Snape's gift to Lily isn't just an act of love. The rose contains happy memories...many-if not all- of which involve him in some way. In other words, whenever Lily sniffs it, she's not only getting an instant picker upper: She's also getting an immediate reminder of how happy Severus specifically makes her. YMMV on how intentional that was on his part, but it certainly doesn't hurt his chances with her any.
Kitty has a Somail Cat, which are often said to resemble foxes. Evangeline is described as having fox-like features.
Meanwhile, Evangeline's own cat is described as having ginger fur and blue eyes, while Kitty has red hair and blue eyes.
Everyone who has ever betrayed Bertha smoked. That's not the Fridge Brilliance. The Fridge Brilliance is that Bertha striking the cigarettes, then flushing them symbolizes her considering but ultimately choosing not to betray herself.
At first glance, Matilda Macdonald seems like little more than an uneducated woman who was foolish and irresponsible during her youth. Then you learn her backstory, and realize that by using contraceptive charms-albeit poorly cast ones- she actually did exhibit some level of responsibility, as opposed to merely conceiving a child through sheer carelessness. Likewise, she actually did strive to be a good student in her O.W.L year, and only left school as a result of being unable to endure the relentless bullying she faced any longer. Finally, she wasn't just some silly girl who naively fell for a handsome boy's charms: She was manipulated by the future Dark Lord himself! Thus, she really wasn't half as foolish or irresponsible as one might think.
Lily's comment in "Betrayal" about the school newspaper being formed seems like an offhand remark of no real significance. Come Chapter Eleven however and it matters, big time.
James and Sirius encouraging Regulus to injure himself at the next match is intended as "harmless" teasing. However, he actually does fall off his broom at the next match and needs the Hospital Wing.
Regulus catching the Snitch isn't just him winning the game. It's also symbolic of him realizing that love, acceptance, and moral purity-essentially, everything the Snitch symbolizes throughout the chapter- aren't beyond his reach.
Leslie's detailed description of the waitress' sexy uniform in chapter 6 may not just be her having a flair for detail. After all, she is strongly implied to be a lesbian.
Mulciber's comment that Avery "always goes for tiny tits." He doesn't say girls WITH small breasts, but small breasts themselves. It's a subtle example of how he views women as objects rather than people, and how he projects his own views onto others. Also in the same scene, he automatically assumes Snape is only offended by him referring to Lily as a Mudblood, as opposed to objecting to the slur as well as the objectifying statement.
Chapter Ten ends with Mary receiving a letter from her mother, promising to share a secret with her. Mary's recollection in Chapter Fourteen is that secret.
The emphasis on Snape's feet facing away from the group in Chapter 12. Feet pointing away from someone is a form of body language expressing discomfort.
Marlene (most likely) knows that Remus is a werewolf, as indicated by her grin when Remus claims he was asking about why she wrote her article for no particular reason. The Fridge Brilliance-or rather, Fridge Heartwarming- kicks in when you realize that her suspecting Remus of being a werewolf probably served as a motivation for her writing the article.
Snape's internal monologue in Chapter 11. He accuses James of undressing Lily with his eyes, only to lament that he's never able to see her in any state of undress a minute later. He's proud when Slughorn compliments him on his potion and even visibly smirks, but mentally chastises James for puffing out his chest in pride shortly afterwards. Snape's not just being a hypocrite: He and James really are more alike than either of them want to admit.
Mary's (slightly) misandrist attitude towards men can be explained by the fact that most of her mother's clients are unsavory at best, and likely the only man she really considers to be good-her father- is dead.
Doubles as Fridge Horror, but Mary's automatic Groin Attack in Chapter One makes even more sense given the context when you learn that her mother's "clients" frequent her house, and what type of neighborhood she comes from. In other words, this probably isn't her first time defending herself without a wand.
Chapter Tweleve's last line "then everything went Black" is a pun, as not only are Regulus' final thoughts of his family, but he also literally blacks out.
Matilda MacDonald is usually referred to by her nickname, Tilly. What's her profession? A prostitute. And what was one of her nicknames in school? Tarty Tilly.
Tom Riddle being the boy who got Matilda pregnant may seem out of nowhere initially, until you remember that not only does the timeline work out well (he would have canonly been around her age in school), but who else could have manipulated everyone into thinking she was lying about the child's parentage so easily? Not to mention, her descriptions of him match his canon ones.
Leslie almost certainly has clinical depression. Her best friend and crush died less than two months ago, and she exhibits several of the symptoms: Persistent feelings of sadness for over two weeks, lack of motivation, feelings of emptiness, irritability, and Slughorn notes that her grades have dropped. Despite this, she's received very little emotional support. Adding her (adopted) brother and his father into the equation, it's a wonder she's even able to function each day.
On that note, Regulus most likely has depression too-Inability to concentrate, persistent feelings of sadness, loss of interest in former hobbies, repeated thoughts/excessive dwelling-, and like Leslie is not getting treated for it. In fact, he didn't even tell anyone about his relationship with Veronica until more than a month after she died, so he's had to cope with her loss all on his own. Poor guy.
Mulciber's charming exterior shielding his true cruel nature, his lack of empathy, his torturing that rat when he was younger, manipulation of Maria Zabini, deceitfulness, and impulsiveness suggest he either has or is on his way to developing Anti-Social Personality Disorder.
In-Universe, Remus wonders what would have happened if Mary hadn't been able to fend off Mulciber in time...
