Chekhov's Gun/Harry Potter

If the Chekhov's Armory in Harry Potter were an actual army, it would curbstomp everyone in a massive Zerg Rush. Also, there may be unmarked spoilers. Please list examples by book:

Harry Potter and the Philosopher's/Sorcerer's Stone

 * The Mirror of Erised.
 * Harry's scar.
 * Harry's eyes, as well. Adult characters who knew the Potters will always say that Harry looks like his father but has his mother's eyes.
 * The flash of green light from.
 * The bezoar mentioned briefly in Harry's first potions class is later used in Book 6
 * The tongue-tying curse mentioned in Harry's first visit to Flourish and Blotts, which keeps from telling the location of  in Book 7.
 * Probably the one that holds the record for longest intro-to-relevance time is . Introduced in the first chapter of this book, it then becomes critical to the plot about halfway through Book 7.
 * The Snitch from Harry's first Quidditch match sat around for six-nearly-seven books before being useful for more than just being, well, an awesome catch. 'Course, we should have seen that coming, given that it was caught specially, and this IS a Harry Potter book.
 * In the scene where Harry goes to buy his wand, Olivander comments rather offhandedly that Harry's father, James, "favored a mahogany wand. Eleven inches. Pliable. A little more power and excellent for transfiguration." Well, good for him, because that surely must have come in handy later when he undertook becoming an Animagus, as is revealed in the third book.
 * In the same scene, he reveals that Harry's wand and Voldemort's share their core's source, which becomes important at the end of Goblet of Fire.
 * Hagrid mentions that his flying motorbike belongs to Sirius Black;.
 * When Harry is attacked by in the Forbidden Forest and is rescued by Firenze, the other centaurs object, citing "the stars." Even Firenze himself mentions to Harry that he hopes that he and his fellow centaurs have been misreading them. Considering the fact that centaurs are particularly gifted at astrology, they're probably seeing.
 * Ron's spell to turn Scabbers yellow. Maybe Fred and George weren't wrong about it working on rats. They hadn't tried it on an
 * Chekhov's Boomerang: The Dumbledore card from the Chocolate Frog, functioning in this book and in Deathly Hallows.
 * Chekhov's Gift: The Invisibility Cloak, which Harry gets for Christmas, not only helps him throughout the series but turns out to be in Book 7.
 * Rather hilariously, there was a book released a short time before the book that discussed Chekhov's Guns from the books. It concluded that since so many people knew about the Invisibility Cloak at this point (reasoning that Snape told Voldemort) that the cloak had no more bullets left to fire. Boy was it wrong.
 * There is a scene in Harry Potter and The Order of The Phoenix where Moody mentions that his Invisibility Cloak is starting to lose its powers (hinting that Harry's cloak is special in some way, because it isn't losing its at all).
 * Hagrid mentioning that he was expelled from Hogwarts.
 * Hagrid explaining how secure Gringotts is, that dragons guard the high security vaults, and also how unwise it is to try double-crossing Goblins (or otherwise pissing them off).
 * Chekhov's Gunman / Chekhov's Army: Numerous characters, including:
 * Nicolas Flamel.
 * Mrs. Figg is introduced as Harry's babysitter, and we hear very little of her afterward. In Book 5, she's revealed to be.
 * , mentioned in passing on, and not mentioned again until Book 7, where he's critical to the plot.
 * Petunia Dursley. While she's established as an important character, a reader may wonder why Dumbledore brought Harry to live with his horrible, abusive relatives or why Harry in the later books even bothers to return to the Dursleys' home at the end of each school year. In Book 5, it's revealed that.
 * Sirius Black, mentioned in passing by Hagrid at the beginning of the book, and not mentioned again until he ends up being the for most of Book 3.
 * Snape is introduced and is a major character, but it takes a few more books before we realize just how important he is.
 * Others include Griphook, Olivander, and Scabbers.
 * First Girl Wins.
 * Chekhov's Classroom: The one that holds the record in the series as the most inconspicuous is, briefly mentioned in passing by Snape in class; it then shows up again in Book 6, when Harry . It's also used by Harry to.
 * Chekhov's Skill:
 * The Wingardium Leviosa levitation charm.
 * Ron's skill at
 * Harry's ability to is assumed by Harry and the readers to be, but we later learn that he's.
 * The ability of Animagi to change themselves from human to animal form. Shown being done in this book only by McGonagall, but then turning out to be very important when done by other characters in the later books.
 * "Could Snape possibly know they've found out about the Philosopher's Stone? Harry didn't see how he could, yet he sometimes had the horrible feeling that "
 * This gets more attention in the film than anything, but

Harry Potter and the Chamber of Secrets

 * Many things in this book come back and play an important role in book six.
 * Some examples:
 * ~Chekhov's Skill~: "They can carry enormous weight, "
 * Mundungus Fletcher is mentioned in passing by Arthur for having tried to hex him during a raid. Mundungus becomes important in books five through seven.
 * At Borgin and Burkes, Malfoy notices the Hand of Glory, a magical artifact that gives light only to the holder.
 * The same scene also mentions the
 * Chekhov's Boomerang: The flying car is used to take Harry from the Dursley's house. Then again to fly to Hogwarts and

Harry Potter and the Prisoner of Azkaban

 * The newspaper photo of the Weasley family's vacation.
 * ~Chekhov's Gunman~: Sirius was mentioned in passing way back in the first chapter of the first book. This is when the reader really starts to realize just how much planning went into these books, and kicked off the frenzied search for what other hints and clues might pay off later.
 * Also, and to a much lesser extent Crookshanks.
 * Professor Trelaweny, at the end of the book, Dumbledore casually mentions that he should give her a raise, since the prediction she made about Wormtail turned out to be true, and that it was the second accurate prediction she had ever made. At the end of OotP, it's revealed what the first one was.
 * Snape seemed to be the only teacher zealously trying to find Sirius. He's even willing enough to kill him and eager enough to watch the dementor's suck out his soul.
 * Also, quite a few of the predictions done in the Divination Classroom turns out to be truer than one would've think!
 * Just a few sentences later we also know that.
 * Predicting that someone will die isn't exactly much of a spoiler. Rowling even says with the Flamels that living forever isnt all it's cracked up to be.
 * Trelawney also predicts that Hermione drops out of Divination class by Easter. Even if she probably did not know it herself at the time.
 * Trelawney also predicts that Hermione drops out of Divination class by Easter. Even if she probably did not know it herself at the time.

Harry Potter and the Goblet of Fire

 * Chekhov's Gunman: Bertha Jorkins, ,
 * Chekhov's Gunsnake: Nagini is introduced in the seemingly unrelated first chapter and is not featured significantly until the next book, when Voldemort orders her to attack and Harry
 * Dumbledore's brief look of triumph when he is told that Voldemort used Harry's blood to resurrect himelf. It is one of the reasons why Harry survived the Killing Curse in the final book.
 * Chekhov's Skill: The Unforgivable Curses.
 * The flash of green light Harry kept remembering in the first book. Revealed in this book to be.
 * During the Yule Ball, Dumbledore makes mention of having a Potty Emergency and discovering a room with "a really rather magnificent collection of chamberpots. When I went back to investigate more closely, I discovered that the room had vanished." Perhaps, Dumbledore theorizes, the room only appears when somebody really, really needs it...

Harry Potter and the Order of the Phoenix

 * Harry begins having dreams early on in the story about locked doors and winding passages.
 * A portrait at St Mungo's insists Ron must have spattergroit; Ron retorts he's just freckled. In Deathly Hallows,.
 * The thestrals, and Harry being able to see them.
 * When Hagrid reappears after an unexplained absence, he's seen badly bruised and scarred.
 * Hermione makes a list containing the names of all the people agreeing to be in the DA.
 * In Chamber of Secrets, a passing mention was made to Peeves breaking a cabinet, preventing Harry from getting into trouble. It's mentioned here again, which the Weasley twins push one of Umbridge's hench-students in, and he gets trapped there for months because it's magical.
 * "Snape's Worst Memory".
 * Chekhov's Boomerang: The mirror Sirius gives Harry becomes this in Deathly Hallows.
 * Chekhov's Gift: Near the middle of the book, Sirius gives Harry a magic mirror Made horrifying when you realize that the driving point of the climax of the book is that
 * Chekhov's Gunman: Mrs. Figg, introduced in Book 1 as Harry's baby-sitter, and then not mentioned again until this book.
 * The barman of the Hog's Head Tavern, identified two books later as . It was even noted that he "looked vaguely familiar".
 * who is mentioned in passing and the becomes important to the plot in Book 7.
 * , a seemingly minor character who, in true JK Rowling style, ends up being important to both this book's plot and that of Deathly Hallows.
 * Professor Trelawney. In Book 3 Dumbledore casually mentions that he should give her a raise, since the prediction she made about  turned out to be true, and that it was the second accurate prediction she had ever made. At the end, it's revealed what the first one was.
 * This is also the book where we start to see Neville's emerging combat skill, along with his determination, both of which become of great importance in Deathly Hallows.
 * This book also contains an example of what happens when you overuse Chekhov's Gunmen. Harry refers in passing to a Mark Evans while speaking to Dudley. This is a throw-away character who is never mentioned again, but many assumed he would have some importance in the future because he had the same last name as Harry's mother. JK Rowling publicly apologized for it.
 * Chekhov's Skill: Occlumency.
 * The Quibbler, and the fact that Luna Lovegood's father is the editor.
 * The Quibbler, and the fact that Luna Lovegood's father is the editor.

Harry Potter and the Half-Blood Prince

 * When Harry he marked the spot with a bust of a warlock wearing a wig and
 * To add to that, the
 * Tonks' Patronus changing its form. The fact that it's supposed to represent
 * Chekhov's Boomerang: Books 2 and 6 parallel each other and they are essentially the same basic plot, only six is much quieter and softer, and the roles of Harry and Ginny are apparently reversed. In the second book, Ginny harbored strong feelings for Harry and had a bewitched diary which was able to take control of her. This book was destroyed by Harry to save Ginny's life. In the sixth, Finally, there is the matter of the numbers of the books. In total, there are seven books. Numbers 2 and 6 are the first and last even numbers in a sequence of 7.

Harry Potter and the Deathly Hallows

 * Chekhov's Boomerang: Sirius's mirror.
 * Chekhov's Gunman: Kreacher, Dobby, Aberforth, Grindlewald.
 * Chekhov's Gunman: Kreacher, Dobby, Aberforth, Grindlewald.