History Fridge / HarryPotterAndTheHalfBloodPrince

** Perhaps the Draught of Living Death and "love" potions are there for cross curriculum purposes with Defence against the Dark Arts? The principle of 'offense informs defense' is common in advanced courses, and since NEWT potions is a requirement for Aurors, that would explain why these dangerous potions are in the 6th and 7th year syllabi.

* The Gaunts' birth defects are very pronounced, as if they've been marrying within their own family for several generations. While the number of pure-blood families was declining in Britain, there were still at least [[https://www.wizardingworld.com/features/who-are-the-sacred-twenty-eight 27 other such families at the time]], many of whom were also wizard supremacists, like the Blacks, Lestranges, and Malfoys. But considering the Gaunts were proud of not just being pure-blood, but being Parseltongues and descended from Salazar Slytherin and Cadmus Peverell, they may have been arrogant and entitled even by their peers' standards. Crosses over with Fridge Horror.

* Harry writes a Defense Against the Dark Arts essay at one point and later reflects that he "fully expected to receive low marks on his, because he had disagreed with Snape on the best way to tackle dementors”. Harry almost definitely wrote about the Patronus Charm, but it seems odd that Snape would have tried teaching the students an alternative way, since the Patronus is the only thing we've ever seen have any effect on dementors whatsoever. It becomes FridgeBrilliance when you realize that of course Snape wouldn't want to teach the class Patronuses because he'd certainly be expected to produce one as a demonstration, which [[spoiler:would reveal his Patronus's form and might cause someone to realize that it matches Lily's]]. Snape may have even had to come up with his own way to counteract dementors over the years so that he could avoid casting a Patronus for this reason.
* Imperiusing Stan Shunpike might seem like an odd move for the Death Eaters, but it actually makes sense when you think about it. Stan is the conductor of the Knight Bus, which is not only one of the biggest modes of transportation for wizards, but is also fairly discreet in its own way. Apparition and the Floo Network can both be traced, but the Knight Bus doesn't seem to magically track its passengers. Having control over Stan allows the Death Eaters to keep an eye on anyone who might be travelling by Knight Bus to hide from them, and also to ride it themselves without being apprehended.

* The Sectumsempra spell which [[spoiler:almost made Draco bleed out]] is noted as "for enemies" by its creator...Gee, who were those enemies? Answer? [[spoiler:Sirius and James.]] And if the memory in ''Order'' is anything to go by, he tried to use it on [[spoiler:James]], though it was weak, nonverbal, and to the face instead of to the chest. However, the very fact that he didn't massacre them, [[spoiler:especially after that trick with the Whomping Willow when Lupin was transformed]], shows tremendous self-control.

* By the early twentieth century, the Gaunts are down just Marvolo, Morfin and Merope. The Gaunts were infamous for marrying their own cousins to "keep their family pure". [[BrotherSisterIncest And there are no cousins left for Morfin and Merope to marry]]. Yikes.

* Why is Snape so furious when Harry uses Sectumsempra on Malfoy? Because it's a lapse in Snape's Unbreakable Vow to protect him from harm at all costs. And it's a spell ''Snape invented himself.''

** It also explain why, of all the organizations fighting Voldemort during the Battle of Hogwarts in Book 7, the Dumbledore's Army is the one that suffer less casualties ([[spoiler:Fred Weasley, Colin Creevey and Lavender Brown]]). Harry's teaching style was more consistent that all the teachers they had put together.

** Not only is it distributed openly--''they teach sixteen-year-olds how to make it.''

* Tom Riddle Sr was raped. Okay, he ''did'' marry Merope, but he ''was'' under Amortentia, basically uberpowerful roofies. She kept him enslaved to her will for several years after forcing him to leave his family for her, stopping only when she fell pregnant with his child. And we readers blame him for ''getting the fuck away from her when he realized what she did to him''.

* By the early twentieth century, it's heavily implied that the Gaunts are down just Marvolo, Morfin and Merope. The Gaunts were infamous for marrying their own cousins to "keep their family pure". [[BrotherSisterIncest And there are no cousins left for Morfin and Merope to marry]]. Yikes.

* The Gaunts' birth defects are very pronounced, as if they've been marrying within their own family for several generations. While the number of pure-blood families was declining in Britain, there were still at least [[https://www.wizardingworld.com/features/who-are-the-sacred-twenty-eight 27 other such families at the time]], many of whom were also wizard supremacists, like the Blacks, Lestranges, and Malfoys. But considering the Gaunts were proud of not just being pure-blood, but being Parseltongues and descended from Salazar Slytherin and Cadmus Peverell, they [[UpToEleven may have been arrogant and entitled even by their peers' standards]]. Crosses over with Fridge Horror.

*** It's also hard to imagine that either Marvolo or Morphin was a good and patient teacher.

** As Potions Master, of course Snape would only want the highest scoring students, because at this point, [[FridgeHorror if something goes wrong]] you end up with BodyHorror instead of HilarityEnsues.

* Dumbledore has an ulterior motive for wanting Slughorn back at Hogwarts -- he needs Slughorn's Horcrux memory.

** Even if the luck potion only benefits the drinker, the effects still make sense. Ron was becoming increasingly paranoid about even being seen by Lavender, it was only a matter of time before he started pestering Harry to borrow his Invisibility Cloak so he could vanish from her completely. The longer Ron puts off the breakup, the more annoying it is for Harry. Ron and Lavender finally breaking up is really lucky for Harry.

* The Felix Felicis Harry won from Slughorn in this year's first Potions Lesson. As it needs half a year to be made and Slughorn had only one month and a half, there wouldn't have been enough time to create it just for this occasion. This Felix Felicis was actually Slughorn's emergency stash in case the Death eaters got hold of him, he wanted to drink it in order to make it easier to escape. But now when he was safe and sound in Hogwarts, he felt safe enough to give it away as he was under Dumbledore's protection.

* One from the film: in the book, Harry and Dumbledore have to walk to Hogsmeade in order to apparate to the horcrux cave, and then return to Hogsmeade before flying back to Hogwarts. Because of time constraints in the film, this gets changed to them apparating directly to and from Hogwarts, with Dumbledore addressing the impossibility by saying "Well, being me...has its privileges." How so? Well, since he's taught there for almost all his adult life (several decades), he would know better than anyone else about the protective enchantments (both the ones that have been there for centuries and the recent additions in the wake of Voldemort's return) and would therefore know how to penetrate them.

* The Gaunts' birth defects are very pronounced, as if they've been marrying within their own family for several generations. While the number of pure-blood families was declining in Britain, there were still at least [[https://www.wizardingworld.com/features/who-are-the-sacred-twenty-eight 27 other such families at the time]], many of whom were also wizard supremacists, like the Blacks, Lestranges, and Malfoys. But considering the Gaunts were proud of not just being pure-blood, but being Parseltongue and descended from Salazar Slytherin and Cadmus Peverell, they [[UpToEleven may have been arrogant and entitled even by their peers' standards]]. Crosses over with Fridge Horror.