"A lot of the greatest wizards haven't got an ounce of logic,—"Warning: Unmarked spoilers on this page. You may put examples from both the book and film adapations.
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- The Slytherin House is notorious for producing the greatest number of dark wizards out of any house in Hogwarts.
You'd Expect: Both school and government authorities would take a special interest in ensuring the members of this House were held under special scrutiny. Furthermore, they could try to find out why this pattern has persisted for so long, and what they could do to prevent it. Like, for example, abandoning a tradition in which one in every four students is basically assigned to the evil House.
Instead: No one performs any investigation nor preventative measures, and the House is free to operate in the same way as it always has. There's minor attempts at justification, like "being stuck there doesn't mean you're a bad person," but this does nothing to address the underlying stigma.
- The Polyjuice Potion can give you the appearance of anyone you can get a sample of hair from — not just a clever disguise, but it alters your body so you have the same fingerprints, hair, and body shape. Thus anyone important can be replaced.
You'd Expect: There would be methods of rooting out such impersonations at any location of importance, such as the Ministry and Gringotts.
Instead: The Ministry of Magic has no defense against it, and while Gringotts does, it's only after any potential intruders have passed the front desk and entered the vault area. As a result, the heroes are able to infiltrate both places using Polyjuice Potion. Maybe the Ministry can be cut some slack as we don't know if Gringotts would share its knowledge with them, but Gringotts itself is still getting nowhere near as much mileage out of their security systems as they otherwise could.
- From the second book onwards the same situation repeats itself: some crucial events take place with either no witnesses or kids (usually Harry) as witnesses, and afterwards nobody believes them.
You'd Expect: They would use the Time Turners to send back an invisible observer and oversee the events in question.
Instead: They never do, and it constantly gets worse.
- Dumbledore is revealed to be a highly skilled Legilimens in the fifth book of the series.
You'd Expect: Dumbledore to try using this skill for something, such as finding out who opened the Chamber of Secrets both times in the series. Granted, this might not work, and could be a VERY controversial step, with the students and their parents getting very upset about Dumbledore's mind-reading, but Dumbledore could point out that with someone going around petrifying other students, he's got a very good excuse to take such measures.
Instead: Dumbledore's Legilimency is only used in the fifth book, to find out why some of the events of the climax happened.
- Four students can apparently create a map that is not fooled by Animagi or Polyjuice Potion.
You'd Expect: Dumbledore to have a version of this map somewhere so he can identify the Animagi, people in disguise, or possessed people in the school. Preferably with some kind of alarm if a name shows up that isn't supposed to be there, so he doesn't have to keep looking at it. Or any other important place for that matter: if four kids can make one, surely experienced wizards can imitate it.
Instead: Apparently, nobody thinks of this. Ever. The Marauder's map is used solely for Harry and co. to sneak around the school without being caught.
- House elves can — at the order of their master — use powerful magic, and have a method of transportation that is instantaneous, untraceable and bypasses anti-apparition wards.
You'd Expect: Anybody, hero or villain, to notice that potential and use it extensively.
You'd Also Expect: Wizards to develop and utilise means of protection against house elves' magic.
Instead: Nobody cares. Elves keep being able to go literally anywhere, and no wizard makes use of that until the desperate situation in the last book.
- For his protection from Voldemort, Harry must stay with his abusive aunt, uncle, and cousin from birth to his attendance at Hogwarts, and return there for the majority of the time that he isn't at the school.
You'd Expect: For somebody to check up on him periodically as time went by, to verify that he's being well cared for, and to gradually introduce him into the Wizarding World. Several pivotal people know how important he is in defeating Voldemort, and as future books and movies would show, leaving a young witch or wizard untrained, in an abusive environment can have extremely dire consequences, (for example, one book has Harry blow up Aunt Marge when he's provoked enough, and that's possibly the best-case scenario).
Instead: The only one who sees him somewhat regularly is his Squib neighbor Mrs. Figg. Harry is left alone and abused, without knowing why. Added to the Horcrux that occasionally influences his behavior, it's a miracle that he's as stable as he is. This is made all the more egregious in that among Harry's allies are some very powerful Aurors, one Mama Bear, Dumbledore, and his godfather. And even when they do intervene, it's usually with one-time threats, and nothing for a long-term resolution.
- Dumbledore is aware that someone is attempting to steal the Philosopher's/Sorcerer's Stone, that they were good enough to make a serious attempt to steal it from Gringott's, and there's a strong possibility that it involves Voldemort.
You'd Expect: Him to recruit former members of the Order to protect it, to surround it with spells that only let the right person past them and to keep its location a secret from everyone outside of that very small group of people. Hell, a Fidelius Charm would be enough, and Dumbledore has an extremely skilled Charms user on his payroll.
Instead: He relies on less than competent people like Hagrid to supply guards and didn't quiz Hagrid on potential problems for those guards. Worst of all, his security used obstacles that were really less security and more puzzles. Admittedly they were tricky but first year students were able to get past the same puzzles that were intended to stop a dark wizard controlled by Voldemort. If not for the last spell cast on the mirror you would have to wonder if Dumbledore was unconsciously trying to let Voldemort return to life.
For that matter: Why keep it at the school at all? They can literally teleport anywhere on Earth, and instead it's kept in a school full of the next generation of magic users. Sure, it's one of the most well-protected places in the Wizarding World, but it is also intentionally placing the students in danger of getting caught in the crossfire, combined with the natural tendency of kids to go specifically where they are told not to, which is exactly what Dumbledore says at the start of the year: "Stay away from the third-floor corridor."
- Voldemort, while possessing the body of Professor Quirrell, wants to kill Harry Potter without openly revealing himself so he can remain on-campus to steal the Philosopher's Stone.
You'd Expect: That since he enjoys every possible advantage in this situation (Harry does not yet know he is a bad guy, Quirrell is one of Harry's teachers and in a position of authority over him, he is a fully trained wizard and Harry is an 11-year-old boy who is only beginning to learn elementary first-year spells), he would find it trivially easy to arrange to catch Harry somewhere alone and without witnesses and then murder him in any one of a myriad of possible ways that would plausibly look like an accident, or frame someone else for Harry's murder.
Particularly: If he stunned Harry, then threw him into the room with Fluffy the Cerberus and let him get eaten, which would accomplish multiple objectives at the same time — it would kill Harry while making his death entirely look like "death by misadventure", it would politically disgrace Dumbledore that the Boy-Who-Lived died on Hogwarts grounds from a security measure set up by the school authorities, and it would force either Dumbledore or the Ministry of Magic to order the Cerberus removed from the school as a deadly hazard to students and thus remove the principal obstacle standing between Quirrellmort and the Philosopher's Stone.
Instead: He tries to kill Harry by jinxing his broom during a Quidditch match, which means his murder attempt is done in broad daylight, in front of hundreds of spectators, and in such a manner that Harry is literally not yet back on the ground before every observer with the IQ of a houseplant (all two of them) has figured out that someone is attempting to kill Harry Potter.
- Draco Malfoy learns that Harry will be smuggling a baby dragon up to the school astronomy tower at midnight, and makes plans to get him caught.
You'd Expect: Malfoy to either tip off Filch again, like he did for the midnight duel, or inform another member of staff about what Harry's up to.
Instead: Malfoy decides to lie in wait for Harry at the entrance to the astronomy tower, despite having no way of catching Harry by doing so, and putting himself in danger of being caught out of bounds. The result is him getting caught and punished by Professor McGonagall.
- Harry, Ron, and Hermione tell McGonagall their suspicions about Snape being after the Stone.
You'd Expect: McGonagall to immediately haul them into her office and demand exactly what they know about the Stone and how they know it. True, she may believe that they are talking nonsense, but if you are helping to guard a life-or-death secret and eleven-year-olds are able to discuss the secret, nonsense or otherwise, then you have a major security leak. Had McGonagall acted sensibly, she could have found out, not only that Hagrid had let things slip in front of the kids, but that he did the same in front of an unknown party.
Instead: McGonagall sends the kids on their way, threatening them with punishment if they don't butt out, and unwittingly making it necessary for them to go after the stone themselves.
- In the book's climax, the Philosopher's Stone has ended up in Harry's pocket, and Voldemort and Quirrell know this. Quirrell, as described above, is a fully trained wizard, and in this scene he's been casting non-verbal wandless magic, marking him as one of the most powerful wizards we see in the series.
You'd Expect: Quirrell to try and get the Stone by magic. Even if Rowling hadn't thought of Accio or Imperio (a summoning spell and a mind-control spell) yet, Quirrell could just kill him by magic and take the Stone from his corpse. He is, after all, a wizard — magic should be reflexive for him. And despite Harry's protection, it is clearly shown that magic does work on him, such as the ropes Quirrel conjured. As will be noted again later on, a modicum of creativity would have allowed him to kill Harry easily.
Instead: Quirrell runs after Harry and grabs him, getting burned by the magic love protection in his skin. He then tries to strangle Harry, failing for the same reason. Voldemort actually has to tell this idiot to use magic, but by then it's too late as Harry burns him to death.
Chamber of Secrets
- In the beginning of the book, Harry and the Dursleys are having breakfast. It's been established that the Dursleys can't tolerate any use of the word "magic" since Harry is a wizard. Dudley tells Harry to pass a frying pan containing bacon his way.
You'd Expect: Harry to either ask Dudley to say "please" or just give him the frying pan.
Instead: He tells Dudley he forgot the magic word. Dudley falls off his chair at the mention of Harry saying "magic" and Harry gets a shrill talking to from Uncle Vernon.
- Harry and Ron for some reason cannot pass the magical barrier leading to the Platform 9 3/4, but all the other Weasleys are already there, the train has already left, and the boys are afraid that Ron's parents might leave the station another way. Harry suggests that they return to the car they arrived by, because people are starting to stare at them.
You'd Think: That the boys would just go to the car and wait for Mr and Mrs Weasley to get back, since they obviously wouldn't abandon their car. Or, failing that, they could take Professor McGonagall's suggestion after the fact and just send an owl.
Instead: Ron gets a "brilliant" idea to steal the car and fly it to Hogwarts. Car's stealth mode malfunctions, it gets seen by non-wizards, kids get detention, Arthur is fixed with a huge fine, and the Weasleys lose the car.
- Voldemort gives a Horcrux, his old school diary, to Lucius Malfoy, as part of his plan to reopen the Chamber of Secrets, but since he's incapable of trusting anyone, he doesn't tell Lucius what it is, just that it's a powerful magical artifact.
You'd Think: He would tell Lucius that he values the diary's safety more than he does Lucius', and that if Lucius does anything without Voldemort's express orders, death itself will not be enough to save Lucius from very slow, very painful retribution. Hell, Voldy could suggest that the diary has powerful wards on it that will be activated if Lucius uses it without permission, so that Lucius would hesitate to use it in a cavalier fashion even if he was 100% convinced Voldy was dead.
Instead: Voldy does none of this, apparently confident that Lucius would never take any initiative whatsoever regarding Voldy's stuff. So Lucius decides to carry out the plan anyway for his own ends, and gets a portion of his master's soul destroyed.
- Throughout the year, muggleborn students, along with Filch's cat, suffer attacks from an unknown assailant that leave them petrified. Right after the first attack, it is established that a potion known as Mandrake Draught can cure the victims.
You'd Expect: The school to try and buy some of this Draught from an outside source as soon as possible, so that the students can be treated quickly. Granted, the person responsible for the attacks might have destroyed or contaminated all the Mandrake Draught in the country earlier to prevent the school doing this, but we see no evidence to suggest this happened, and in any case, the idea of one person being capable of this seems a bit far-fetched. As a bonus, treating a victim immediately will allow them to identify their mysterious attacker.
Instead: The school decides to make the Draught itself, even going so far as to grow its own Mandrakes. The problem is that the Mandrakes take most of the school year to mature, and therefore become usable. The monster continues attacking people, and it's only through dumb luck that no one dies. Also, the assailant's victims miss out on a substantial part of their education for that year.
- The diary mentioned earlier ends up in the hands of Ginny Weasley, who eventually suspects that it's connected to the attacks on other students. And she's right: It's possessing her and having her set a basilisk on people. She tries to get rid of the diary by flushing it down a toilet, but later discovers that it's in the hands of Harry Potter. Not wanting him to discover her crimes, she steals the diary back. That's understandable, but her next actions really take the biscuit.
You'd Expect: Ginny to try and dispose of the diary a bit more thoroughly than she did last time.
Instead: She writes in it again, and as a result, the diary has her attack two more people (one of which is Hermione) and Ginny herself almost dies. Granted, she probably wanted to confirm how much the diary had told Harry, but it was still a bad idea.
- Harry and Ron have figured out that the monster in the titular chamber is a Basilisk. Shortly after overhearing that Ginny has been taken to the Chamber, and then witnessing the teachers telling Professor Lockhart to deal with the monster, they decide to give him this information. When they do so, they learn that Lockhart, who has supposedly dealt with all manner of dark creatures in the past, is in fact a fraud who takes credit for deeds other wizards and witches have done.
You'd Expect: That, since Lockhart has proven himself to be incompetent at this sort of thing, Harry and Ron would seek out the other teachers and get them to deal with the Basilisk. In addition, given Lockhart was about to wipe their memories and they had to disarm him, they would immobilize him in his office or make sure he's tied up securely with a note explaining the situation.
Instead: They decide to bring Lockhart along anyway. While in the Chamber, Lockhart attempts to abandon Ginny and completely wipe both Harry and Ron's minds in order to stop them revealing his secrets. They only avoid this due to Lockhart using Ron's broken wand, causing the spell to backfire on him. Even if he hadn't tried this, there was virtually nothing he could have done to help the group.
Prisoner of Azkaban
- In the backstory Harry's parents are warned that they've been targeted by the Big Bad and need to hide. They choose a spell that perfectly conceals one's domain, as long as a chosen person (the Secret Keeper), well, keeps the secret.
You'd Expect: They would become Secret Keepers themselves. Deathly Hallows explicitly shows this is possible since during that book, Bill and Arthur Weasley are able to be the Secret Keepers for their respective dwellings. Furthermore, Dumbledore was Secret Keeper for #10 Grimmauld Place in Order of the Phoenix, a place that he was then able to visit and stay in freely.
Or At Least: The Potters would make their Secret Keeper someone they trust absolutely (duh), someone who Voldemort was already 100% determined to murder as priority one (so that being the Secret Keeper doesn't put them in any danger that they weren't in already), someone who is a Master Occlumens (so that Voldemort, a known Legilimens, cannot read their mind), and someone who can straight-up kick Voldemort's ass any day of the week and twice on Sundays (so that Voldemort can't get it out of them by main force). In other words, that they'd use Dumbledore. Who had already volunteered for the job.
Instead: In gross violation of the Evil Overlord List #222 (keep the forcefield generator inside the forcefield) they make another person the Keeper, and it fails. Granted, that person betrays them, but even without that their plan wasn't as foolproof as it could have been.
- James Potter's first choice for his Secret Keeper is his best friend Sirius Black, despite the fear that someone close to the Potters is working for Voldemort. Fortunately for him, Sirius isn't that someone.
You'd Expect: That if Sirius was prepared to die to protect the Potters, he'd accept the Secret Keeper position, and go into hiding so that Voldemort couldn't find him. After all, if you want something done right, sometimes it's better to do it yourself. Also, it would be a good idea to keep a wizarding equivalent to a cyanide pill on him at all times, in case Voldemort does track him down.
Or Better Yet: The Potters would make their Secret Keeper someone they trust absolutely (duh), someone who Voldemort was already 100% determined to murder as priority one (so that being the Secret Keeper doesn't put them in any danger that they weren't in already), someone who is a Master Occlumens (so that Voldemort, a known Legilimens, cannot read their mind), and someone who can straight-up kick Voldemort's ass any day of the week and twice on Sundays (so that Voldemort can't get it out of them by main force). In other words, that they'd use Dumbledore. Who had already volunteered for the job.
Instead: Sirius convinces the Potters to make their other friend Peter Pettigrew the Secret Keeper, his logic being that Voldemort would never think of going after someone like Peter. This is despite the possible traitor within his group of friends. Peter turns out to be the traitor, sells the Potters out, and later frames Sirius for their deaths. And that's not going into the fact that, if Voldemort does go after him, he could easily interrogate Sirius on who the real Secret Keeper was.
- Likewise in the backstory: when the Potters are attacked, Sirius asks Hagrid for Harry, Hagrid says that Dumbledore asked him to come to Privet Drive, and Sirius gives Hagrid his motorcycle instead.
You'd Expect: Dumbledore to raise an eyebrow about why the supposed Dark Wizard and Voldemort's servant Sirius, gave Hagrid means of safe passage for the target of his assassination, and given his interest and knowledge of wrongful imprisonment in Azkaban and Frame-Up (his own father, the House Elf of Hepzibah Smith's, Morfin Gaunt), would take a closer look at the circumstances of Sirius' arrest and capture, especially since he didn't have a trial.
Instead: Dumbledore shrugs and accepts Sirius is guilty, and moves on.
You Also Expect: Sirius accompany Hagrid to Privet Drive to meet Dumbledore in person and inform him about Wormtail and the Secret Keeper change, and also to fulfill his responsibility as Harry's godfather.
Instead: Sirius charges headfirst to find Wormtail on his own without any backup, gets surprised and framed.
In addition to that: You expect Sirius to disapparate or at least disappear or try and chase after Wormtail who he knows changed into a rat after he cut off his finger, or at least try and find some way to defend himself. Instead he goes Laughing Mad and becomes a textbook Not Helping Your Case example.
- In Remus Lupin's backstory: Dumbledore accepted him into Hogwarts, knowing that he's a werewolf and once a month turns into a monster with a love of human flesh for several hours. To get around this problem, Dumbledore decides to build/designate a location near the school where Lupin can safely transform.
You'd Expect: That they would escort Lupin there under an invisibility cloak or disillusionment charm, keep him from learning how to disable the containment mechanism, and stand guard while he's transformed.
Instead: They bring Lupin there without any concealment every time, and while it's implied that Dumbledore keeps remote watch over Lupin, there are no actual guards. As a result, his friends manage to sneak in and even sneak him out for walks which nearly causes some grizzly accidents. What's more Snape sees Lupin being escorted and begins to suspect the truth which eventually nearly leads to his death and Remus' expulsion.
- Years later, during the events of the book proper, Dumbledore employs Lupin as a teacher. This time, however, they have a remedy that allows him to retain his sanity while transformed, so he can just wait through "those times of the month" in his office. The remedy must be taken regularly for several days prior to the full moon.
You'd Expect: That they'd provide for Lupin to have some reminders and a contingency protocol, like a lockdown on his office when the "zero hour" approaches. It's not some flu medicine he's taking — it's supposed to keep him from going rabidly insane in a castle full of children.
Instead: Nothing of that kind is done; on one occasion he neglects to take the potion and nearly kills several students.
- Related to that, Snape walks into Lupin's office carrying the Wolfsbane potion, only to find Remus missing and that the Marauder's Map is open with many dots leading to the Shrieking Shack
You'd Expect: Snape with his prior history of visiting the Shack on the night of a full moon, knowing that Remus is about to transform, would carry the Potion with him, and on revealing and visiting the Shack, would first ensure and force-feed that Remus would drink it, if only out of self-preservation, before starting his Who's Laughing Now? spiel on Sirius and Lupin.
Instead: Snape forgets the Potion, forgets to remind Lupin he's not taken the potion, goes crazy about wanting to feed Sirius and Remus to the Dementors, gets knocked out and nearly gets killed by a transformed Lupin, only to be saved by Sirius who diverts Lupin's werewolf form away. Oh and in the process, Wormtail escapes to summon the Dark Lord. Nice work, Snivellus, you truly deserve the Order of Merlin Fudge was contemplating for you before Sirius escaped.
- The Weasleys win the wizarding equivalent of the lottery, gaining 700 galleons, which is, judging by the fact that in the second book they only had one galleon in their vault at Gringotts, significantly more money than they have ever had.
You'd Expect: They would put almost all of it in the bank, using it responsibly and lifting themselves out of poverty.
Instead: They blow most of it on a holiday to Egypt to visit Ron's brother Bill. Go figure. Though they did get Ron a new wand.
- Sirius Black, an innocent man believed to be responsible for the death of Harry's parents, wants to kill Peter Pettigrew, the Traitor who was responsible (who conveniently turned himself into a rat 12 years ago and is still in disguise as Ron's pet) and prove to Harry he's innocent.
You'd Expect: Sirius would try and get in contact with Dumbledore shortly after he escaped from Azkaban, whether by Portkey, Floo Network or something, and explain the truth to him. That way, Pettigrew can be taken into custody, keeping Harry safe, and Sirius would be cleared of all wrongdoing.
Instead: While trying to capture Pettigrew, he violently attacks the Fat Lady's portrait, and later breaks into Gryffindor Tower with a knife drawn. These actions get him no closer to finding Pettigrew, and actually incriminate him further.
- Later on, he turns himself into a dog, grabs Ron and Pettigrew, drags them into the Shrieking Shack, and waits for Harry to follow.
You'd Expect: That first chance Sirius got he would cast the spell to return Pettigrew to human form and explain to Harry what happened.
Instead: He just leaves Pettigrew in rat form. When Harry arrives it looks like a trap, and Sirius says things like "Only one will die tonight" which just confirms to Harry that Sirius wants him dead, making Harry try to kill Sirius.
- Sirius and Lupin are expositing to the trio about their backstory with Pettigrew and the whole Secret Keeper thing. Halfway through, the door opens and closes mysteriously as Snape enters under the invisibility cloak. Ron suggests it's a ghost but Lupin says that the Shack isn't haunted.
You'd Expect: The visible people in the room would investigate the fact that someone invisible obviously just entered. The kids have Lupin and Sirius' wands and might not know the people-detecting spell from Deathly Hallows (which probably didn't exist at this point in the books) but they could at least make an effort (A Very Potter Musical demonstrates one possible method).
You'd Also Expect: Snape would take advantage of his invisibility and stun or otherwise restrain the escaped murderer and his accomplice before getting everyone back to the castle.
Instead: No one does anything. Lupin and Sirius continue to exposit while Snape lurks around waiting for a dramatic moment to reveal himself. It turns out... well, not for the best given the entry immediately below but good enough for the series' plot, but the stupidity on display from four smart people and Harry and Ron is just mind-boggling.
- Pettigrew has been captured by the trio and two adults, and they need to escort him to the castle. They know full well that he's an Animagus who can turn himself into a rat.
You'd Expect: They'd use a simple Stunning Spell on him then float him to the castle, like they're doing to Snape at the exact same time. Or summon/conjure a jar, put him in it and make it unbreakable so he can't transform, just like Hermione does with Rita Skeeter's bug form in the fourth book.
Instead: They leave the murderer awake and chain him to two of them, one of who is about to turn into a werewolf. As soon as he does, the murderer transforms and falls out of his chains, leaving Ron chained to a hungry werewolf. But just before that happens...
You'd Expect: Hermione, or Sirius, who's currently carrying Snape's wand, to Stun Lupin, or magically restrain him in some other way as he's in mid-transformation (e.g. Hermione's full-body-bind curse).
Instead: Sirius shapeshifts into his dog form in order to fight Lupin off. He succeeds, but ends up in a great deal of pain, and nearly has And I Must Scream invoked on him by Dementors as a result.
- We learn in this book that the Wizard World has Time Turners, devices which can be used to actually travel back in time. Admittedly, they are limited in how far back they can go, but even a short distance would allow someone to get access to a huge amount of secret information or, if they were careful, actually interfere in the past.
You'd Expect: The devices to be kept under the strictest guard possible, for knowledge of them to be suppressed as much as possible and for them to only be used at times of the greatest need.
Instead: One was given to Hermione so she could attend more classes. While Hermione is more competent than most adults we see, they still ran a horrible risk the moment they made it available to her, if only because someone might have realized she had one and stolen it.
- The movie version has Sirius and Harry leave the group post-exposition, to stare at Hogwarts and have a talk about how Sirius is Harry's godfather and, with his name cleared, could return to being a free man and Harry could live with Sirius, finally free from his abusive aunt and uncle.
You'd Expect: The two of them to have this talk while walking out of the tunnel from the Whomping Willow (like in the book) and not leave the group, where the whole purpose was to get the alive-after-all Pettigrew to the castle, so as to prove Sirius' innocence, as soon as possible.
Instead: They waste time before the event of the clouds shifting, the moon becoming visible and Lupin turning into a werewolf, which ultimately gives Pettigrew a chance to escape, just because they needed a pretty backdrop to have the talk to!
- At the start of the book, Crookshanks is a lone Cat-Kneazle hybrid at the Diagon Alley menagerie, since no one wants him. He wins over Hermione, and attacks Ron while going for Scabbers, who is on the counter getting a checkup. The reason why Crookshanks is attacking is because he realizes that Scabbers isn't a rat, but an Animagus who is untrustworthy. Being a cat, however, he can't exactly communicate this.
You'd Expect: That Crookshanks would find some way to tell Hermione. Sirius mentions that Crookshanks was able to bring to him a list of passwords that Neville had written down, so Sirius could easily send a message via cat that the "rat is dangerous" or Crookshanks could maybe tell their head of House while she's in cat form.
Instead: Crookshanks keeps sneaking into the boys' dorm and attacking Scabbers at every opportunity, making Ron angry on Scabbers's behalf and suspicious at how the cat understands human speech. Eventually, when Crookshanks attacks Ron and Scabbers for the last time, even Hermione is trying to shoo her pet away because by then Scabbers has faked his death and framed the cat.
- Also, thanks to Crookshanks, Ron gets angry at Hermione for not taking the cat attacks seriously. He also points out that Crookshanks is Smarter Than You Look and seems to be gunning to eat Scabbers.
You'd Expect: Hermione to put a more active effort into keeping her cat away from Scabbers, or to figure out why Crookshanks seems to have a vendetta. This is straining her friendship with the boys and adding stress to her already-busy school year.
Instead: Hermione thinks that she can keep Crookshanks in her dorm, and refuses to take Ron's concerns seriously. This means that for most of the year Ron is yelling at her about Crookshanks, and Harry can't exactly defend her or Crookshanks. It finally gets to a head where Scabbers fakes his death by biting himself and leaving blood and cat hairs on Ron's bed sheets, which leaves Crookshanks as the perfect patsy. Hagrid has to call out Harry and Ron to lead to Ron and Hermione making up, after months of the three not talking.
Goblet of Fire
- After the madness of the Quidditch World Cup, riots and all, Ron and Harry come back to the Burrow to find that Mrs. Weasley has purchased dress robes in addition to their usual books and quills. Ron is furious that she's gotten him outdated maroon robes with lacy sleeves, while Harry feels guilty that he has gotten nice ones since Mrs. Weasley used money from his vault.
You'd think: Even though Ron has his pride, Harry at some point would buy him new dress robes that are in style, NOT maroon and much nicer, and give them anonymously. Alternatively, Ron could get over his pride and ask Harry for some money/new dress robes, or Mrs Weasley could just borrow some money from Harry and offer to pay him back later. That way when the special events come up, Ron won't look like a fool in his clothes.
Instead: No-one does any of the above, although Harry does buy lots of socks for Dobby as a present and at the end of the book asks Fred and George to buy Ron new dress robes on his behalf. As a result, Ron goes to the Yule Ball in those robes, and that's only the first of many catastrophes that ensue that evening.
- Despite Harry not applying for participation in the Triwizard Tournament, his name still comes up. The only explanation they have is that someone tampered with the Goblet of Fire, the device that selects participants, and planted the kid into the Tournament. However, when it is quite reasonably suggested that Harry should be excluded, the answer is that it's impossible because — as was mentioned before the start of the application period — those who are selected by the Goblet are entered into a magical contract and have to participate in the Tournament.
You'd Expect: That the precise details of this contract would be immediately made clear and any possible loopholes would be exploited. At the very least, Harry could do nothing and disqualify himself. Mind you, there are a lot of people who are unhappy with this development, starting from Harry himself and then to his friends and the supporters of the legitimate Hogwarts champion Cedric Diggory, and the delegations of the competing schools.
You'd Also Expect: That the adults who don't believe that Harry cheated his way into the tournament would try to find out the culprit.
Instead: Nobody does anything, and the fact that Harry's participation was orchestrated is completely ignored. There's no investigation, and even when the final task comes — so whatever the culprit's intention was this is their last chance to act upon it — no one is keeping an eye on the participants, and the villain has the free rein to rather blatantly interfere with the task and ensure the completion of his evil plan.
Moreover: The second and third tasks are a rather baffling moment for the entire school, because even setting aside the suspicious circumstances surrounding Harry's participation, somehow none of the hundreds of people present saw it as odd that during the grand events of the Tournament nobody gets to see the contestants.
- Hermione first learns of the Hogwarts house elves during this book. She isn't happy when she finds out that the elves work without pay, sick leave or pensions, and decides to set up the Society for the Promotion of Elfish Welfare (S.P.E.W.) to try and improve things for them.
You'd Expect: That if Hermione was serious about fighting for house elves' rights, she'd look for cases of elves who had genuinely suffered abuse and mistreatment from their masters and/or the ministry (e.g. Dobby, Hokey, Kreacher and the elves of the Black family, etc) and base her arguments around them. She did just that in the previous book when she was helping Hagrid to research for his defense of Buckbeak the Hippogriff.
You'd Also Expect: She would talk to the house elves and ask what they would want as a better lot in life. House elves run under Blue and Orange Morality where they prefer to work for witches and wizards, but they hate having abusive masters, or ones that dismiss them. It becomes a White Man's Burden if you want to speak for an oppressed group, and you don't bother to find out what the oppressed group wants.
You'd Also Expect: That she would chose a name for her crusade that doesn't sound so stupid and utterly impossible to respect.
Instead: She only uses the Hogwarts house elves as an example of why elves need rights for SPEW. Elves who, despite not being paid for their work, are quite content with their lot in life. As a result, no-one takes her case seriously.
In Addition: Thanks to Hermione's crusade, the Hogwarts house elves become disgusted with the Gryffindors. It starts when Hermione asks why they cover a drunk Winky with a blanket, instead of cheering her up for getting fired and then learning her master is ill. Then Hermione starts knitting hats, in the hopes of freeing the Hogwarts House elves, and Dobby reveals he pockets her hats because the other elves are insulted. It means he has to clean Gryffindor tower on his own, though he doesn't mind.
- Barty Crouch Jr. is using Polyjuice Potion to take the shape of Mad-Eye Moody, this year's Defense Against the Dark Arts teacher. In order to maintain his disguise he needs to drink a fresh dose every hour.
You'd Think: Since he already knows how long he has to stay at Hogwarts and can do basic arithmetic, he'd come prepared with all the doses he needs for the year squirreled away in his bottomless trunk or somewhere else.
Or At Least: If he runs short and needs a mid-year resupply, he'd simply contact one of his co-conspirators (such as Wormtail) outside the school and have them nip down to Knockturn Alley and buy him some.
Instead: He steals the ingredients necessary to brew a fresh batch from Snape's inventory of ingredient storage, despite the fact that this would be very likely to advertise to anyone who finds out that somebody is brewing Polyjuice Potion. The only thing that saves Crouch from having to duck a school-wide manhunt is Snape blaming Harry Potter for the theft because of both his hatred for the kid, and the fact that some of Harry's possessions coincidentally ended up near the scene of the crime.
- Harry figures out that for the second task of the Triwizard Tournament, he and the other three champions must find a way of breathing underwater for at least an hour, swim to the bottom of the Hogwarts lake, and retrieve something precious to them within an hour-long time limit. They are warned that should they fail to retrieve their object, it will be lost forever. Upon reaching the lake's bottom, Harry learns that the "precious things" are people the champions are close to.
You'd Expect: Harry figure out that the warning's just for show; none of the officials in charge of the Tournament would let any of the hostages die, given the safety measures that have been put in place for the Tournament, and the fact that all the hostages are actual people.
Instead: Harry takes the warning seriously, and after freeing his hostage, wastes time waiting for the other champions to show up and rescue their hostages, with the result that he nearly drowns, and ultimately finishes second-last after one of the other champions was eliminated early. Fortunately, Harry's determination to make sure all the hostages are saved is seen as him showing moral fibre, and he subsequently gets boosted to second place in the tournament ranking.
- As Sirius tells it, and Harry witnesses in the Pensieve, Barty Crouch's son was caught with a group of Death Eaters, the Lestranges, that captured and tortured the Longbottoms, leaving them legally insane. The crime causes scandal because the Longbottoms were popular, and Neville was the other potential Chosen One. The Longbottoms have no reliable testimony, and their son Neville is only a baby; on the other hand, the wizarding world wants a criminal to punish. Mrs. Crouch, who has a terminal illness, in particular is in hysterics about her son getting arrested, because he's their only child. Mr. Crouch fears the blow to his reputation.
You'd Expect: Crouch to do all that he could to verify his son's innocence or guilt. The Ministry has truth serum, Time Turners locked in the Department of Mysteries, and the means of extracting Crouch Jr's memories via Pensieve.
Instead: Crouch doesn't want to give the impression that he plays favorites. As Sirius tells it, Crouch Sr. grants his son a trial with a Kangaroo Court instead. Crouch Jr. spends the trial begging for his life and fighting the Dementors; his mother faints while watching the courtroom antics. While the Lestranges are definitely guilty, and the entire Wizengamot votes to send the Lestranges and Crouch Jr. to Azkaban for life, Crouch Sr. ends up destroying his reputation and chances of becoming Minister of Magic. People question about how the greatest fighter of Death Eaters could not realize his own child was going astray, and assume he practiced Parental Neglect. It doesn't help that as a last wish to his dying wife he smuggles her into Azkaban so that she switches places with her son; either way they both would have died, Crouch Jr. to the Dementors and Mrs. Crouch to her terminal illness. While it was unclear if Crouch Jr. was a Death Eater before Azkaban, when he comes out he definitely is. Crouch Jr. seizes the chance of freedom and helps bring Voldemort back to power. Nice Job Breaking It, Hero! doesn't begin to cover it.
- After Voldemort is resurrected, he, Harry and Death Eaters are all in a distant place, the only possible witness has been killed and Harry is trapped by a statue, completely at Voldemort's mercy.
You'd Expect: Once Voldemort was done gloating and summoning his Death Eaters he'd then kill Harry as quickly as possible. Likely with the knife used to resurrect him.
Instead: To prove to his followers that his failure to kill Harry 13 years ago was a fluke, Voldemort frees Harry and challenges him to a wizard duel. Granted, he couldn't have known that Priori Incantatem would occur, but Harry still ended up with plenty of leeway to escape without it. Harry is able to escape, and he warns Dumbledore and the world about Voldemort's return.
- Not long later, Minister for Magic Cornelius Fudge is informed of this turn of events. The evidence to support this includes the news coming from Albus Dumbledore, who isn't known for making stuff this serious up, and two testimonies. One of these is from a Death Eater who has admitted under truth serum that he has been in contact with Voldemort and working to ensure his return, and the other's from Harry, who claims to have seen firsthand the ceremony that restored Voldemort to full power, and has the injuries to show it. As well as this, Professor Snape shows him a very clear Dark Mark on his arm. The last time it was easily visible was during Voldemort's reign of terror. And, of course, Cedric Diggory's dead body.
You'd Expect: Fudge to figure out that with all this evidence supporting it, it's quite likely that Voldemort's back, and then take the actions suggested by Dumbledore to prevent him getting power and resources. Even if he doesn't believe it, he could still try and have the matter investigated, to confirm it for himself.
Instead: Not only does Fudge take no appropriate measures, he somehow gets it into his head that Dumbledore's making all this up to try and take Fudge's place as Minister - nevermind that Dumbledore has never wanted the Minister's post as far as Fudge has known him - all because he doesn't want to deal with Voldemort's return. The result of this is that during the next book, Voldemort's side is able to operate quite freely, recruit the giants to their cause and break out a load of their supporters from Azkaban, while Fudge does absolutely nothing useful. Thankfully, Voldemort doesn't choose to focus all his efforts on taking over, but if he had, the situation could have become a lot worse. And when the truth does get out, Fudge is fired.
Order of the Phoenix
- The Ministry believes that Dumbledore and Harry are involved in a common conspiracy to overthrow the government, faking Voldemort's return as part of their scheme.
You'd Expect: The Ministry would try to drive a wedge between Harry and Dumbledore, attempting to make a deal with Harry or otherwise counter Dumbledore's manipulations. After all, in Real Life, when an adult and a child are engaged in a common act of misbehavior, particularly when the adult is an authority figure, it is generally accepted that the adult bears the brunt of the blame.
Instead: The Ministry blames Harry and Dumbledore equally. Umbridge in particular goes out of her way to antagonize Harry with sadistic detentions and an obviously personal vendetta, ensuring Harry's continued support of Dumbledore.
- Voldemort is trying to lure Harry to the Ministry of Magic in order to retrieve a Prophecy about the two of them. His strategy is to use Legilimency to make Harry dream about the place, and want to explore it in person. Dumbledore realises this, and also figures out that Harry and Voldemort have a mental connection that Voldemort could use to spy on Dumbledore through Harry. In response to all of this, Dumbledore arranges to have Harry learn Occlumency, so that he can stop having these dreams.
You'd Expect: Dumbledore to just tell Harry about the mental connection, the Prophecy and Voldemort's plans for retrieving it, and explain that this is why he has to learn Occlumency. That way, Harry might be more motivated to do so. Hell, Dumbledore had decided at the end of book four that the time was right to tell Harry about the prophecy.
Instead: No-one tells Harry anything other than "you MUST learn Occlumency", "Voldemort might be able to read your mind, but not while you're at Hogwarts" and "There is nothing in the Department of Mysteries that concerns you". As a result, Harry doesn't take the lessons as seriously as the Order would like him to, remains curious about the Department of Mysteries related dreams he keeps having, and is surprised when the Order consider it a big deal that Snape's no longer teaching him.
- Dumbledore's choice of Occlumency teacher also counts, as he admits at the end of the book.
You'd Expect: Dumbledore to either teach Harry himself, or try and find someone else to do the job. Moody's a possible example; with his level of paranoia about everything, it's hard to imagine him not learning Occlumency to protect his secrets. For that matter, since Draco Malfoy proves its possible for a talented student to learn Occlumency over the course of one summer if he has a competent teacher and the decision that Harry needs to learn Occlumency isn't made until mid-term, Dumbledore has enough time to train literally anyone else in the Order of the Phoenix to be an Occlumens from scratch, and still have them finish teaching Harry before end-of-term.
Instead: He gets Professor Snape to try and teach Harry Occlumency, a magical art that is based on controlling your emotions, when the two of them have a longstanding mutual hatred and visibly cannot so much as be in the same room without enraging each other by their very presence. Unsurprisingly, this crashes and burns.
To Be Fair: The political climate likely meant that any meetings between Dumbledore and Harry would be viewed with suspicion. While Snape was not an ideal choice, he was, in some ways, a safer choice.
- Ron becomes the keeper for the Gryffindor Quidditch Team, of which his brothers Fred and George are also members. It soon becomes apparent that Ron has huge confidence issues on the pitch, which greatly affect his ability to play.
You'd Expect: Fred and George would try and give Ron some form of emotional support, if only because their chances of winning the Quidditch Cup are somewhat dependent on their brother's performance as a keeper. They're certainly capable of doing this, judging from their attempts to cheer up Harry the first time he failed to win a Quidditch game.
Instead: They initially choose to make fun of Ron for being a prefect, and do absolutely nothing to help him get over his Quidditch insecurities. It gets to the point that after Fred and George leave Hogwarts, Ron's performance drastically improves in their absence.
- Since the beginning of the year the Ministry of Magic has been steadily antagonising Harry and DD, painting the kid as a liar and a madman in media and staunchly refusing to accept Voldemort's return. Then a Ministry official, Dolores Umbridge, is appointed the DADA teacher at Hogwarts, and at her first lesson she makes it perfectly clear that she's upholding this policy and assures children that "there's nothing dangerous out there" and they don't need to practice defence magic.
You'd Expect: After this first lesson at the least, Harry would try to keep his mouth shut, since, frankly speaking, he has no proof of Voldemort's return, and won't achieve anything by proclaming it again.
Or: He could've countered Umbridge's assurances by mentioning Sirius. After all, the Ministry couldn't deny his existence, and they did fail to capture him, so they couldn't deny he was a threat either.
Instead: He tries to claim that Voldemort has returned, with no proof other than his word. He doesn't convince anyone and ends up with a week of detentions.
- During said detentions, Umbridge forces Harry to magically carve the words "I must not tell lies" into the back of his hand.
You'd Expect: Harry to inform Professor McGonagall and/or Dumbledore and, for his next detention, take one of them (or anybody else) with him under the Invisibility Cloak. You'd think the Ministry, even in its newfound Jerkass mode, would hardly be able to get away with mutilating children.
Instead: He suffers silently, not wanting to give Umbridge the satisfaction of seeing him complain and not wanting to talk to Dumbledore due to being angry at him for keeping Harry in the dark, and lets her continue her reign unchallenged.
- Cho Chang decides to join the illegal defense group Harry had set up under Professor Umbridge's nose. She also has a friend called Marietta Edgecombe, whose mother works at the Ministry of Magic, and would therefore be likely to lose her job if her daughter got on the wrong side of Umbridge.
You'd Expect: Cho to either keep Marietta in the dark about the group, or tell her about it, but not put her under any pressure to join.
Instead: She makes Marietta come to the meeting with her (her words), effectively lumping her with the group whether she likes it or not. Things are all well and dandy for about six months, but then Marietta reports the group to Umbridge, and Dumbledore is forced to take the blame for it to protect all the students involved. Marietta meanwhile is left disfigured, and viewed as a traitor, as a result of her "betrayal", whereas Cho - who was technically responsible for all of this - faces absolutely no consequences as a result of her actions.
- There's also the matter of Hermione's security measures. She's capable of enchanting the signing-up sheet so that if anyone breaks their oath of silence, a spell is cast.
You'd Expect: She would install an alarm system so that if anyone talks, everyone else is warned. Or she'd use a Tongue-Tying Curse or Silencio or something similar to shut people up before they can say too much. You'd also expect, both so it could actually deter betrayal and just on ethical grounds, she'd warn the members about this security measure.
Instead: She curses any betrayer with facial disfigurement spelling out the word "Sneak", which only takes effect after they've told someone about the group. Marietta is able to tell Umbridge everything and only afterwards does she realise she's been cursed in this particularly vindictive fashion (it's still there the next year!).
- Adding onto this is the betrayal. Marietta knows that Umbridge threatens to expel anyone who breaks her Educational Decress, and it's weighted against the houses so that Ravenclaw would get no second chances.
You'd Expect: Marietta to realize that this means Cho would get expelled for participating in the DA and keep her mouth shut. Cho has already suffered a massive trauma from losing her boyfriend to Voldemort, and being expelled would isolate her further.
Instead: Marietta rats out everyone in the DA, including her best friend. While Cho forgives Marietta, in part because Marietta was the only friend who stayed with her after Cedric died, it makes Marietta a pariah and known as the student that sold out Dumbledore to Umbridge. It also means that Harry and Cho break up before they can even start a relationship, because Harry points out this particular fact to Cho.
- Harry gets given a package from his godfather, who implies that Harry can use it to keep in contact with him while he's at Hogwarts.
You'd Expect: That Harry would at least have a look at the package, to see what it is, even if he doesn't plan on using it.
Instead: He doesn't, apparently afraid that if he so much as opens it, his godfather will get in trouble. It turns out to just be a magical equivalent of a walkie-talkie.
Result: Whenever he wants to talk to his godfather, he has to break into Umbridge's office.
You'd Also Expect: That the first time Harry did this, Sirius would tell him to use the mirror, so that they can talk safely in the future.
Instead: Sirius never gets round to it. Granted, he wasn't alone with Harry during the conversation, and he may have had his reasons for not wanting his oldest friend Lupin in on the secret of the mirror. But you'd think he could at least have said, "Remus, I'd like a private word with my godson, if you don't mind."
You'd Also Expect: That the Order in general would take care of providing Harry with means of emergency communication, not to mention extraction. They know that the boy is a trouble magnet, and that the enemy is after his head. Especially since Harry knows how to cast a Patronus and that's a foolproof message system. All they had to do was teach him that and the entire climax of Book 5 could have been avoided
Instead: Nobody gives a damn, except Sirius, and he's so conflicted and guilt-tripped by everyone for being possessive of Harry, that he ends up being Master of the Mixed Message, and of course it leads to a disaster.
- Professor Umbridge gets Snape to give her some truth potion, which she plans to use to interrogate Harry on the location of two of his most important people, both of whom are fugitives. Snape, who is a renowned expert in the field of potions, tells Umbridge that she only needs to use three drops of the stuff for it to work.
You'd Expect: Umbridge to remember this when the time comes to do the deed, especially since Snape is a potions expert and she is not.
Instead: She uses up the whole bottle. Worse, it's Snape's last sample of that potion (so he says, anyway), and it takes a month to make. The result is that the next time she needs it, naturally there's not a drop in the castle.
And On Top Of That: She not only pours the whole bottle into Harry's drink, she then fails to make sure that Harry actually drinks it. Harry defeats her by the simple ruse of raising his cup to his lips but not actually opening his mouth, and Umbridge — despite looking directly at him the entire time — unaccountably fails to notice that Harry is not swallowing anything, and that Harry's robes are stained from where he spilled some of the tea on himself to lower the liquid level in his cup.
You'd also expect: Umbridge, who's a government veteran, to be able to dissemble convincingly in front of a teenage boy, even one who's already suspicious of her.
Instead: She acts in a manner that practically screams "I have given you that drink for nefarious purposes."
- Hermione and Harry manage to lure Umbridge into the Forbidden Forest by claiming that Dumbledore is keeping a weapon hidden there. The trio are then confronted by the resident herd of centaurs, who generally don't take kindly to wizards intruding in their territory.
You'd Expect: Umbridge to decide that staying alive is far more important than fulfilling her Fantastic Racism quota for the week, and not do anything to provoke the centaurs.
Instead: In a supreme display of being Too Dumb to Live, she repeatedly insults and tries to boss around the huge herd of centaurs surrounding her. The herd promptly drag her off into the forest, and while we don't see what happened to her after that, it was rough enough to give her PTSD.
- Right after the above scene, the centaurs are deciding what to do with Harry and Hermione. One of them points out that they bought Umbridge here, and that Harry is nearly an adult, implying that they won't have to worry about breaking their rule of not hurting children.
You'd Expect: Hermione, who is typically very knowledgeable about the wizarding world in general, to remember that a major Berserk Button for centaurs is the idea of serving wizards, and therefore say something along the lines of "We were trying to find the giant, so he could get rid of Umbridge. We never meant to run into you guys!".
Instead: She straight-up tells them that she was hoping they would deal with Umbridge for her. The centaurs, furious at being used, decide that Harry and Hermione can share Umbridge's fate, and the pair are only saved thanks to Grawp randomly showing up.
- Voldemort lures Harry to the Ministry of Magic and sends his goons there to retrieve the important Prophecy that only Harry can touch.
You'd expect: Lucius Malfoy, who's in charge of the operation, would only take those Death Eaters who, like him, had weaseled their way out of Azkaban and into the Ministry ranks, and thus would have a legitimate excuse to be there (or send only the escapees). When the kids arrive, ambush them right in the atrium, disarm, and take hostage. Walk the now cooperative Harry straight to the storage and make him take the Prophecy orb.
Instead: He takes the recent escapees from Azkaban with him, so when the Cavalry arrives, his true allegiances are exposed. They then waste time in the storage, waiting for Harry to come to them and stumble upon the prophecy, and only reveal themselves after Harry takes the orb, and they can no longer shoot him with spells for the fear of breaking it.
- During the events at the Ministry, we see that the Time Turners are kept on an open shelf, without any locks, guards or alarms and in a room accessible to a bunch of kids. The power to rewrite the timeline is there for the taking.
You'd Expect: That of the numerous people who infiltrated the Ministery that night, someone, be it heroes or villains, would realise the tremendous potential and help themselves to a Turner or two.
Instead: They are completely ignored. In fact, all of the Time Turners are destroyed by a missed Stunning Spell from Neville and fall into a consistent loop of falling, shattering and repairing themselves.
- The prophecy ball Voldemort wants is kept in the Department of Mysteries in the Ministry of Magic. It can only be obtained by himself, or Harry Potter.
You'd Expect: That Voldemort would simply sneak in and steal it, seeing as Harry and 5 other kids practically waltzed in there undetected, despite the fact that Harry is high on the list of people the Ministry is against at the time. It's not like he cannot disguise himself, up to turning invisible, or murder any possible witnesses.
Instead: Voldemort decides that it is too dangerous to attempt this as he will probably be discovered and the world will know he is alive again. Naturally, Voldemort tricks Harry into stealing the prophecy. Then the Death Eaters try to steal it from him before he escapes. And then Voldemort, who claimed it was too dangerous for him to enter the Ministry, enters the Ministry, just after the prophecy gets destroyed, without a disguise, revealing himself and making his plan less than useless.
- Voldemort, demoralised by his failure to kill Harry at the end of the previous book, is both working in secret to build up his power and trying to get his hands on the prophecy stored in the Ministry of Magic. Fortunately for him, his henchman Lucius Malfoy is very politically influential and is evidently on close terms with Cornelius Fudge, Minister of Magic.
You'd Expect: Voldemort to realise what he does in book 7, that the Imperius Curse exists, and simply put Fudge under mind-control. Either have Lucius do it - Fudge is easily influenced even by non-magical means and doesn't seem like the kind of person who could out-draw Lucius - or have Lucius invite Fudge to his house on some pretext (again, Fudge is easily influenced and is on close terms with Lucius) where Voldemort can ambush him and place him under Imperius himself. Even if Fudge couldn't bypass the protections in the Hall of Prophecy, at least Voldemort would control the head of government of Wizarding Britain.
Instead: He doesn't. It takes until Deathly Hallows for him to realise that highly-placed government officials can be made his slaves with a single spell.
- Sirius is under an imposed house arrest for most of the duration of this book.
You'd Expect: For Dumbledore to use his considerable influence to take steps to prove Sirius's innocence, via obtaining a fair trial, questioning under Veritaserum, or reviewing Sirius memories via a pensive. If this fails, then he could at least provide a stay of execution under the guise of Sirius being an informant a la Snape, at least until Pettigrew could be potentially apprehended. This would also be an added bonus of being a good faith gesture towards Harry, who is already anxious and stressed over the year's events and the Professor's distant demeanor for albeit, good, if misguided reasons, and for Sirius, in clearing his name.
Instead: Neither Dumbledore, nor anybody else, thinks of this, and Sirius, through a series of events, dies without clearing his name. He then gets acquitted postmortem, as Cornelius Fudge mentions at the beginning of book six when it does no one any good.
You Also Expect: That since Sirius has proven capable and competent escaping Azkaban entirely on his own and being on the lam for most of Book 3 and Book 4, that Dumbledore and the Order stop irritating and condescending to him, and also trust him with some small missions with low-risk since it doesn't do to keep a strong wizard like him entirely out of field.
Instead: They more or less aggravate Sirius for being useless, give him a huge chip on his shoulder and when the moment comes for them to fight and Harry is in danger, he rushes in and out of lack of preparation in the field, he oversteps himself and falls in battle, with the Order losing one of their best wizards.
- After Sirius dies, Dumbledore admits it was very stupid of him to have Snape teach Harry Occlumency. He reveals he could have taught him easily, with far better results.
You'd Expect: He would restart the lessons, this time being the teacher, and reprimand Snape off-screen for royally screwing up. While Harry was at fault for looking into the Pensieve, Snape's reaction —kicking Harry out and prematurely ending the lessons— did not help. Harry in fact points this out.
Instead: Dumbledore doesn't do either of these things in the next book; his main priority with Harry is to educate him about Voldemort. Snape is a Karma Houdini for his failure to teach Harry, and keeps angrily insisting that he demands more answers as to Dumbledore's plan. As a result, Harry never learns to block his mind, and Snape's Jerkass attitude leads everyone to believe Dumbledore fooled him when the former kills the latter.
- Regarding the above, at the start of each Occlumency lesson, Snape places certain memories in a Pensieve, so that if Harry's attempts to defend himself against Snape's Legilimency (or if Voldemort picks that moment to enter Harry's mind and use Legilimency on Snape), those memories won't be available. Harry knows Snape is spying on Voldemort for Dumbledore, and at this point in the series seems to agree with Dumbledore's trust of Snape.
You'd Expect: Harry not look in the Pensieve. It's an easily-avoidable breach of privacy in itself, but the idiocy comes in when you realise a) Harry knows Snape is spying on Voldemort; b) Voldemort is a powerful Legilimens; c) the whole point of these lessons is that he needs to stop Voldemort entering his mind; and d) he hasn't been practicing like Snape told him, because he really wants to know the secret Voldemort is telepathically dangling in front of him. All this means that anything Harry sees, Voldemort might see, and Harry even considers that Snape might be hiding important secrets of the Order of the Phoenix in the Pensieve. Again, ethics and practicality are at one in this: Harry should not look in the Pensieve.
Instead: Harry looks in the Pensieve. Specifically hoping he'll find information on the thing the Order is trying to keep safe from Voldemort. Fortunately, Voldemort isn't looking through Harry's eyes at the time, and Harry randomly gets a memory of one of the things Snape regrets the most, but when Snape comes back from dealing with a student-related emergency and finds Harry with his face in such a personal memory, he's understandably furious, throws Harry out, and ends the lessons.
You Also Expect: Snape knowing that Harry's not engaging in Occlumency lessons, and that he has a history for being nosy and being overly curious, would not ostentatiously pour his memories in the Pensieve in front of Harry (showing him that he's hiding something) or alternatively put the memories in a phial like how Dumbledore collects memories and keep it under his bed or in a pocket inside his cloak. This is in keeping with both his opinion of Harry's character and likewise representative of his own position as a spy and Potions expert, and his secretive nature.
Instead: He pours memories in the Pensieve in front of Harry, leaves the room with the Pensieve container open with all his memories still floating inside. This after taunting Harry by lording over his knowledge and position in the Order, interspersed with insults to him and his family, which naturally is only going to make Harry respect him and his privacy and position even less than before.
- So Rufus Scrimgeour has taken over the Ministry in the wake of Cornelius Fudge's disgraceful resignation. Lord Voldemort is back and causing havoc to Muggles, and Harry, previous vilified, is now known as "The Chosen One."
You'd Expect: That Scrimgeour would do damage control in regards to Fudge's bizarre and terrible last year in office, first by doing research as to how terrible the year went and then getting rid of people like Umbridge, who had a pretty upsetting regime at Hogwarts and was openly trying to get Harry expelled. In addition, Scrimgeour would actually listen to Harry when trying to recruit him as the Ministry's poster boy to boost morale since the kid has survived Voldemort at least four times and is Wise Beyond Their Years.
Instead: Scrimgeour does none of this. Umbridge, as he foolishly mentions to Harry, is not only STILL in the Ministry, but also passed along the information that Harry wants to be an Auror after insisting that he would never become one. He also doesn't bat an eye when Harry shows him the quill scars Umbridge gave him, even though that's physical evidence of abuse. Harry points out that arresting someone like Stan Shunpike invokes He Who Fights Monsters the way Mr. Crouch did, and Scrimgeour dismisses him. All in all, the real question is just how he expected Harry to forgive the Ministry after the events of Year Five and not even making a token apology.
In Addition: Umbridge is a Karma Houdini in regards to her mutilating underage teenagers at Hogwarts, if one discounts whatever the centaurs did to her. She has no loyalty to the Ministry and is sadistic for the fun of it.
- Harry suspects Draco is a Death Eater and tries to warn others.
You'd Expect: That they would take the idea seriously. After all, Harry himself is proof that you do not have to be an adult to make significant accomplishments. Additionally, in the Muggle world, terrorists, criminals, and other irresponsible people use kids to do their dirty work all the time; just give them goodies, fill their heads with nonsense about adventure and glory, and give them a mission that does not require too much intelligence and where it doesn't matter whether they come back alive.
Instead: Harry's concerns are dismissed out of hand, based on the idea that Draco's just a kid. Dumbledore is one thing, since he's trying to help Draco from getting his soul split, but the others have no excuse.
You'd Expect: Harry would at least try to check if Malfoy has the Dark Mark. Which should be as easy as ambushing him somewhere, while under the Invisibility Cloak, stunning him, and rolling up his sleeve.
Instead: He never even entertains this idea, continuing to press his point without any proof and getting dismissed again.
- Later Harry deduces that Malfoy is busy with something in the Room of Requirements and wants to find out what. The Room appears and opens when you tell it what you need it to become. Harry tries to ask it to "Become what you became for Draco Malfoy", but it doesn't work.
You'd Expect: That he would try a different approach, such as replicating Malfoy's request, at least in general terms. As later inadvertently revealed by Professor Trelawny, it was as simple as "I need a place to hide something".
Instead: He, metaphorically, keeps banging his head on the wall, trying every possible variation of his initial meta-request, even though it clearly doesn't work, and the reader can only follow suit.
- In Order of the Phoenix, Harry failed to listen to the advice of someone who was not only a good friend, but the most intelligent of his friends. When Hermione repeatedly told him that there must have been a good reason for Dumbledore to want him to learn Occlumency, and later, that his vision of Sirius being tortured was probably a trap, he angrily brushed her off, and his refusal to listen to reason ultimately culminated in his godfather getting killed and most of his friends ending up hospitalized.
You'd Expect: That in the future Harry would at least give some serious consideration to the advice of a friend who could have saved him a whole lot of grief if only he'd listened to her from the beginning.
Instead: He continued to brush her off when she repeatedly warned him about the fishiness of the so-called Half-Blood Prince's book, deciding that an easy Potions grade was worth more to him than the concerns of one of his closest friends.
- Said book contains a number of obscure hand-written spells lacking any kind of explanatory notes as to their purpose or effect.
You'd Expect: That a person, who'd been studying magic for six years and had more then once witnessed firsthand how dangerous and unpredictable it can be, would know better than to wantonly use unknown spells.
Instead: Harry tries one of them in their own dormitory. Luckily, it turns out to be a type of levitation spell that yanks a person by an ankle and hangs them in the air, but otherwise does no serious harm.
Even Worse: He just flicks his wand randomly, not even looking at what he was aiming at. If that had been Sectumsempra, Ron could've died right there and then.
You'd Expect: Harry to take the hint and start treating the book with caution it clearly deserves.
Instead: He casts another spell, labeled only as "for enemies", during a fight with Malfoy. It turns out to be a vivisection spell, and he very nearly kills Draco.
You'd Expect: Harry to really take the hint and either destroy the book or surrender it to the teachers. It's not like he could've gotten into any more troubles than he already was in, and giving up the book could even be counted in his favor and alleviate his sentence.
Instead: He hides the book, apparently intending to retrieve it once things calm down. Thankfully, he never gets the chance, and later one of the villains inadvertently burns the damn thing before any more damage could be done.
- In this book we find out about Voldemort's set of six Soul Jars keeping him immortal.
You'd Expect: He'd make them impossible to discover either by using nondescript objects that wouldn't stand out to someone or by hiding them in places only he knows about, that are unconnected to him in his history.
In Addition: Since you don't actually have to have a Horcrux available to hand in order to use it to resurrect yourself, you don't have to worry about keeping it somewhere you can fetch it back from. So absolutely nothing prevents Voldemort from doing something like sealing at least one backup Horcrux into a 55-gallon drum of cement and then dumping it overboard at a random spot in the ocean. Or launch it into space.
Instead: He uses rare and impressive artifacts and hides them in places connected personally to him, most notably, at Hogwarts, where most of his enemies have been for the past 6 books. And while Voldemort does do his best to hide the connections between him and the artifacts, he ultimately fails, with the heroes practically knowing his whole backstory by the end of the book.
Also: Because Pride is a Fatal Flaw of his, he hides them all in places that are entirely possible to walk to, with at most a few traps or guards between the Horcrux and the exit, assuming that no-one could possibly discover a secret of Lord Voldemort.
- During Harry's lessons with Dumbledore, Dumbledore shows Harry a memory of Slughorn talking with the young Voldemort about "Horcruxes" and tells Harry that he believes the memory to have been tampered with and that it's important to get the real memory.
You'd Expect: Dumbledore would tell Harry what a Horcrux is and why he thinks it's so important to get the contents of this conversation, particularly since he had previously promised to tell Harry everything he knew or even suspected about Voldemort's actions and plans.
Instead: He doesn't tell Harry anything other than to get the memory, Harry doesn't place a very high priority on it, and several months are wasted.
- Harry and Dumbledore infiltrate the vault where Voldemort's Horcrux is kept. The thing is lying at the bottom of a basin full of potion that cannot be removed by any means, other than drinking it. When Harry quite reasonably notices that drinking the potion's a stupid idea, because it's a potion made by Voldemort, Dumbledore reassures him that V would want to interrogate the intruder, so while the potion would most likely cause pain, weakness and other debuffs, it would not be lethal. He also insists that he (Dumbledore) has to be the one to drink it, because "he's much less important than Harry".
You'd Expect: Harry would then just as reasonably notice that it's a tremendously stupid idea, because if Dumbledore is right, then there must also be an alarm to inform Voldemort about the intrusion, and he's either on his way to the cave or already there, waiting outside for DD to drink and keel over. Or at least there might be other wards installed to finish off the weakened thief. Obviously, in such situation it's a suicide to let Dumbledore drink the potion.
Instead: He just goes along with it and only survives because of the point below.
You'd Expect: The cave defense to actually work this way. There either should have been an alarm, or the potion should have been lethal. Or perhaps both.
Instead: The potion causes a terrible thirst in the victim, wards prevent water from being conjured, forcing the victim to drink from the surrounding lake, which causes a horde of Inferi to rise up and drown the thief. Except that it doesn't work if the thief uses someone else to drink the potion and then simply prevents them from going for the water. You cannot even argue that Voldemort overlooked this possibility, because that was exactly how he tested the potion - by having someone else drink it. And since there's no alarms, nothing prevents the thief from leaving and returning with the spare. And the Inferi prove to be rather crappy guards, as Dumbledore, even in his weakened state, manages to fend them off. It also ignores the possibility of a thief coming, noticing the no-water-conjuration ward, leaving and coming back with a water supply, bypassing the ward. While they may not realize there are Inferi, the fact that there is a ward to stop water conjuration indicates that they will want water. And given that there are curse-breakers who regularly break into warded and cursed tombs, the possibility of someone having the relevant skills is there. In canon, Dumbledore winds up with two known Curse-Breakers; Bill and Fleur. How many others did he have, and how many did he have in the first War that Voldemort should have considered?
What makes all of this worse is that someone before Harry and his mentor did figure out the loopholes and stole the Horcrux long ago, leaving an identical-but-inoffensive replica in its place. This person was Regulus Arcturus Black, abbreviated R.A.B., who left a letter inside the fake object so Voldemort could read it and know that his secret was discovered. Indeed, Voldemort's stupidity rendered not only his own efforts to protect the Horcrux in vain, but also Harry's and Dumbledore's to retrieve it in the first place, thus requiring the difficult events of the first half of Deathly Hallows to locate and destroy the real thing.
- We learn that in the distant past, Albus Dumbledore's sister Ariana had been attacked by three muggle boys who'd seen her doing magic, with the resulting trauma leaving her unable to control her magical abilities. The rest of the family - Albus, his brother Aberforth and his mother Kendra - assume that the Ministry of Magic will send Ariana to St. Mungo's for the rest of her life, should they ever find out about her, out of fear that she would break the International Statue of Secrecy with her inability to control her magic. To get around this, they decide to keep Ariana's existence a secret from the entire world, to the point that they barely let her out of the house.
You'd Expect: That after a few months of this treatment, the Dumbledores would realise thay what they're doing to Ariana isn't much different from what they fear the Ministry will do, and commit her to St. Mungo's. It's not as though this would spell (pun not intended) doom for Ariana: St. Mungo's is shown to have the means to take care of people like her, and the place also allows family members to visit patients, so it's not as though the rest of the family will never see Ariana again. In any case, it would probably prevent a lot of the stuff below from happening.
Instead: The Dumbledores continue to hide Ariana from everyone, and it causes the family nothing but trouble. First, Kendra gets killed in one of Ariana's outbursts, leaving Albus to look after her, a situation that he very much resents. Then Grindlewald shows up, and his friendship with Albus and their plans for the future threaten to leave Ariana on the proverbial kerb. Aberforth's attempts to stop this from happening lead to a fight between the three wizards in which Ariana inadvertedly gets killed long before her time.
There's more: Ariana's death creates a rift between the remaining Dumbledores, with Aberforth blaming Albus for killing their sister. The event also leaves Albus reluctant to confront Grindlewald when his former friend turns bad, out of fear that he'll be revealed as the one who killed Ariana, leading to the deaths of many people before he gets his act together. Finally, the whole thing becomes a stain on the Dumbledore family's history in the present day, with people assuming, based on what little they can find out about Ariana, that she was abused, imprisoned and murdered for not having magical abilities.
- We find out that R. A. B. is ex-Death Eater Regulus Arcturus Black was the man who unearthed the secret of Voldemort's immortality and replaced the Horcrux Locket via Heel–Face Turn.
You'd Expect: For him to try and contact people in the Order, such as Dumbledore, Sirius or someone who might use this valuable intelligence, protect him, and also be able to destroy that magical device.
Instead: He tells his house-elf Kreacher to destroy it even if the latter has no idea, is magically bound by oaths not to relate that information to anyone else, performs a Stupid Sacrifice, and more or less leads to deaths over twenty plus years that could have been avoided or reduced had he not been as his brother Sirius called him, "a little idiot".
- Harry, Ron and Hermione learn that one of Voldemort's Horcruxes (the one that should have been in the cave explored near the end of Half-Blood Prince) is in the possession of Dolores Umbridge, and make plans to infiltrate the Ministry of Magic, now controlled by Voldemort, in order to steal it.
You'd Expect: The trio, in addition to figuring out how to enter the Ministry in the first place, would come up with ideas on how to go about finding the Horcrux, how to move around the Ministry without arousing suspicion or being sidetracked, and perhaps most importantly, how they can escape.
Alternatively: One of the trio could go in under the invisibility cloak and find out where Umbridge's office is, and then he or she could just wait there until Umbridge returns, take her out, and steal the locket.
Or even: They could find out where she lives, which couldn't possibly be as secure as the Ministry of Freakin' Magic, and either waylay her outside her house or wait for her to go to sleep, break in, and take the dratted thing.
Instead: Harry and co. plan their method of entering the Ministry...and that's the extent of their preparation. They don't think about anything else, and it bites them in the ass twice; Hermione and Ron are sidelined for the duration of the mission when their disguises lead the two of them to be mistaken for Ministry employees and given jobs to do, and the trio's hiding place is compromised during their escape attempt. This forces the trio to hide out in the wild, which, coupled with both the Horcrux's corrupting effects and frustration on the lack of information Dumbledore gave Harry regarding the Horcruxes, leads Ron to ditch the other two.
- Following the above, the heroes are living out of a tent, running low on supplies, have very limited access to research materials, and having to move frequently to avoid being found by Death Eater search parties.
You'd Expect: They would remember that Voldemort's people only have freedom of movement within the United Kingdom as that is the only government Voldemort controls at this moment, and that there is no reason they have to stay in the country, just merely to visit it whenever they think they've found a Horcrux location. And simply relocating to France would allow them a safer territory to stay in, access to sources of supply, possible allies (such as Fleur's parents or Madame Maxine), and much greater access to research materials (such as the library of Beauxbatons). As to how they could get there? Wizards are demonstrably capable of Apparating from northern Scotland to London in a single jump, which is enough distance that you could hit Germany in a single jump from London, let alone France. Alternately, people who can turn invisible, shapeshift, teleport around security barriers, and rewrite memories don't have much trouble getting through Customs.
What's Worse: Hermione's family takes vacations in France, the most recently being three years ago right before the Tri-Wizard Tournament. And it's specifically lampshaded in the text that one of the reasons the Trio was able to use the Forest of Dean was because since Hermione had vacationed there when she was a small child, she remembered the place well enough to use as an Apparition destination! And yet she can't remember a place she's been to far more recently, because it would be inconvenient for the script if she did. Bleah.
Or At Least: Hermione would remember that the muggle world is full of places where you can buy food — or, if you're worried about leaving a trail, you can use your magical wizard powers to steal food from after hours. Again, its not like people who can turn invisible, teleport, and trivially open any non-magical lock are short of options, and the Trio had already shown a willingness to 'midnight requisition' food from isolated henhouses and suchlike.
Instead: The Trio consistently act like the United Kingdom is the only nation on the entire planet and never even idly ponder the idea of operating from a base area beyond Voldemort's span of control, despite easily being able to reach one. Likewise it is literally months before Hermione thinks to buy more food at a grocery, and even that only for a special occasion instead of as a regular occurrence.
- After stealing the Locket Horcrux, Harry wears it for safekeeping. As a result, he becomes terse and cold with Ron and Hermione and can't produce a Patronus when he encounters Dementors. After taking it off, he is much better.
You'd Expect: Harry to keep the Locket in his mokeskin pouch, where no one but the pouch's owner can get it out, or Hermione to keep it in her beaded bag. It may be hard to find in the beaded bag, but at least they're not interacting with it in a way that would activate the horcrux (Ginny writing in the diary and Dumbledore putting on the Ring Horcrux; Ginny was possessed by the fragment of soul in the diary and Dumbledore was given mortal wounds by putting on the Ring).
Instead: Harry insists they wear it. As a result, tensions grow between the trio until Ron leaves for several months. On top of that, the Locket tries to kill Harry twice while he's wearing it.
- Voldemort finds out that his wand and Harry's have identical cores, causing them to malfunction when used against each other.
You'd Expect: Voldemort to let someone else kill Harry. It's too dangerous to risk going wand-to-wand against Harry personally when all it does is reflect your spells and cause Harry's own wand to become more powerful.
Or: Voldemort to be a little more creative in his spell usage. The man is one of the most talented wizards alive, and has demonstrated several spells that would not require him to use a direct magical attack. In his fight with Dumbledore alone, he conjures a giant flaming snake and turns a room full of glass into a deadly Flechette Storm.
Instead: Voldemort insists HE must kill Harry and keeps trying the Killing Curse to no effect. He wastes time on futile schemes to find a loophole, such as using another servant's wand or searching for the Elder Wand. So Harry survives. Again. And again. And again.
- Harry accidentally summons a load of bad guys by saying Voldemort's name, despite having been previously warned that it had been jinxed and shouldn't be spoken out loud and having even been reminded of it right before he said it. The bad guys appear, and aim their wands at the heroes' tent.
You'd Expect: They would first try side-along apparating to a short distance away from the tent and the bad guys. They've got the hang of it by now, and they've used it to get out of a number of similar situations. For bonus points, they could then sneak up on the bad guys, stun them and leave. Lacking that, Ron and Hermione could've gone out and distracted the baddies, while Harry sneaks out under the invisibility cloak and then snipe them all.
Instead: Hermione uses a spell to disfigure Harry's face, to prevent the bad guys from identifying him as such, and they try to talk themselves out of the situation. They fail, thanks to the fact that one of the Snatchers sees Harry's scar on his forehead.
- Following from the above, the Snatchers take the trio to Malfoy Manor to be rewarded by Voldemort in person. Before the Malfoys can summon Voldemort, Bellatrix notices they have the Sword of Gryffindor, which is supposed to be in her vault, and freaks out. Since the vault also stores one of the Horcruxes, she is afraid they might have sneaked in and stolen it and intents to find out.
You'd Think: That even the freaked out Bella would see the very simple solutions of either making a quick trip to Gringotts and checking on the Horcrux, or using Legilimency to check the trio's memories to find out where they got the sword.
Instead: She decides to brutally interrogate Hermione with the Cruciatus Curse (and in the movie adaptation, carve "Mudblood" on her arm), even though in a world where memory charms exist, its inefficiency for interrogation should be obvious to anyone.
Additionally, You'd Also Think: Knowing full well that in the wizard world even the most innocuous tackle can be a magical artifact of unknown power, the villains would strip their prisoners of all possessions, down to the clothes.
Instead: They content themselves with taking away the boys' wands. Naturally the boys have some spare artifacts that help them escape, including the mirror shard.
- Griphook demands the sword of Godric Gryffindor as payment for helping them break into Gringotts. Harry is willing to give it to him but only after destroying the Horcruxes with it. Harry also knows that, thanks to whatever powerful enchantments that were placed on the blade by Godric Gryffindor, it can present itself to a true Gryffindor through the Sorting Hat at a time of need, so Hogwarts won't actually lose the sword.
You'd Expect: That Harry would simply be honest with the goblin, and tell him, without going into details, that they need the sword to defeat Voldemort and that he would hand it over once the Dark Lord had been vanquished. Griphook had already admitted that he was very unhappy with Voldemort's regime, and that he believed Harry did not seek personal material gains or riches. If appealing to the goblin's better nature doesn't work, Harry can simply point out that Griphook is a fugitive from justice, Gringotts is being interfered with by wizards, and his people are on the brink of enduring another age of oppression at Voldemort's hands. ("So if you take the sword from us before we can kill You-Know-Who, you'll still be on the run with nowhere to go, Gringotts will still be under his control, your people will still be suffering at the hands of "Wand-Carriers", Death Eaters will still be in charge of the Goblin Liaison Office of the Department for the Regulation and Control of Magical Creatures, and considering the Ministry's charming new policies that deal with non-humans and muggles...um, what was the rest of your plan again, Griphook?")
Instead: Harry chooses to lie, on one occasion actually grabbing the sword to keep it near him while Griphook is in the room. Needless to say, the goblin becomes suspicious, betrays them during the heist to steal the sword, and is eventually killed by Voldemort, after which the blade returns to the Sorting Hat, making the entire affair pointless. In the film, this gets rectified where the trio doesn't scheme to cheat the goblin, and Harry does hand over the sword as promised, but Griphook still betrays them.
- Voldemort gets his hands on the Elder Wand previously owned by Dumbledore. It doesn't work for him since he's not its true owner. He assumes this is because he did not kill Dumbledore, which would indicate Snape currently owns the wand.
You'd expect: Voldemort to realise that something's not right. His two assumptions about ownership of the wand are mutually exclusive, since Dumbledore took possession of the wand without killing its previous owner, Gellert Grindelwald, which Voldemort knows because he killed Gellert. Therefore, if Dumbledore is the owner then killing the previous owner shouldn't be a necessity, or if the kill is required then Dumbledore shouldn't have owned the wand in the first place, and Voldemort should own it now.
Instead: He follows both assumptions not noticing that they cannot possibly be both right, and assumes Snape owns the wand right now and proceeds to kill who he assumes to be one of his most skilled and useful minions, thinking this would give him ownership of the wand. He also has Nagini do it, which if anything might actually put the snake in charge were his base assumption not flawed.
Additionally: Voldemort concludes that he's not the owner yet, because the wand doesn't perform any differently from an ordinary one, so apparently the difference is palpable, or at least he believes it should be.
You'd expect: That after running into all those complications the first thing he'd do after killing Snape would be to test the wand if it performs properly now.
Instead: Despite there being no rush at all, he just assumes that it has to work now.
- Harry finds out from Snape's memories that Snape always had a crush on his mother from the time they were children. Both coming from Muggle families (half-blood in Snape's case), they enter the wizarding world with glee and remain friends after being sorted into different houses. Lily becomes concerned, however, when Snape starts hanging out with a Dark Magic crowd that espouses hate against Muggleborn witches and wizards, like her. He's also obsessed with what James and his friends do, despite Lily assuring Snape that she finds James as an "arrogant toe-rag" and that it's not healthy for him to fixate on them.
You'd Expect: That Snape would realize the problem in joining a group that wants people like Lily dead. Knowing Lily's sense of justice, she wouldn't go into hiding unless necessary. Also he's in great danger of adopting that same mentality that wants her dead, and that it could ruin their friendship. You'd expect that he would go cold turkey from the makeshift Death Eaters and find a new group and purpose.
Instead: Snape stays with the Slytherin Death Eaters through all his years in school, and doesn't deny that he wants to join with Voldemort. The Last Straw for Lily is when he calls her a Mudblood after she defends him from James and his gang in their fifth year. Lily's so angry that she calls him "Snivellus" and later on when he comes to apologize makes it clear that he's crossed a line.
You'd Then Expect: For Snape to agree to abandon the Death Eaters right then and there in the hopes of saving their friendship.
Instead: He doesn't, and he can't answer Lily's Armor-Piercing Question. Instead he dismisses what he said as a Freudian Slip, which is Not Helping Your Case. Also, thanks to his allegiances, he ends up overhearing the prophecy that leads to Voldemort targeting Lily and her family, cuing a My God, What Have I Done? from Snape.
- Following this, Snape is heartbroken and disappointed that Voldemort did kill Lily instead of sparing her despite Dumbledore trying to protect the Potters, and that only her son with James survived. Dumbledore later tells Snape that Harry has his mother in him.
You'd Expect: That Snape would realize that Harry is not James, despite Harry acting arrogant at times and believing he's above the rules. Harry is a child who, like him, grew up with abusive relatives and seeks refuge in the magical world. You'd also think he would seek some form of self-care to handle his guilt so that it doesn't spiral and hurt others.
Instead: Snape decides to let his Freudian Excuse turn him into a Sadist Teacher. He terrorizes Harry to the best of his ability, promising to get him expelled despite the fact that an untrained Harry would die when facing Voldemort. He also terrorizes Neville, who is an innocent party in this, due to Neville being the other potential Chosen one. Harry and Neville come to loathe Snape and thus don't trust him; this leads to Sirius's death later on, and to no one trusting Snape after he murders Dumbledore. Snape digs himself deeper after cutting off George's ear by accident, which means that he has to wait months for an opportunity to deliver the Sword of Gryffindor to Harry and Hermione, and has no means of relaying Dumbledore's final task until the Battle of Hogwarts. Neville leads a student mutiny when Snape is made headmaster of Hogwarts, and refuses to cooperate.
- Through a Pensieve Flashback and a conversation with Dumbledore's spirit in Fluffy Cloud Heaven, Harry learns what happened between books five and six that nearly crippled Dumbledore's wand hand. To sum up: while poking around the childhood home of Voldemort's mum, Dumbledore comes across a ring that belonged to Voldy's grandpa, which he knows to be a Horcrux. However, it turns out that the ring also has the Resurrection Stone, one of the Deathly Hallows, which can supposedly bring the dead back to life.
You'd Expect: Dumbledore would do what he came to do and destroy the damn Horcrux, while keeping in mind that Voldy will have likely put some kind of protective curse on it. As for the stone, he would remember one of the most fundamental laws of magic: "No spell can reawaken the dead."
Instead: He puts the ring on, hoping to see his dead mother and sister again. Turns out that the ring does have a curse on it, and it almost kills him. While he still succeeds in destroying the Horcrux, Snape is only able to buy him one more year of life. (To his credit, Dumbledore does admit to Harry how stupid he was in putting the ring on, as it proved once and for all that he wasn't worthy of uniting the Hallows.)
What's worse: Since the power to summon the ghosts was contained in the stone alone, there was absolutely no reason to put on the most likely cursed ring even to try and use the stone!
On the other hand: You do have to question Voldemort's logic at choosing the protection measures for the ring. We've seen that artifacts (like the necklace in Half-Blood Prince) can be made lethal to a mere touch. Putting the ring on is quite a specific action that he couldn't reliably expect the thief to do, especially since, to his knowledge, the ring was just a bauble, and of course, it in no way actually prevented the thief from stealing and destroying it.
- After Voldemort finds out that Harry is hunting his Horcruxes, he checks several vaults, finding them all ransacked.
You'd Expect: Voldemort would keep his snake Nagini, who's also a Horcrux, by his side at all times, and preferably under magical protection.
Instead: While he does both these things, he removes the protection on Nagini when he thinks he's won with Harry's death, even though the battle at Hogwarts hadn't even ended. The result is Nagini dies by Neville's hand, and Voldemort loses his immortality and is then killed. It's even worse in the film, where he makes Nagini fight the good guys without even replacing the protective magical cage on her.
- At some point, a rumour starts going around that Scorpius is the son of Lord Voldemort, fathered through the use of a Time Turner. The only things that give this theory any kind of credibility is a rumour that Scorpius's father Draco might have been infertile, and the Malfoys disappearing from public life in the months prior to Scorpius's birth, owing to the poor health of Scorpius's mother.
You'd Expect: Anyone with even a hint of common sense to either take this theory with a pinch of salt, or disregard it for the unfounded nonsense it is.
Instead: It's believed by enough of the wizarding world for Scorpius to be bullied over it in school. And not just the general masses, but even Amos and Harry entertain the theory as well.
- Following on from the above point, Draco understandably wants to put a stop to the rumours about his son's parentage once and for all, so he asks Harry for the Ministry's help in the matter.
You'd Expect: Harry to take advantage of the numerous ways he could go about solving this, even if the wizarding world doesn't have the equivalent of a DNA test. He could follow Malfoy's quite reasonable suggestion and make a public statement about how all the Ministry's Time Turners were destroyed during Order of the Phoenix. Or he could investigate the original source of the rumours and perhaps go about discrediting them - he is Head of the Department of Magical Law Enforcement after all. Or he could suggest that Malfoy take Veritaserum and publicly testify about his ability to father a kid. In any case, he could at least do something.
Instead: Harry's response is to do absolutely nothing, on the basis that "if you answer the gossip, you feed the gossip" - nevermind that a year or two of this is quite clearly shown to have not worked.
- Prior to the start of his fourth year, Albus, resentful of having to live under Harry's shadow, gets into a heated argument with his father. The argument ends with Harry claiming, in the heat of the moment, that he sometimes wishes Albus wasn't his son. He immediately tries to take it back, but Albus just assumes that his father is serious about not wanting him. Later on, Albus (in disguise) brings the matter up with Hermione, who remarks that sometimes, people just say things they don't mean.
You'd Expect: Albus would figure out, upon hearing this, that Harry does care about him, even if they have their occasional differences. After all, regardless of whether he's done a good job of it, Harry's tried his best to support his son over the last few years, and until now, never said anything along the lines of I Have No Son.
Instead: It flies completely over Albus's head, and he continues to delude himself into thinking he's an unwanted child.
- Albus and Scorpius plan to use a more potent version of the Time Turner to travel back to the events of Goblet of Fire and prevent Cedric from being killed by Wormtail and Voldemort. They both know that the murder happened due to Cedric grabbing the Triwizard Cup in the third task of the Triwizard Tournament, and being portkeyed to Voldemort alongside Harry.
You'd Expect: That with this knowledge in mind, the two of them would focus their efforts on stopping Cedric from laying a finger on the cup during the third task.
Instead: Both of their attempts to save Cedric consist of them sabotaging and humiliating him during the first two tasks of the tournament, never mind that at most, this would only slightly impair Cedric's chances of reaching the cup first, due to the tournament's structure. The first attempt does little more than prevent Ron and Hermione from getting together and starting their family, while the second attempt creates an alternative timeline where an embittered Cedric joined the Death Eaters and killed Neville during the Battle of Hogwarts, resulting in Voldemort ruling the Wizarding World.
- While searching for Albus and Scorpius following their escape from the Hogwarts Express, Harry encounters Bane, who warns him that a "dark cloud" surrounds Albus. After finding Albus, Harry seeks advice from a portrait of Dumbledore, who suggests that Harry's love for Albus has blinded him, and that Harry should look for the source of Albus's inner hurt.
You'd Expect: Anything other than what Harry does. Seriously, anything.
Instead: Harry somehow comes to the conclusion that Scorpius is a threat to Albus, on the basis that Scorpius might be Voldemort's son, a theory that - as has been mentioned before - has almost no evidence to support it. He then proceeds to deconstruct the Papa Wolf trope by forcing Albus to avoid Scorpius, and bullying the Hogwarts Headmistress into changing school timetables and keeping an eye on the boys with the Marauder's Map in order to keep them apart. Naturally, all this does is make things worse.
- The Augurey is ultimately revealed to be planning to use the Time Turner to alter history and prevent Voldemort from being killed.
You'd Expect: Them to take advantage of the many ways they could do this, on their own, while leaving everyone else none the wiser. They could go back and either knock off Harry before the Battle of Hogwarts, or forewarn Voldemort that attempting to kill baby Harry will not end well for him (in fairness, they do eventually try the latter).
Instead: They insist on following through with a prophecy that requires Albus to bring about the events of a Bad Future. While the Augurey is able to manipulate him and Scorpius into unknowingly doing this, they don't take into account Scorpius having regrets and using the Time Turner to undo his and Albus's mistakes.
You'd Then Expect: The Augurey to realise their folly, and decide to rewrite history on their own, prophecy be damned.
Instead: Still wanting to fulfill the prophecy, the Augurey kidnaps Albus and tries to force him to play his part in the prophecy, by having him perform a task the Augurey could quite easily do themselves. The Augurey doesn't even do something like put Albus under the Imperius Curse, on the basis that it would mean not following the prophecy to the letter. Unsurprisingly, Albus and Scorpius refuse to cooperate, and end up sabotaging the plan. At which point it finally occurs to the Augurey that they DON'T need to follow through with a prophecy in order to prevent Voldemort's death.
- The climax. The Augurey and Harry face off inside a church. The Augurey manages to trap Harry's allies outside the building with a spell that seals the church doors and seemingly prevents Harry's allies from magically unlocking them from their side.
You'd Expect: They would simply apparate inside the church. Or just blast down the doors or walls with Reducto. They can quite easily repair the damage before any muggles notice it.
Instead: They have Albus magically open the doors from inside the church, putting him at huge risk of being killed by a murderous villain.