the family dog is the only one who can tell when its owner's hard-edged split personality takes over.
 * Invoked in Psych. Shawn is trying to fake a haunting in a house, and uses an electronic silent dog whistle to make a homeowner's dog start barking angrily. He then claims the dog is sensing an evil presence.
 * In the first episode of True Blood, a dog barks at resident Friendly Neighborhood Vampire Bill Compton.
 * In Prue's penultimate appearance on Charmed, she is changed into a dog so she could be able to detect the cries of a Banshee (who, by the way, is a possessed Phoebe) and lead Piper to her.
 * They also used to have an Evil Detecting Cat which hisses at and has been known to run from evil beings and demons, especially those trying to fool their way into the Halliwell household by appearing mortal.
 * Invoked once in Supernatural when Sam used this to explain why a dog kept barking at a house where a supernatural event had happened. It was never proved on screen, though.
 * Subverted in Battlestar Galactica Reimagined, when Cylon D'Anna is quite pleased that Jake the dog doesn't react with hostility to her. Of course, little does she know that Jake serves La Résistance in another way.
 * A light version of this appears in NCIS when Kate is reluctant to adopt a dog whose owner has died...until it growls at her Handsome Lech colleague who's always making unwelcome moves on her.
 * In Tales of the Gold Monkey, Jake's one-eyed dog Jack growls or barks at any impostor, including the (unknown-to-the-characters) resident Nazi spy.
 * Episode 6 of Buffy the Vampire Slayer, 's change to evil is detected by a pig. Justified in that


 * Subverted all the time on It Takes a Thief—the big, mean-looking dog the family owns as a thief deterrent is much more likely to approach the thief in a friendly manner or run away whimpering.
 * In The X Files, "Terma", Soviet assassin Peskow manages to upset all the horses in a stable by calmly observing one of them. Though for all we know it was part of his plan.
 * In The Event, dogs bark at the aliens, who are otherwise indistinguishable from humans
 * Happened several times in Forever Knight. A dog and a horse both reacted negatively to vampiric presences.
 * Xena: Warrior Princess had Argo, her trusty horse that could tell something was wrong when Xena's body was hi-jacked by Callisto's spirit.
 * In The Nanny, while C.C. wasn't evil (supposedly,) she was a full-blooded Rich Bitch, and her Pomeranian Chester had no trouble letting her know it. He would snarl and growl every time she was anywhere near him, while being perfectly friendly to everybody else in the house. In real life, despite Lauren Lane (C.C.) being a very sweet and pleasant person, Chester was Fran Drescher's real life dog, and was so fiercely loyal to her any time Lane picked up the dog, he would just naturally growl, so they wrote it into the story that way.

Music

 * Suggested by Loreena McKennitt's version of W. B. Yeats' "The Stolen Child", about mysterious faeries that seduce and steal away the titular child, which begins and ends with a chorus of barking hunting dogs who have detected the sinister faeries.

New Media

 * After this news report hit the internet, 4chan started claiming dogs could "sense" members of the site.
 * In Tales of MU, dogs can detect the main character's ancestry and are utterly hostile to her. This naturally results in her being afraid of them.
 * In the Ted the Caver webfiction, a Jack Russel terrier named Trip refuses to go into a sinister cave the protagonists are investigating.

Tabletop Games

 * The setting of Palladium's Rifts RPG takes the ball and runs with it; not only are animals explicitly said to be sensitive to supernatural evil, but one faction has genetically engineered anthropomorphic canines ("Dog Boys") specifically to exploit this ability as anti-supernatural police.
 * A Dragon article on alternate familiars gave a spellcaster with a dog familiar a bonus to sense motives, using this trope as the reasoning.
 * The world at large hates Prometheans, and animals aren't any different. While Prometheans aren't evil, they are soulless and unnatural, and animals can instantly sense this and often move to attack. Of course, there's a whole school of Transmutations that allows them to redirect this rage in creative fashions...
 * Vampires also have trouble dealing with animals unless they know the Discipline of Animalism, being living corpses. Conversely, if they do know Animalism, they can seem like a Friend to All Living Things.
 * Reversed in GURPS. The effect comes from entities with the Frightens Animals disadvantage rather than special powers that dogs have.
 * In D&D natural animals will usually refuse to approach a variety of undead creatures, so this can be a good way of searching for them.

Video Games

 * Not exactly evil-detecting, but at one point in Metal Gear Solid 3 you need to put on an enemy uniform and mask to infiltrate a base. Scientists, guards, and security cameras take you for the real deal and don't raise alarms. But you don't smell like the officer you're impersonating, and guard dogs will still raise alerts.
 * Also, in Metal Gear Solid, Sniper Wolf's wolf-dogs are unfooled even by your Optic Camouflage. The only way to get past them without hassle is to have one of the puppies piss on your cardboard box, or to have Wolf's handkerchief equipped.
 * Parodied in Kagetsu Tohya. Shiki learns that a black cat frequents the Tohno mansion courtyard, but only lets Hisui approach it, and he wryly comments that animals really can sense dangerous people. Akiha and Kohaku are decidedly not amused...
 * In Mega Man Legends, a local dog knows that Tron Bonne (a Pirate Girl) is up to no good.
 * Similiar to the MGS example, Attack Dogs in the Command & Conquer: Red Alert series detect spies that can fool any other unit and your base defenses.
 * The third game one ups this by replacing the Soviet Huskies with ARMORED WAR BEARS!!!
 * In Snatcher, it's commonly believed that animals can detect Snatchers, to the point where genetically engineered "Pocket Pets", which can be used as purses, are becoming extremely popular.
 * In Mother 3, Lucas, Kumatora and Duster eat some unusual mushrooms while desperate for food. The mushrooms cause them to hallucinate that the monsters in the area are characters from their pasts. The party dog, Boney, is the only one not fooled, and whines and barks when the hallucinations begin to talk to the characters, attempting to warn the rest of the party as to their true nature. He also refuses to get into a beautiful sauna the party can rest in - if you visit it again after the effects of the mushrooms have worn off, you'll find the humans were.
 * In Super Paper Mario, there is a large guard dog-esque monster in Merlee's mansion who is chained up. When released, he runs past Mario and chases off the mansion's maid, who is actually one of the Big Bad's minions, the shapeshifting Mimi.
 * Despite disguises, dogs in the Hitman series will often, if not always, sniff Agent 47 out.
 * Some enemies in World of Warcraft have watchdogs that can see through stealth.
 * Hunter pets will also occasionally stop dead in their tracks if they detect a stealthed hostile mob or player. One of the many reasons for a Hunter to learn to keep an eye on their pet.
 * The warlock pet Felhunter (bascially a demon dog) used to provide his allies with increased stealth detection. These days, the Voidwalker instead does something similiar while he uses his selfhealing ability Consume Shadows.
 * In Geist, dogs can sense you as a ghost, and know something is up when you're possessing somebody. The Big Bad knows this and exploits this, keeping dogs at various checkpoints to make sure you don't escape through a soldier. You can't escape in ghost form, due to energy shields that only let solid matter pass through.
 * In Pokémon HeartGold and Pokémon SoulSilver, your Pokemon will react negatively to the Persian Statues (which are actually security cameras) while inside the Rocket Hideout.
 * Used in Super Robot Wars Advance. The pet dog from Zambot 3 is able to detect that something is kinda off to the protagonists, . Axel gets a typical bark, but the dog barks louder to Lamia,.
 * Koromaru in Persona 3. He's the first sign nonhumans can have a Persona (his, appropriately, is Cerberus).
 * A literal case in Nethack, where your pet (typically a dog) will hesitate to step on cursed items.
 * In the Dragon Age Origins "Stone Prisoner" DLC, Dog will immediately sense that  is something powerful and evil  . The Mabari were bred by a wizard, and it's stated in the original game that the reason Marbari originally became so popular in Ferelden was because they can detect werewolves.
 * In Red Alert 3 Paradox, you need to use each faction's animal scout unit to detect stealth units, giving not only Evil Detecting Dogs but Evil Detecting Bears, Hawks, Tigers, Sharks, and Giant Robot Crabs.
 * Works awesomely well in Fallout: New Vegas: in one of the final missions of the game, . Subverted since you discover , making this arguably more of a They Have the Scent. Played straight if you have the Animal Friend perk and use a lender-dog to do the same thing.
 * In The Sims 3, cats and dogs will "investigate the strange sim" if there is a vampire nearby and there will be a talk bubble on their head with a picture of bats.
 * When you first enter the main city in Shining the Holy Ark you see one of the villains walking around. A cute little puppy starts barking like crazy at her, a flash of light blinds you, she's gone and so is the puppy leaving a crying child.

Webcomics

 * Similar to The Parent Trap example: see a particular webcomic modernization of The Prince and the Pauper.
 * Blip: The comic begins with K taking her dog Poo for a walk, and Poo begins barking at a man on the sidewalk. Said man turns out to be an angel in disguise.
 * Freefall's inveterate kleptomaniac, coward and alien spaceship captain Sam Starfall notes that perceptive canines always give him trouble. Florence, a Bowman's wolf, inverts this: while she is quite aware of, and works to thwart, her captain's moral failings (by human standards), she still seems fond of him.
 * In Pandect - Ice (a Canine Ace: a dog with a human body and soul) can read a person's character by looking into his or her eyes.
 * In Girl Genius, there was no way to detect The Other's mind-controlling parasites (short of an autopsy, one assumes), so Well-Intentioned Extremist Klaus Wulfenbach found and sponsored a Mad Scientist capable of engineering something that can. The "wasp eaters" as a type of construct don't breed true or maybe at all, and have some sort of implants.
 * Naturally, they quickly became priority targets for minions of The Other. After the old the Bug Hunters were nearly wiped out and scattered, one wasp eater wound up as Agatha's pet and later got reverse engineered without harm to itself, and published the results right when the demand went all the way up (between the latest Heterodyne heir automatically being the fount of fashion and The Other's attack where the entire subcontinent couldn't help but notice it).
 * Mittens the cat in Parallel Dementia hisses to snap Fall out of a Nightmare-induced trance.
 * In Wooden Rose, The cat does not approve of Aidan.

Web Original

 * In Marble Hornets and Seeking Truth, dogs do not react well to the presence of the resident Humanoid Abomination
 * In Everyman HYBRID, Alex's dog Sparky detects The Rake long before its first attack on Alex, and may well have been keeping The Rake from attacking while Sparky was in the room. Interesting given The Rake itself is a freakish dog-man.
 * The Onion Radio News: "Family Dog Barking At Evil"
 * Reddit has rapist_sniffing_dog and racism_sniffing_dog.

Western Animation
"Rolf: The stench of immortal doom still thickens the air, yes? Or perhaps it is Wilfred's cabbage evacuation. Hard to tell."
 * Parodied in Family Guy: Trying to score a date with his crush, Death steps into her pet store to talk to her. The animals inside raise such a commotion that they can't hear each other.
 * Also, Brian the dog is the only one who realizes Stewie is evil. Of course, that is more that he is the Only Sane Man on the show.
 * In Samurai Jack, a mouselike creature accepts food from him, but hisses and runs from his traveling companion Ikra
 * In the somewhat forgotten kids' cartoon The Magician, an Identical Stranger (thanks to plastic surgery) kidnaps and switches places with the eponymous main character, taking care to plant a behavior modification chip on his pet dog to ensure it will bark distrustfully at the real guy, and stop doing so at him, which is useful to fool the sidekick.
 * Radarr, Team Pet of the Storm Hawks, detects evil in two episodes that were broadcast consecutively.
 * In "Best Friends Forever", Big Bad Cyclonia disguises herself as an ally of the team. At first, only Radarr is able to sense that something's wrong.
 * In "The Black Gorge", Radarr is suspicious of a seemingly harmless animal who eventually transforms into a monstrous Gorge Sloth.
 * Inverse example: In Batman the Animated Series while Harley Quinn, recently released from Arkham and out trying to start anew, her hyenas immediately start barking at the sight of Bruce Wayne. Harley for her part is clueless that she happens to be standing next to Batman.
 * Also, in Batman Beyond, Bruce Wayne's dog Ace can be quite aggressive towards the bad guys. In Batman Beyond: Return of the Joker, he attacks the Joker.
 * Played fairly straight on The Simpsons "Bart Sells His Soul": after Bart sells his soul to Milhouse, the dog and cat both growl at him.
 * In an episode of the Spider-Man and His Amazing Friends 80's series, Aunt May's puppy became a living lie detector, since thanks to her sense of smell she could point out who had his or her place stolen by shapeshifting villain The Chameleon.
 * A variation in Re Boot: Enzo's dog Frisket is a pretty good judge of character, but he hates Bob, the main hero.
 * In the Gargoyles episode "City of Stone: Part 3", Bronx starts clawing at one of the tapestries just as Goliath and the clan are about to implement Xanatos's plan to end Demona's curse. When the gargoyles are gone,
 * In another episode, he takes a liking to an Irish teenage boy, but growls and barks at his female friend. Turns out that
 * Jonny Quest TOS episodes.
 * "Skull and Double Crossbones". When Jose asks Bandit if he wants to be friends, Bandit growls at him. Later we learn that Jose is The Mole, a spy for the Chief of a crew of pirates.
 * "Shadow of the Condor". When Bandit first meets Baron von Freulich he growls at him. Later von Freulich tries to murder Race Bannon.
 * In the Galaxy Rangers episode "Mindnet," the first clue to the characters that all is not right is when Icarus and Winter (a pair of cybernetically enhanced dolphins) protest that "Goose" is behaving strangely. (The first clue to the audience is that  voice actor is trying to imitate Doug Pris and isn't doing very well).
 * The Zillo Beast in Star Wars: The Clone Wars is able to tell that Palpatine is evil and upon escaping from its cell, rampages through Coruscant to hunt him down for that and Palpatine being the one sentencing the creature to death.
 * Avatar: The Last Airbender:
 * Appa and Momo are very good at detecting malicious intent in humans. Appa growls and reacts defensively towards the sandbenders (who later capture him) and Momo hisses at the pirate captain and his weird bird thingy. In fact, it's Appa licking Zuko that makes Aang wonder if he's really changed.
 * On the other hand, the Earth King states of his pet bear: "if there was any danger at all, Bosco's animal instincts would sense it." Granted, Bosco had been apprehensive around Azula, but the King had misread that as exhaustion; when he uses this line, it is in extreme error.
 * In Sequel Series The Legend of Korra episode "And the Winner Is.." the fire-ferret Pabu sits peacefully by the radio while music plays but hisses at it and jumps away when Amon pulls a Do Not Adjust Your Set in the middle of the music program.
 * Somewhat inverted in Kim Possible, where pretty much all the villains seem to hate Rufus, but they like him if turned good (both Shego and Draken can be called as witnesses)
 * In the Ed, Edd 'n' Eddy episode 'Run for your Ed', the Kankers lost their 'Ship Inna Bottle' due to Ed's sleepwalking. They decide to search the Cul-de-sac in their usual chaotic mischief, which results in mass destruction. Prior to that, Rolf's animals catch on to their impending visit and all flip out (from his goat standing stiff, his chickens and pig screaming and flailing around, and even a piece of fried chicken seem to give some reaction to Rolf when put against his ear). He quickly carries all his farm animals into the basement and closes it, waiting there for the rest of the episode.

Real Life

 * Dogs (and cats) have been known to react in the alleged presence of the supernatural.
 * Older Than Feudalism: In Zoroastrianism, one of the oldest surviving faiths in the world, the dog is considered one of the most sacred animals, for its ability to detect, and even deflect evil with a mere gaze.
 * Some dogs also seem to be able to sense the presence of tumors and even predict when epileptic owners are about to have seizures.
 * Purportedly, head Scientologist Dave Miscavage's dog.
 * The book "the gift of fear" says that when a dog growls at a shifty person it is actually responding to the owners unease and trying to protect them.
 * Not unlikely at all, given dogs are capable of detecting their masters' emotions, even hidden ones, thanks to their senses. (they can hear a heartbeat speeding up, for one)
 * Dogs are also incredibly attuned to body language, since the bulk of their communication is by that method. Since dogs and people share a number of signals, they can easily pick on things we'd miss since we tend to focus on tone of voice.
 * Seizure response dog and diabetic alert dogs are trained to predict upcoming attack and warn their owners. Even untrained dogs are told to be sensitive for sudden changes and attempt to protect humans from harm- barking, forcing them to lay down or even bite their hands, forcing them to drop sharp objects like knives and scissors before the seizure begins.
 * There is one account of a horse that did the same thing, and would answer math questions and puzzles by reading the unconscious body language of humans present and responding by tapping his hoof or pointing to an object. It was only figured out when a psychologist asked the horse a question nobody knew the answer to, and the horse couldn't figure out how to answer.
 * A specific example is the Pekingese, a dog that Chinese Emperors used to keep inside their sleeves. If the dog bit someone who had been granted an audience with the Emperor, it was a sign they were untrustworthy, which usually meant execution.
 * True crime author Ann Rule's dog always snarled and growled at her friend Ted Bundy and shied away whenever he tried to pet him, despite usually being friendly to everyone. Little did Ann know her friend was a serial killer spending his nights prowling college campuses for victims. Similarly, the cat belonging to the sorority house where he went on of his final rampages apparently ran away the night of his attack. In an interview with one of the surviving victims, she speculated that the cat must have sensed the impending threat.
 * Likewise, the neighbor of Josef Fritzl (the Austrian man who kept his daughter locked in the basement for years and fathered incestuous children with her) insists that his usually-friendly dog absolutely hated him.
 * Not strictly "evil" per se, but almost all animals have some form of precognition when it comes to natural disasters. So, in this case, humanity really is Too Dumb to Live! No, seriously. Ask anyone who's been through a major earthquake. Dogs, cats, horses, birds, they all freak out. And get out, if they can.
 * Most animals can hear the surface noises generated by the initial p-waves of an earthquake, though this sound is too high in frequency for human hearing. Chinchillas, which have hearing abilities roughly similar to humans, are just about the only animal that will not freak out shortly before an earthquake hits.
 * There is a persistent myth that if a dog or horse freaks out, and there is nothing visible to you that should be causing them to do so, one should look at what the animal is looking at. More specifically, to do so by looking between their perked ears. The myth states that you will see the spirits or ghosts that only animals normally see if you do this.
 * Dogs and rats have been trained to detect land mines or gas leaks by smell.
 * In the 19th century miners used to keep small birds for that purpose. Hence the phrase "canary in a coal mine."
 * Despite the above examples, this trope shouldn't be relied on in Real Life, as plenty of animals make a habit of reacting badly to strangers in general, or to specific types of people (all men, tall people, folks wearing hats, etc.), regardless of demeanor or intent. That said, it's probably not a good idea to ignore it altogether either.
 * Not quite "Evil" exactly, but any animal that can not detect (and prevent) a predator's "Evil" attempt to eat them, will not be around to breed the next generation of evil detecting animal. This applies to most dangers as well.
 * Particularly true of snakes, which many animals' brains are hardwired to notice even if they're camouflaged.
 * The "evil" aspect depends on a subjective value, but there's Lucky and Flo, two black Labradors that the MPAA praised for their ability to sniff out counterfeit CDs (and legitimate ones).