The mouse at the center of the Korean fingernail folktale · OpenClipart public-domain illustration
Last verified: September 25, 2026 · Netflix performance and Korean folktale source reviewed.
Netflix’s Mousetrap begins like a modern identity-theft thriller.
Reclusive novelist Moon-jae discovers that his fingerprint no longer unlocks his phone. His passwords fail. His money, name and social identity start slipping into someone else’s hands.
But Netflix did not invent the central idea from scratch.
The series is built on an old Korean folktale in which a rat eats a person’s discarded fingernails and takes on that person’s form.
Mousetrap, released August 28, reached No. 1 on Netflix’s global non-English TV list in its second week with 4.4 million views. The older story behind it is now reaching viewers who may never have heard the childhood warning about throwing away fingernails carelessly.
The Korean story existed long before Netflix
KBS World published an English version of the folktale years before the Netflix series.
In that telling, a young man leaves home to study for the state examination at a remote temple.
A mouse begins eating food he leaves behind. It also eats the fingernails he clips and throws away.
Years later, the young man returns home and discovers another man already living there with exactly his appearance.
The double knows the family and behaves convincingly enough that the young man’s own parents believe the double is their real son.
In this version, even his own family accepts the double as the real man and drives the original out.
The story later resolves through the help of a cat, which exposes the double as the mouse.
Details can change between tellings. It is safer to describe a documented version than to claim that every Korean version contains exactly the same judge, family member or ending.
Why fingernails?
The story depends on an older idea that a small part of the body can retain a connection to the person it came from.
KBS World’s telling explicitly explains a traditional belief that a person’s nails carry something of the person’s spirit, allowing the animal that repeatedly consumes them to assume that person’s form.
Similar fears about hair, blood or nails exist in other cultures too.
In the Korean folktale, however, the discarded fingernail creates an especially ordinary route into danger.
The victim does not open a cursed tomb or perform a forbidden ritual.
He clips his nails and throws them away.
A minor everyday act gives the impostor access to his body and then his place in society.
That is what makes the story useful for a modern identity-theft thriller.
The frightening part is not the duplicated face
If the mouse merely copied the man’s appearance, the folktale would be a simpler monster story.
The more disturbing part is that the double occupies the victim’s social position.
His family believes the impostor.
The original person cannot prove that he is himself.
His physical appearance is no longer enough because someone else possesses the same appearance and has already been accepted by the people around him.
That mechanism survives almost intact in Mousetrap.
The tools have changed.
Netflix turns family recognition into digital recognition
Moon-jae lives as a reclusive novelist and has spent years largely outside ordinary social contact.
That makes his modern identity especially dependent on systems rather than on frequent face-to-face recognition.
His phone recognizes a fingerprint.
Banking systems recognize credentials.
Accounts recognize passwords.
Government and financial records recognize names and numbers.
When those layers begin accepting somebody else, saying “I am the real Moon-jae” is not enough.
The family accepts the double and rejects the original.
Mousetrap
Phones, accounts, records and people stop confirming Moon-jae’s identity.
The old story’s stolen “place” becomes a much larger bundle in the digital version: money, devices, records, social relationships and proof of identity.
Official Netflix K-Content trailer with English subtitles.
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The route is folktale → webtoon → Netflix
The Netflix series is not a direct period adaptation of the oral tale.
There is another step in between.
Mousetrap is based on the Kakao webtoon Field Mouse, which also draws on the fingernail-eating rat story.
The creative path is therefore:
Korean folktale → Kakao webtoon Field Mouse → Netflix series Mousetrap.
The webtoon and drama keep the central anxiety — somebody else takes your place — while building a contemporary crime and pursuit story around it.
Director Kim Hong-sun has also described the traditional tale as the project’s starting point.
Why the English title changes the emphasis
The Korean title is 들쥐, literally “field mouse.”
The webtoon is introduced in English as Field Mouse.
Netflix uses the global English title Mousetrap.
That shift slightly changes the feeling of the title.
Field Mouse points directly toward the creature from the folktale.
Mousetrap suggests the pursuit structure of the thriller: Moon-jae and the people around him are trying to identify and catch the figure known as “The Rat,” while Moon-jae himself is trapped inside a system that no longer recognizes him.
The global title therefore emphasizes the chase without removing the older folklore underneath it.
The series became a global hit after release
Before August 28, the Korean folktale was mainly useful as background to understand the premise.
After release, there is a stronger current signal.
Netflix’s official weekly Top 10 report says Mousetrap reached No. 1 on the non-English TV list with 4.4 million views for the week beginning August 31.
Its performance should not be reduced to “foreign viewers love Korean folklore.”
There is no evidence that one cultural element alone explains the audience.
The cast, thriller structure, webtoon source, Netflix distribution and direction all matter.
The folklore is useful for a different reason.
It answers a specific question international viewers can ask after watching:
Was the rat that eats fingernails and becomes a person a real Korean folktale?
Yes.
Netflix modernized it, but the underlying warning predates the show by generations.
The old fear still works because identity has become harder to see
In the folktale, the impossible part is a mouse acquiring a human body.
In the drama, much of the fear can be built without literal magic.
Modern identity already exists across systems most people cannot physically see: authentication records, financial accounts, device access and databases.
A person can look exactly the same while the systems around him insist that something is wrong.
That makes a very old Korean story unusually easy to translate into a contemporary thriller.
The rat once stole a man’s face and family position.
Mousetrap asks what happens when the thing being stolen is the entire network of evidence that tells modern society who a person is.
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