Miguel is an employee that works for Cormac McCarthy on his ranch. He is a major fan of McCarthy's work and wishes to emulate his style.
In the episode The End, Miguel meets with the Mystery Team to give them copies of McCarthy's unfinished book, while warning them of the Chupacabra. That night he is murdered by the creature, but returns as a ghost similar to Marquess of Queensberry. He reveals he was the actual author of the book, and knowing that he could properly emulate McCarthy's style was a major accomplishment.
He leaves the scene wanting to throw a fiesta, not knowing that he's actually dead.