In Stephen King’s novel The Outsider, the supernatural entity behind the killings is called El Cuco.
El Cuco is a shapeshifting creature that takes on the appearance and identity of other people. In the novel, its ability to imitate a respected local coach creates apparently impossible evidence surrounding the murder of a child. The resulting contradiction drives the investigation and causes the characters to question ordinary ideas about identity and proof.
The name comes from a Spanish and Latin American folkloric bogeyman tradition. King uses the figure in a modern crime-horror story, combining police investigation with supernatural suspense.
The name is sometimes written or discussed as “El Coco” in folklore and in translations, but the English-language novel commonly identifies King’s creature as El Cuco. The Outsider was published in 2018 and later became the basis for a television adaptation.