From the Book:
- When Harry says that of course he wants to move in with Sirius, and Sirius beams.
...for a moment, he was recognizable as the man who had laughed at Harry's parents' wedding.
- Harry being so quick to say of course he wants to move in, when you remember he only really got to know Sirius a few hours ago.
- Sirius being so hesitant to even ask Harry to live with him, understanding that Harry's already set up at the Dursleys' and might be attached to that home and family. Of course, Sirius has no clue how awful the Dursleys are, so he doesn't know that getting away from them is the only thing Harry wants, but you can feel how hopeful Sirius is that he can finally start fulfilling his obligation as Harry's godfather.
- Sirius' parting words before flying away on Buckbeak:
- For a while, Harry had believed that it was his father who had cast the Patronus, when he had actually seen himself. When he tells Dumbledore how stupid he felt, Dumbledore tells him no and that his father was there indeed, albeit in spirit.
Dumbledore: Your father is alive in you, Harry, and shows himself most plainly when you have need of him. How else could you produce that particular Patronus? Prongs rode again last night.... You know, Harry, in a way, you did see your father last night.... You found him inside yourself.
- Despite being all of thirteen/fourteen-years-old, with one of them badly injured, Ron and Hermione fling themselves onto Sirius unarmed to protect Harry from him, and Ron tells him that if he wants to kill Harry, he'll have to kill him and Hermione too. Made even more poignant in that Harry observes something flicker in Sirius's eyes at Ron's words, no doubt because they reminded Sirius of how he was willing to sacrifice himself for James.
- Also, Fred and George making Harry feel better with some expertly-placed humor when Malfoy is taunting him about fainting around the Dementors.
- The fact that Snape was entrusted with brewing Lupin's werewolf potion and making sure it was always available. He still despises Lupin for his actions in their school days, but he does his duty.
- Keep in mind, judging from how Lupin says he was picked to be prefect to hold back James and Sirius and how in Snape's memory Lupin is the only one of the four not partaking or cheering in Snape's bullying, Lupin might be the only one who Snape resents the least as Peter Pettigrew was buried years ago, Sirius was the one who came up with the idea to lure him to the Shrieking Shack, and James was his main tormentor. Yes, he voices concerns repeatedly about Lupin being hired at all (and also does his best to hint at Lupin's true identity then blurts it out after all is said and done despite not tampering with the potion all year), but that is mostly because he thinks that with Sirius Black on the loose, Lupin, a known old friend of his, is liable to help him even against the school, and he was out cold for most of Sirius and Lupin's explanation and most importantly for Pettigrew's, which washed Sirius' name clean.
- Sirius mailing Harry a Firebolt and signing his permission slip to go to Hogsmeade (as Harry points out, "That's good enough for Dumbledore!"), which is accepted as even though Sirius is a wanted criminal, he's still Harry's legal guardian.
- Harry's thirteenth birthday was also the first time he ever got birthday cards and presents from his friends. The narration points out that this is the first time in his life he felt glad it was his birthday, especially since his twelfth birthday in the previous year was his worst (although his eleventh in the first was his best, so it's both a bit of a Continuity Nod and Negative Continuity at once).
- Harry's two weeks of freedom in Diagon Alley is also pretty heartwarming and awesome. After a particularly horrible stay with his awful family and a near-miss with a Despair Event Horizon, he is given a very generous amount of slack from Minister Fudge and is given free reign within Diagon Alley, including getting to study outside the ice cream parlor!
- It becomes Harsher in Hindsight after watching the film, in which it is one of the first things from the films to be mercilessly left out.
- Cedric Diggory's Establishing Character Moment: he's an excellent Seeker, but is also extremely honorable. Athough he catches the Snitch fair and square, the minute he sees that Harry has fallen from his broom, he immediately demands a rematch, realizing that the Gryffindor seeker was sabotaged. Cedric either wants to win fairly or not at all, and he hates that this victory came by default.
- The fact that Wood supposedly told Cedric the loss was fair.
- The last two victorious Quidditch matches against Ravenclaw and Slytherin, the Grand Finale of the original Quidditch storyline. What's particularly heartwarming about it is the fact that they were doing pretty badly at first—-Harry lost not only his first game but ended up getting his broom destroyed. Wood was half convinced that he would leave Hogwarts with no Quidditch Cup. And yet...they did it!
- The whole backstory of how the Marauders became Animagi. They learn that their friend is a werewolf and, instead of abandoning and shunning him like the rest of the wizarding community would, they spend three years learning a particularly difficult piece of magic for the sole purpose of helping Remus during the full moon. This also causes a bit of a tearjerker, when you realize just how loyal Peter was to his friends when he was younger and think what must have happened to make him become a traitor.
- Also the fact that James, Peter, and Sirius were twelve and didn't abandon Lupin when most older wizards would.
- A subtle one: Sirius has survived for 12 years in Azkaban (an unheard of length for a prisoner to last) solely due to the knowledge that he didn't kill James and Lily. He escapes when he learns that Harry is in trouble, and lives a hellish life out in the woods for almost a year while he desperately seeks a way to protect his godson. And upon seeing each other for the first time in twelve years, Harry immediately accuses Sirius of murdering James and Lily, even going so far as to attack him head-on. The fact that Sirius never raises a hand to protect himself, because as he puts it "I as good as killed them", and never even gets upset at Harry for the misunderstanding...
- Lupin sticking up for Neville when Snape insults him before the boggart lesson. Pretty much all of the teachers think of Neville as useless and tend to get exasperated with him, but Lupin notices his lack of confidence and tries to help him get over his fear of Snape.
- Then you hear McGonagall describe Pettigrew: a plain kid with not much brains or talent that she feels she was perhaps too stern with. No doubt Neville reminded Lupin of him...
- Sirius breaks into Hogwarts on Halloween. Why then? Because it's a full moon and he doesn't have to do the one thing he fears the most - he doesn't have to face Remus, as Lupin is currently werewolfed in his office.
- The speed and ease with which Lupin accepts Sirius's innocence suggests that, even after all this time and despite the seemingly overwhelming evidence, he still harboured some doubts about his friend's guilt.
- Elaborating on this, Lupin lost his three best friends over the course of two days and spent the better part of thirteen years alone and friendless. Meanwhile, Sirius was locked in prison for that same period of time for a crime he didn't commit and had everyone in the wizarding world thinking he was everything he had fought against. Once Lupin enters the Shrieking Shack and Sirius confirms what happened, they embrace, each overjoyed that they have one of their best friends back.
- The fact that the whole student body is sad to see Lupin go. To them, he was never a monster but one of the best teachers they'd ever have.
- Hell, when Harry finds out from Hagrid that Lupin resigned, he immediately runs to Lupin's office to beg him not to leave.
- Crossing over with CMOA and Tear Jerker:
Peter: The Dark Lord... you have no idea the weapons he possesses... he would have killed me, Sirius!
Sirius: THEN YOU SHOULD HAVE DIED! Died rather than betray your friends, as we would have done for you!
- Hagrid sticking up for Hermione to Harry and Ron, telling them gently but firmly that they should be better than this and not let their friendship with her go. Hagrid is Harry's friend and loyal to him through and through, but he's not above telling him when he's gone astray.
- The scene when Lupin has tea with Harry while the others are in Hogsmeade. He makes reference to the tea leaves incident (where Trelawney saw a symbol of death in his mug) and checks in about whether it's bothering Harry and puts him at ease. It seems like he's acting like the uncle or family friend he wasn't able to be.
- Sirius risks his safety just to see Harry fly on a broom - just once, he gets to watch his godson fly.
- Dumbledore telling Hermione to take Harry back in time, no doubt breaking a dozen rules and risking a threat to the timeline itself, in order to save the prisoner from a serious fate. Made more heartwarming by the Fridge Brilliance: he couldn't do anything to save Sirius twelve years ago, but he darn well will this time.
- Even as Harry and Hermione are rescuing him with time being of the absolute essence, Sirius still asks what happened to Ron and makes sure he will survive their earlier encounter before leaving.
- Sirius also kindly gives Ron a pet owl to replace his rat.
- Ron holding out the tiny owl to Crookshanks to confirm that it's "definitely an owl" after disliking the cat for most of the past year.
- Crookshank's friendship with Padfoot. Especially when he lies on Sirius's chest to shield.
From the Film:
"You have-" "My mother's eyes."
- The scene where Lupin tells Harry about his parents, combined with the soft music in the background, did it for me. The music in question
- Lupin and Sirius hugging upon reuniting with each other in the shrieking shack.
- Keep in mind that Sirius absolutely loved flying (as evidenced by him enchanting his motorbike to do so), then remember his extremely delighted reaction to riding Buckbeak. This was his first time flying after twelve years of being wrongfully locked up, and he's doing it with his beloved godson, who loves the activity just as much as he and James did. Of course he's having the time of his life!
- Also, Harry and Sirius's goodbye at the end.
Sirius: It's cruel that I got to spend so much time with James and Lily and you so little. But know this, the ones that love us never really leave us. And you can always find them in here. (places his hand over Harry's heart)
Harry: "But, you're innocent!"
Sirius "And you know it! For now, that'll do."
- The music really upped the heartwarming tear-jerker aspect of those scenes. Even better when you realize that the theme is titled "A Window to the Past," which is so fitting for this book/movie and its context to the rest of the films.
- The scene with Sirius and Harry being parted in the film is even more poignant; Sirius doesn't care in the slightest that the wizarding world does not know he is innocent - as long as his godson, the one living reminder of his friends Lily and James, does. That's all he wants.
- Just before they say goodbye, Sirius mentions how much Harry looks like his dad. Normally in the books, Harry comes off as either indifferent or slightly irritated at constantly being told this, but here, he grins and finishes the sentence. You can tell he's happy just to have a connection with Sirius.
- Before Sirius flies off, he also takes the time to compliment Hermione by saying "You really are the brightest witch of your age." Cue Hermione giving him a soft smile in return.
- In order for the Patronus spell to work, one must think of a strong, happy memory. After a failed attempt, Harry mentioned that there is one memory that might be strong enough. He tries it and it manages to stop the Boggart Dementor. He later tells Lupin that the memory was of his parents. Harry didn't even know if it was real or not, but it worked.
- In Prisoner of Azkaban, there's a very quick moment, but one that also doubles as a CMOA, when Harry, Hermione, and Ron are being threatened by werewolf-Lupin, and Snape's first, knee-jerk reaction is to get between the kids and the werewolf and throw out his arms in a "oh-no-you-don't" gesture. It's even better because this wasn't an "oh, meh, I gotta go save Potter's sorry life again" moment; it was a knee-jerk reaction on Snape's part.
- He even does it twice: When he and the trio all fall to the ground after Lupin tries to attack them, he immediately jumps to his feet and throws out his arms again. The implication in that scene is that, while Snape may have his Jerkass moments and personally can't stand Harry and his friends, he's still a teacher, damn it, and he won't let anyone hurt his students.
- What's even more awesome: just before he saw the werewolf, he was boiling with rage over Harry assaulting him. The second he sees the werewolf about to attack the kids, he goes from "what the fuck, Potter," to "get behind me, children."
- Also he tells Dumbledore earlier on that he wants Harry to know the truth about Sirius Black. Harry is nearby, pretending to sleep in the Great Hall, and is confused.
- While the short scene with Harry and his roommates eating those strange candies is supposed to be there for comic value, it's also heartwarming in the sense that it's one of the few times in the entire series where we see Harry look like the young boy that he still is - enjoying some pure fun with friends with all of his usual worries at the back of his mind.
- Sirius on Hogwarts:
Sirius: It's beautiful, isn't it? I'll never forget the first time I walked through those doors. It'll be nice to do it again as a free man.
- Doubles as this and a Tearjerker, but watch Petunia when Aunt Marge is insulting Harry's parents. She politely laughs along when Marge is insulting James, but when she starts on Lily, Petunia stops smiling. However much she may have resented her, Petunia misses her sister, which she outright says to Harry years later in The Deathly Hallows, Pt. 1.