Genre-Killer: Credited with killing off romances of chivalry, although, to be fair, they were already falling out of fashion and pushing Deader Than Disco.
Magnum Opus Dissonance: At The Cavalier Years in Spain, money was found in Theater, and glory was found in Poetry. When Cervantes wrote a comedy book he didn't know he was creating the first modern novel, and the book didn't get noticed by the critics. Nonetheless, it was successful enough for the editor to kept asking for a sequel because Money, Dear Boy. But Cervantes had Attention Deficit Creator Disorder and wanted to write a lot of projects that would bring him glory, like Los trabajos de Persiles y Segismunda. No one took the comedy book seriously, least of all, Cervantes himself. Maybe that continuation would have never seen the light of day if not for Avellaneda's fanfiction: a Fix Fic, because Avellaneda thought Cervantes wrote some characters deserving of a better writer. Cervantes decided to write the best second part he could and considered Don Quixote a work that would survive centuries.
Write What You Know: The tale of Ruy Pérez de Viedma, a Spanish soldier who was captured by the Turks and Mad A Slave aboard one of their galleys, is probably based on the author's own experiences.