Brick Joke: Mrs. Weasley warns Fred and George not to blow up a toilet. They jokingly tell Ginny they'll send her a Hogwarts toilet seat. Fast-forward to the end, when Dumbledore says that the twins attempted to give Harry a toilet seat while Harry was out for three days, assuming it would make him laugh.
Cold Flames: Hermione puts some non-burning magical fire in a jar to keep the trio warm in winter. Later she uses it to trick Snape into thinking his robes have caught fire and scoops it back into the jar when she's done. (In the film, the latter is changed to the regular kind of fire.)
Counterspell: Most directly seen when one teacher tries to curse Harry off his broom while another tries to counter it. The counter-curse was not entirely effective, even though the latter teacher was more skilled than the former, suggesting that counter-spells are imperfect as a defense. More common practice is to use Shield Charms, which block or deflect weak spells, or just use similar spell of equal power so that the two cancel out.
Cultural Translation: Changing the title from Philosopher's Stone to Sorcerer's Stone is not strictly an example of this, as the words "philosopher" and "sorcerer" don't mean anything different in the U.S. than they do in the UK. The thinking was that the word "philosopher" would evoke "serious impenetrable text" rather than the intended "magical adventure".
Vernon: Get the mail, Dudley. Dudley: Make Harry get it. Vernon: Get the mail, Harry. Harry: Make Dudley get it. Vernon: Poke him with your Smeltings stick, Dudley.
Deus ex Machina: A rare instance where this is pulled off convincingly and smoothly. Since Harry's mother died to protect him from Voldemort, her love had a lasting effect on him that gave him protection against physical contact with Voldemort, as Dumbledore explains. It's forgivable because The Power of Love was meant to be symbolic and double as a moral message.
Did Not Die That Way: Harry lived in the knowledge that his parents have died in a car crash for 10 years, when it is revealed to him by Hagrid that they had in fact been murdered by Voldemort.
Among other things, this is the only book that deviates from Harry's third-person-limited POV after we're in his head for the first time. During the troll scene, we're briefly in Ron's head as he decides to do Wingardium Leviosa, and when Harry's broomstick is acting up during the Quidditch match, we stay on the ground with Ron, Hermione and Hagrid. Other books do switch POV, but only in full chapters designated for it.
The attempt to kill Harry by knocking him off his broom mid-Quidditch match is hard to take seriously after reading the following books, in which Harry gets successfully knocked out mid-flight several times and securing his landing is always rather trivial. For those keeping count, that means Cormac McLaggen came closer to killing Harry (five books on) than Quirrell did.
Some of McGonagall's early behavior, such as reading a map in cat form openly long enough for Vernon to see her doing so is very uncharacteristic for her in later books.
Fantastic Racism: Harry's conversation with Draco in Madam Malkin's Robes lays the groundwork for the concept of Blood Purity, which will fully take off in the next book and become one of the central conflicts of the series.
Fire-Forged Friends: Harry and Ron become friends with Hermione after they fight a mountain troll together.
One of the first things Harry learns about the wizarding world is that it's dangerous to mess with goblins and flat-out mad to try and rob Gringotts, but Voldemort manages to attempt this a few chapters later, offscreen. Then Book 7 rolls around …
The high-security vaults are guarded by dragons.
Vernon and Petunia glare at Harry when he says "Platform 9 and three quarters" but only Vernon calls idea of the weird platform "rubbish". We learn in Book 7 that Petunia has actually stood on the platform. She was probably quiet because she was reminded of it for the first time in years.
Even subtler, when Hagrid shows up at the island where the Dursleys are holed up, Vernon calls Dumbledore an "old fool". How would he have any idea whether Hogwarts' headmaster is old or not? When he and his wife discussed Harry's letter, Petunia must have told him that Dumbledore worked there when Lily was at school.
Harry claiming that Voldemort will turn Hogwarts into a school for the Dark Arts.
While Snape is a Legilimens to an extent, he is much better at Occlumency, which is the defense against Legilimens.
In terms of foreshadowing strictly inside the plot of Book 1 itself, when Hagrid explains the professors who arranged for the traps to protect the Mirror of Erised, and likewise the Philosopher's Stone, Quirrell is among those listed. Later, when they are proceeding through the traps to get to the Philosopher's Stone to prevent who they think is Snape from getting it, they enter Quirrell's trap room and discover a knocked out Troll, which gives away an early clue that Quirrell was the one who released a troll into the castle on Halloween, and that it is in fact Quirrell, not Snape, who was searching for the Stone.
Harry tried asking Dumbledore what the latter sees in the Mirror of Erised. When returning to bed, Harry realized that Dumbledore wasn't being truthful with his answer, and then telling himself that it was something personal for Dumbledore.
Voldemort correctly surmising that Harry lied to Quirell about having the Stone during the climax at the Mirror of Erised. It seems like he's just being Genre Savvy or that Harry didn't lie too well. Voldemort's actually employing Legilimency, though it won't be identified as such until Book 5.
Right there on the Chocolate Frog Card: Dumbledore is particularly famous for his defeat of the Dark Wizard Grindelwald in 1945, which is when he scored the Elder Wand.
Forgot I Could Fly: Ron, to Hermione, after she can't light a fire to burn the Devil's Snare: "HAVE YOU GONE MAD? ARE YOU A WITCH OR NOT?"
Generation Xerox: The departure for Hogwarts. In this book, Ginny is shown crying about how she has to wait to go to Hogwarts and wants to go now as she sees her brothers off at the train station. In Deathly Hallows, she and Harry's daughter, Lily, are shown doing the exact same thing when she sees her brothers off to Hogwarts.
Also some other names from the Chocolate Frog cards.
Idiot Ball: McGonagall's summarily dismissing Harry's concerns about the Stone. Even if his concerns were far-fetched, the fact that eleven-year-olds knew about a top secret item should have alerted her to the presence of a major security leak, and the possibility that someone else could have learned about the item. At the very least, she should have demanded to find out everything they knew, and where they learned it.
Innocuously Important Episode: On first reading, about half the chapters appear to be self-contained bits of either character development (the troll attack, the Mirror of Erised) or just some fluffy fun (Hagrid and Norbert). All of them suddenly become important during the climax, and a few even show up again later in the series.
Ironic Echo: When Hermione mentions that she has no fire to use on the Devil's Snare, Ron shouts at her, "Are you mad? Are you a witch or not?" Hermione repeats this line to him, with the word "wizard" in place of "witch" in Book 7.
I Thought It Meant: In-Universe; after the Remembrall retrieval incident, Harry hears Professor McGonagall ask Professor Flitwick if she can "borrow Wood for a moment". Harry thinks he's about to get caned, only to discover that Oliver Wood is the Gryffindor Quidditch Captain.
A Minor Kidroduction: The book starts with Harry being left to the Dursleys as a Doorstop Baby. The second chapter skips forward nearly ten years to the preteen Harry we'll follow for the rest of the novel.
Mirror Scare: Played with. The first time Harry looks in the Mirror of Erised and sees dozens of people behind him, he covers his mouth to stop himself screaming and spins round to find … nothing.
While the series wouldn't bring them out in full force until later, they would end up using bits from this book, besides the use of magic, to denounce it. Some more ridiculous than others.
The line "There is no good or evil, there is only power, and those too weak to seek it" is called "standard Witchcraft, and standard Illuminist doctrine"; we're told that "since a child's inherent nature is evil, he will find such philosophy more appealing than the Gospel of Jesus Christ". Ignored is the fact that the character putting this "philosophy" forward is the villain. And starting from the point that a child's nature is inherently evil.
When students are paired off to practice levitation, "Harry's partner was Seamus Finnigan (which was a relief, because Neville had been trying to catch his eye)" — to Cutting Edge, an eleven-year-old boy's not wanting to be paired off for a laboratory-style class with the school klutz is a suggestion of homosexuality.
"Harry was eleven (11) when he was admitted to Hogwarts School of Witchcraft and Wizardry. The number eleven is considered sacred to the occultist, as it is the first primary number." Er, no, the first prime number is TWO. Followed by y'know, three, five and seven. Which makes eleven the FIFTH prime number and HOLY SHIT! FIVE IS THE FIRST PRIME NUMBER! SATAN! Not to mention the fact that all English children start Secondary School at that age.
Neville: You can't go out, you'll be caught again. Gryffindor will be in even more trouble … I won't let you do it. I'll — I'll fight you! Ron: Neville, get away from that hole and don't be an idiot— Neville: Don't you call me an idiot! I don't think you should be breaking any more rules! And you were the ones who told me to stand up to people! Ron:Yes, but not to us''.
Motor Mouth: This is what Hermione has in her first appearance.
Mr. Exposition: Hagrid is essentially this because of how often he accidentally lets slip the crucial information that the protagonists and the audience need to know.
Muggle Security-Guards Are Useless: Not only is the guard at the train station justifiably ignorant of Platform 9¾, but he dismisses an eleven-year-old who's bewildered and alone as a "time waster". Isn't reuniting lost children with their escorts a part of his job?
My Parents Are Dead: This is the point at which Harry's first conversation with Draco goes from bad to worse. Harry also dismisses the possibilty that the Mirror of Erised is clairvoyant on this basis.
Naïve Newcomer: Harry, understandably much more so here than in later installments.
No, Except Yes: After Dumbledore's ides of "a few words before the feast can begin" (nitwit, blubber, oddment, and tweak), Harry asks Percy if Dumbledore is crazy.
"Mad? He's the greatest wizard in generations! But yes, he is a little mad."
Noodle Incident: Dumbledore's defeat of the Dark Wizard Grindelwald, as mentioned on the Headmastser's Chocolate Frog card, appears to be this at first. It ultimately gets subverted as we find out exactly what happened in the last book.
How Dumbledore exactly got his "scar in the shape of the London Underground system" is never actually pointed out or brought up again.
Not So Different: As we learn later in Book 7, Dumbledore, like Harry, also sees his family alive and happy again in the Mirror of Erised.
One-Person Birthday Party: After Harry's 11th birthday is forgotten by the Dursleys because of the flood of letters from Hogwarts, Harry sings the "Happy Birthday" song to himself.
Only Smart People May Pass: Some of the obstacles the staff placed in front of the stone. They weren't all considerate enough to warn you in advance, however — if you don't already know how to deal with Devil's Snare, you have about ten seconds to figure it out before it crushes you. Snape's potions-in-bottles puzzle is the closest fit (although why he felt the riddle had to rhyme is anyone's guess). The only real aversion to this was Quirrell's obstacle, fighting a troll, which, luckily, the Trio didn't have to deal with (again).
Open Secret: Dumbledore assures Harry that his confrontation with the Big Bad is a complete secret, which naturally means the whole school knows.
Out-of-Context Eavesdropping: Harry overhears what seems to be Snape forcing Quirrell to help him steal the Stone. It turns out Quirrell was after the Stone and Snape, suspecting as much, was trying to scare him into giving up on it.
Plot Tailored to the Party: The obstacles protecting the Stone employ the use of each of the trio's strengths: Harry's flying skills, Ron's chess-playing skills, and Hermione's logic. Plus the troll that all three of them stopped earlier in the story, but which turned out to be Already Done for Them.
Harry meets Draco Malfoy while shopping for robes before meeting him on the Hogwarts Express.
He also meets Quirrell in the Leaky Caudron.
Pun: Diagon Alley (for "diagonally", reflecting its kinked medieval shape).
Red Herring: Snape not only in this story, but he also turns out to be the ultimate one in the series.
Right Behind Me: Happens to Ron when he's complaining about Hermione after the Charms lesson.
Sadist Teacher: Snape, who is a complete Jerkass to most students (especially Harry) and is absurdly biased towards Slytherin House. However, he's a mere precursor to some genuinely evil Sadist Teachers introduced in Books 5 and 7.
Screw the Rules, I'm Doing What's Right!: Harry Potter gives a whole speech to this effect prior to the climax of the first book: "If Snape gets hold of the Stone, Voldemort's coming back! Haven't you heard what it was like when he was trying to take over? There won't be any Hogwarts to get expelled from! He'll flatten it, or turn it into a school for the Dark Arts! Losing points doesn't matter anymore, can't you see? D'you think he'll leave you and your families alone if Gryffindor wins the house cup?"
Erised stra ehru oyt ube cafru oyt on wohsi(I show not your face but your heart's desire.)
Second Episode Morning: The morning after he learns the truth, Harry decides it must have been a dream before he opens his eyes. Then he finds himself still in the hut, with an owl tapping on the glass.
Serial Escalation: The Hogwarts letters that Vernon suppresses from Harry before he gives up and (unsuccessfully) takes the family on the run: On Wednesday, Hogwarts sends one letter to Harry in Privet Drive. On Thursday, they send three; on Friday, twelve, on Saturday, twenty-four; on Sunday, even though there is "no post on Sundays," they come spewing down the chimney; and finally, on Monday morning, the owner of the hotel where the Dursleys (and Harry) stay to hide from the letters mentions that there are roughly a hundred of them at the front desk. Ultimatel
Taking the Heat: Hermione for Ron and Harry in the incident with the troll.
Talk About the Weather: Quirrell starts muttering about the weather whenever someone asks him about his turban.
To Be Lawful or Good: Hermione starts off as a well-meaning but often painfully lawful student, always mindful of the rules (no matter how ridiculous) and scornful of Harry and Ron for breaking them. Circumstances push her a bit in the direction of good as it becomes clear that quietly following the rules is not enough. The time Harry and Ron broke school rules in order to save her life from a troll probably helped lead her to that conclusion.