Fry: Close. (pulls down the hoods to reveal they're both purple-haired cyclopes)
Leela: They... are my parents.
Maybe The Hero is undercover to avoid a Frame-Up. Maybe they touched the wrong artifact and became a Baleful Polymorph. The point is, they're looking different, often monstrous. Then someone (often their loved ones, for dramatic impact) catch them with their personal effects. Uh oh. Our hero has just been Mistaken for Own Murderer. Now they have to correct the mistake, and fast, before the people who made the mistake kill them in retribution for their "murder".
- The Batman Adventures: Downplayed. In Issue #8, Summer Gleeson is supposed to have a date with a man who, unbeknownst to her, was Clayface under a disguise but arrives on time to see Clayface being arrested and wonders what happened to her date.
Summer: I was supposed to meet somebody here. Tall, blond... handsome. But I don't see him anywhere. Did... that thing...
Batman: No, Miss Gleeson. The person you described... was never here.
- In the Doctor Who (Titan) Ninth Doctor story "The Transformed", some superpowered teens think that alien gargoyle-like creatures are killing and disappearing them. In fact, the condition that gave them the superpowers causes them to mutate into the gargoyles.
- Iron Man used to be known for body guarding Tony Stark. On an occasion where he couldn't take off the suit, Stark's disappearance made people suspect Iron Man.
- Princeless: Princess Adrienne's Dad thinks she was killed by the mysterious knight who destroyed her tower. The knight is Princess Adrienne.
- In Action Comics #303: "The Monster From Krypton", red Kryptonite transforms Superman into a dragon-like creature called a drang. When he holds his cape to communicate the change, Jimmy Olsen thinks the monster killed him and alerts Supergirl and the army.
- In Swamp Thing, government agent Matthew Cable, encountering the title character for the first time, believes that he's Alec Holland's murderer. Eventually the Swamp Thing manages to convince him that he is Holland or so he and everyone assumes prior to the Alan Moore retcon.
- In the Land Before Time fanfic The Seven Hunters, the gang of seven wishes for the power to defeat the T-Rex Red Claw and get their wish in an unexpected way by being transformed into meat-eaters. After realizing their children are missing, the gang's parents find the transformed kids and chase them out of the valley with murderous intent under the mistaken assumption that they had killed their children.
- In Wargs and Peace, a Hobbit fanfic, Thorin is transformed into a warg by a bolt of lightning. After a few days of unsuccessfully trying to convince the company of his identity, he is spotted trying to get his cloak sheltered (which fell off during the transformation) the company believes that the warg has actually killed him, and attempt to hunt him down.
- In Ben 10: Destroy All Aliens, a Galvanic Mechamorph goes on a Roaring Rampage of Revenge against a Tok'ustar whom he believes killed his son Azmuth. However, it is revealed in the end that the Tok'ustar is Azmuth because of a glitch in the Omnitrix.
- In Brave, Fergus stumbles on Elinor's torn dress and then on her bear-self attacking Merida. He nearly kills her before he discovers who she is.
- In Brother Bear, Kenai and his brother Denahi are tracking down the bear who killed their oldest brother Sitka. Kenai corners the bear and kills it, but the spirits turn him into a bear directly afterwards. When Denahi arrives on the scene, he sees Bear!Kenai and thinks it is the bear that killed Sitka, surmising that it killed Kenai too. He spends the rest of the movie tracking down Kenai to kill him for...killing Kenai.
- Invoked by Yzma in The Emperor's New Groove. She tells the guards that Pacha and Kuzco (who has been turned into a llama) murdered the emperor (Kuzco).
Kuzco: No, wait! I'm the emperor! It's me, Kuzco!... They're not listening!
- In Shrek, Donkey thinks an ogress ate Fiona after he finds one in her room. She calms him down enough to tell him that it's her curse.
- In both the film and the original novel The Princess Bride Buttercup believes that the Dread Pirate Roberts killed Westley. Only when he tumbles down the hill shouting "As...you...wish..." does she realize that he is Westley.
- The Empire Strikes Back features a justified example of this (considering the Motivational Lie Luke was told about Darth Vader killing his father), resulting in the original Luke, I Am Your Father reveal. Played with in that, to some extent, Vader thinks of Anakin as a different person who died.
- Animorphs: As the team works to evacuate their parents before the Yeerks can get to them, Rachel shows up in her kitchen in bear morph. Rachel's mother immediately tries to defend herself with a spice rack, but on hearing her daughter's voice in her head, Rachel's mom thinks the bear ate her alive.
- The Chronicles of Narnia: When Eustace from The Voyage of the Dawn Treader wanders away and is involuntarily transformed into a dragon, his companions frantically search the island for the missing boy. On first sighting Eustace as a dragon, they initially assume he's the monster that ate Eustace, although he's able to prove his identity with body language.
- In the Father Brown short story "The Mistake of the Machine", a man in ragged clothes is accused of murdering Lord Falconroy, because he set off a lie detector when Falconroy's name was mentioned. Being identified as a conman who operated ten years previously seems to clinch it. It turns out he is Falconroy dressed up for a "slum dinner", and had just been about to say so when he was (it seems correctly) recognised as the conman.
- In Saki's "The Lost Sanjak", a man swaps clothes with a dead man to ditch his identity after an affair; unfortunately, by leaving his own clothes on the corpse, he becomes a suspect in his own murder and ends up hanging for it!
- In the Sherlock Holmes story "The Man With The Twisted Lip", the titular man is actually the gentleman he was accused of murdering in disguise. A rare example where he was not trying to prove his identity. He didn't want to shame his family with the revelation that he'd been begging as an occupation.
- Carl Hiaasen novel Bad Monkey features the main character investigating the mysterious disappearance of a Medicare fraudster, believing that his wife and her mysterious new boyfriend killed him for the insurance money. Then, it turns out that the new boyfriend is her husband in an assumed identity and they faked his death in order to collect the insurance money and escape a police investigation.
- In the Are You Afraid of the Dark? episode "The Tale of the Hunted", while on a hunting trip, Diana gets turned into a wolf. Her father sees her wolf self in her cabin and assumes she killed her. Diana evades the hunting posse until the transformation wears off.
- Buffy the Vampire Slayer: In "A New Man" Giles has been transformed into a Fyarl demon which is thought by the gang to have killed Giles.
Buffy: (stabbing Demon!Giles) This is for Giles!
Giles: (in demon language, which only Spike understands) For me?
- Colonel March of Scotland Yard: In "The Strange Event at Roman Falls", the wife of famous reclusive writer is accused of his murder after she reports him falling off the cliff near their home into the sea. However, it turns out the writer never existed at all. He was a Moustache de Plume created by the woman to allow her to publish her works and be taken seriously. However, after an old romance rekindled, she decided to fake the death of the fake husband to allow her to marry her love.
- Doctor Who:
- When the Ninth Doctor regenerates, Rose thinks this stranger has done something to the Doctor and demands he brings him back.
- In "The Witch's Familiar", Missy convinces Clara to get into a Dalek exo-suit and pretend to be a Dalek with her as a prisoner. Upon finding the Doctor, Missy claims that she's the Dalek that killed Clara, with the Doctor starting to believe her due to the Dalek system preventing Clara from telling the truth. It's only by Clara getting the suit to say "Mercy", something a Dalek would never say, does the Doctor realize something's amiss and opens the exo-skeleton to find Clara inside, before giving Missy a Tranquil Fury-filled Get Out! for nearly tricking him into killing his best friend.
- The Incredible Hulk is suspected in the death of David Banner, because no one knows Banner's secret.
The creature is wanted for a murder he didn't commit. David Banner is believed to be dead and he must let the world think that he is dead until he can find a way to control the raging spirit that dwells within him
- Argentine series Lalola (and its multiple Foreign Remakes) focuses on Lalo, a man who is turned into a woman by a spell placed on him by a scorned lover. He then adopts the name of Lola, and is accused of Lalo's murder towards the end of the series.
- An episode of Tales from the Crypt has a man working with his coroner brother to fake his death for a huge insurance payout. After getting plastic surgery, he waits at an island for his wife to join him with the payout. When she fails to, he flies back home to discover she's now married to his brother and they're both living large off the settlement. The man calls the cops to turn them in for fraud only to discover the surgery is so good and the fake murder done so well that they don't believe he's really him. In fact, they're convinced the only way he could know so much is if he's the killer so the man ends up arrested, tried, convicted and sent to the electric chair for his own murder with his last words being telling everyone who he really is!
- In The Good Person of Szechwan, Shen Te has a male alter ego, her fictional cousin Shui Ta, which she adopts to deal with problems that she can't handle in her female self. Toward the end of the play, her problems have multiplied to the point that she's living as Shui Ta continually, and her neighbors are wondering where Shen Te has gone. One of them hears her sobbing in a back room and goes to the police with a suspicion that Shui Ta is holding Shen Te prisoner. When the police search the house and find a bundle of Shen Te's clothes but no Shen Te, Shui Ta is arrested for Shen Te's murder.
- A non-murderous variant occurs in Dario Fo's play Trumpets and Raspberries, in which an industry mogul is under arrest for his own kidnap after a case of Mistaken Identity followed by restorative Magic Plastic Surgery.
- Invoked by Kokichi and Kaito in Danganronpa V3: Killing Harmony. In a desperate bid to defeat the mastermind, they set up a plan in which no one, not even the cameras, can determine which of them killed the other. Kokichi convinces Kaito to kill him in a hydraulic press. However, they film the murder to make it appear as though Kaito had died and make it impossible to examine the body. During the trial, Kaito hides in an Exisal, using a voice modifier and a script prepared by Kokichi to impersonate him and confuse everyone. The point was to nullify the game by making a murder Monokuma couldn't judge fairly, though the plan failed after Shuichi saw through the charade and exposed Kaito as the killer.
- Exploited by the head of the monsters in one area of Dragon Quest VII. It strikes a deal with the local priest, claiming that as long as the priest lives in a cursed, monstrous form, it will leave his hometown and everyone living there alone. However, the transformed man is forced to return home and try to live among the residents, who naturally tend to assume that he killed the real priest and is mocking them. In other words, the monster expects them to invalidate the deal by killing the transformed priest themselves, at which point it can swoop in and finish them off...
- Metal Wolf Chaos: Invoked by the usurper Vice-President Richard Hawk, after his initial attempt to kill President Michael Wilson in a coup d'etat failed thanks to the President having a Humongous Mecha called "Metal Wolf". As Wilson and his supporters are forced on the run following Hawk's takeover, Hawk releases propaganda newscasts denouncing "Metal Wolf" as the President's assassin and a terrorist "meaner than Satan himself!"
- Reversal of the Heart sees a Princess getting turned into a dragon as vengeance for her lover the Prince killing the child of a mother dragon. Upon hearing the commotion resulting from the sudden transformation, the Prince sees a dragon stumbling among the tattered clothes and smashed furniture of his beloved and assumes the worst. He spends the rest of the short on a Roaring Rampage of Revenge against the "dragon."
- In Dragon Mango, this is the reason Mango doesn't know who her father is. His name is Steen Dragonsbane. One day, he saw a dragon seemingly attacking a city and severely wounded it. The dragon fled, and he was distracted by the appearance of a badly wounded woman from the humanoid dragonslayer species. While she recovered, they bonded, ran away from her disapproving people, and got her pregnant. One day, he returned to her only to find her missing and that same dragon appearing over her clothes. Assuming the dragon to have eaten his lover, he attacked her and she fled. To this day, he doesn't realize that the dragon was his lover, a dragon with Voluntary Shapeshifting in her true form, and has made it his life's mission to wipe out dragonkind.
- Aladdin: The Series: Aladdin and Iago come across a young lady's footprints which gradually change into those of a jackal. This leads the two of them to think that the strange woman who's been trying to scare them away has just been eaten by a jackal, instead of realizing that she is the jackal.
- American Dragon: Jake Long: When Trixie and Spud chance into photos of Jake turning into his dragon form, Spud assumes the dragon ate Jake. Trixie quickly points out the correct conclusion.
- On Buzz Lightyear of Star Command, Buzz and Mira are exposed to Zurg's latest evil concoction that transforms and fuses them into a single amorphous blob creature unable to talk. When Booster and XR find the blob next to Buzz and Mira's empty uniforms they assume it ate them.
- In the Fantastic Four: World's Greatest Heroes episode "Hard Knocks", Susan tells Reed that the Hulk killed Bruce. Reed renders the Hulk unconscious, undoing the transformation and revealing his Secret Identity.
- In the Futurama episode "Leela's Homeworld", Leela thinks the mutants who spied on her killed her parents, when in fact they were her parents. Her parents, so ashamed of being mutants and so desperate for their child to live a happy life free of the stigma of being one (they forged alien documents to make her orphanage think her minor mutation of having one eye was because she was an alien), tell her she's right and are actually about to let her kill them in vengeance before Fry intervenes and tells her the truth.
- Shimmer and Shine: In "The Mysterious Tower", Zac finds a necklace that turns him into a Ziffilon-like monster. Kaz briefly assumes the monster ate Zac.
- On SpongeBob SquarePants, SpongeBob and Patrick fall in love with one of Sandy's pets, a caterpillar named Wormy. When Wormy transforms into a butterfly overnight, they, having never seen such a thing, assume it's a monster that ate Wormy... and it'll come after them next!
- Steven Universe has this as the conclusion to an important murder mystery arc. Despite what Homeworld records said, Rose Quartz did not kill Pink Diamond. Pink Diamond faked her own death and made out her alter ego to be responsible, in order to force the other Diamonds to leave Earth alone.
- In one episode of Visionaries, Leoric gets Mode Locked as a lion, and his fellow Spectral Knights who know he shapeshifts into a lion assume this other lion killed him.