"Con la Iglesia hemos topado" ("We stumbled upon the Church") is a popular misquote of Con la iglesia hemos dado, Sancho ("We found the church, Sancho" - small letter, as they are talking of a physical building) from Part II, Chapter IX. The stock phrase version is used in Spain to express annoyance at the meddling or lobbying of the Catholic Church (the institution) in a political matter.
"Ladran, luego cabalgamos" ("They bark, therefore we ride") or "Ladran, Sancho, señal que cabalgamos" ("They bark, Sancho, sign that we ride") is also attributed to the book but it actually comes from Goethe's 1808 poem Kläffer ("Barker"; obviously, without the interjection of "Sancho": But their strident barking / is only a sign that we ride"). In its stock phrase version, it's used to say that an attack from one's enemies over a recently taken action is a sign that you are doing the right thing. There is an even more insulting version, "Ladran, señal que son perros" ("They bark, sign they are dogs"). It appears that the phrase became popular due to the famous poet Ruben Dario, who frequently used it to shut his critics regarding his origins.
"A donde fueres, haz lo que vieres" ("Wherever you go, do as you see") and its multiple variations. A lot of people think this idiom comes from the book, or rather that it's a variation of the quote, "Cuando a Roma fueres, haz como vieres" ("When you go to Rome, do as you see"). Although the quote does appear in the book, it was not originated there, as it actually comes from the 4th century, when it was first uttered in Latin by the bishop Ambrose of Milan.
Interestingly, there also an example within the work itself when Quixote threatens an enemy with the quote "ahora lo veredes, dijo Agrajes" ("as Agrajes said, you will see now"). Agrajes is a character of the famous chivalry romance Amadís de Gaula, but he has no such line in the work. It's unknown whether Cervantes committed a honest mistake or was deliberately making Quixote err to further imply his insanity, but the quote became a semi-popular idiom nonetheless. A posterior version freely expanded the idiom to a rhyming "ahora lo veredes, dijo Agrajes con todos sus pajes" ("as Agrajes said with all of his pageboys, you will see now").
"Too much sanity may be madness and maddest of all. To see life as it is, and not as it should be" is often attributed to the book in the United States, but actually comes from the musical Man of La Mancha.
Defictionalization: In the prologue to Part II, Cervantes jokes that he'd accept an invitation from the Emperor of China to run a school where they teach the Spanish language and the story of Don Quixote. The Cervantes Institute now has two centers in China; one in Beijing, another in Shanghai.
Genre-Killer: Credited with killing off romances of chivalry, although, to be fair, they were already falling out of fashion and becoming unfashionable themselves.
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 keep asking for a sequel because Money, Dear Boy, even although 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 (which he did), and the second part of La Galatea (which he never got to do). 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.
A species of the prehistoric horse Hipparion, Hipparion rocinantis, was named after Don Quixote's steed.
A prehistoric clam discovered in La Mancha was named Dulcineaia manchegana. Similarly, the modern sedge species Carex quixotiana was named so primarily due to being native to the area around La Mancha.
The beetle Ardistomis quixotei was named after the main character to commemorate the 400th anniversary of the story's publication, which fell around the time of its discovery.
Lohuecotitan pandafilandi is a giant sauropod from Spain named after Pandafilando, a giant that Don Quixote thinks is one of his enemies.
Torch the Franchise and Run: As noted above, Cervantes was dismayed to see other writers producing unauthorized Don Quixote stories of their own, and wrote Part Two which finishes with Don Quixote regaining his sanity right before dying to give the character a definite ending. Ironically, the character's popularity has produced countless works featuring the character out of Cervantes' canonical story, the most famous of them being likely Alan Moore's The League of Extraordinary Gentlemen.
Write What You Know: The tale of Ruy Pérez de Viedma, a Spanish soldier who was captured by the Turks and Made a Slave aboard one of their galleys, is probably based on the author's own experiences.
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