The reason Hugh is so passionate about kicking the shit outta Team Plasma? Five years ago, Plasma grunts kidnapped his sister's Purrloin.
The Purrloin left by his late grandfather, no less.
More heartwarming: It was supposed to be that the Purrloin, which evolved into a Liepard, became devotedly loyal to the Triad and Team Plasma and wouldn't leave the Poke Ball when Hugh got it back due to it. It turns out that at some point during the post-game, Hugh's sister was able to remedy it with some tender loving care and now has her mon back. Maybe Earn Your Happy Ending?
Some of the Memory Link scenes can be this, especially with the emotional piece of music that plays. Special mention to the Drayden and Brycen ones where Drayden and Alder both share a So Proud of You moment with their students.
The ending where the player character walks back down Aspertia City's streets and runs toward Mom. Together they go back to their house.
Occasionally random trainers will say something heartwarming. For example, there's this one Roughneck (a trainer class often depicted as thugs) on Route 9 that demands your pokémon if he defeats you. After the battle he wonders why people always think he is serious and, after talking with him again, proudly says that his policy is to take weak Pokémon and raise them with tender care until they're good and strong.note This same trainer was in the original Black and White (same name even, but there he had two Pokemon where here he only has one), where if you talk to him after beating him, he would say that he wouldn't stoop as low as Team Plasma, who steal Pokemon. D'aaawww.
Another instance is on Route 4 in Black 2 where there is a Roughneck and Biker who challenge you by saying usual threatening stuff. Their Pokemon though are two Ridiculously Cute Critters (Cottonee and Petilil), and when they lose, they immediately start worrying that their "babies" are hurt.note They don't appear in White 2, but a pair of Twins do with the same two Grass-types. Also counts as a Crowning Moment of Funny.
You know how there's a huge amound of Brick Jokes in random NPC dialogue? There's one in particular that stands out as a major Heartwarming Moment: back in the first game, you see a Plasma Grunt in N's Castle with a Patrat. He says the Pokemon has become attached to him, but as far as he's concerned, a Pokemon is just a simple tool, and can't understand why a Pokemon would act like that. Come this game, a Grunt with a Patrat can be found in the Old Team Plasma house in Driftviel...
After defeating Elesa, she allows you to walk down the fashion runway with her and her three Beauty trainers.
In the credits after beating the Elite Four the first time, in some files, she blows your character a kiss.
In the post-game, if you visit the house of the protagonist from the original games in Nuvema Town, you'll find out that the protagonist of Black/White has left Unova to try and find a friend who went missing two years ago — N.
Plus, it turns out that their mother and yours are old friends, after they met for the first time when Hilbert/Hilda's mother was a trainer and went to a pokemon center, where your mother used to work. From that point on, Hilbert/Hilda's mother will heal your pokemon when you talk to her just as your own mother does.
N's new theme, which reflects the Character Development N's been through since the events of the first games.
As opposed to his sprite in BW, his BW 2 sprite has a happy smile. Despite all the tough shit he's no doubt been through.
Speaking of N, the first time you encounter him on Victory Road is this when he encourages and supports you. What makes it even more touching is that he will recognize any of his Pokemon that you caught if they are on you. Aww, he still remembers and recognizes them.
Not only that, but whenever you catch one of N's Pokemon, it starts with maximum happiness, the only Pokemon in the series that have this. Even if he only had them for a short time, N was incredibly kind to these Pokemon.
Bianca's newfound cheerfulness. While she already a Genki Girl in the first games, there was also often this atmosphere of selfdoubt around her; she often felt weak in comparison to the player character and Cheren, and she didn't really know what she should or could do in life. It's great to see that her character development from the first games payed off as she has really hit her stride as Prof. Juniper's aide in Black 2 and White 2. She's reliable, happy, curious about studying pokémon and a great battler.
Especially so right before Bianca's Memory Link battle where she starts happily reminiscing about the journey she had two years ago with Cheren and the previous player character. She then has you go along with her to take the first steps into Route 1, like what she did with her friends back then.
Hell, Bianca's new remix of her leitmotif is pretty Heartwarming on its own.
Many NPC-related callbacks to the original games count, though there's one in particular you can find in Castelia City. In the original, there's a small cafe on Narrow Street where you can find one of the suits-and-shades men. He relates that the song being played reminds him of leaving home for the first time, and how his mother cried then. Come back in the sequels, and the same guy is there... who will tell you how his mother cried when he finally returned home.
An old man in a house on Route 23 has been discouraged from trying to beat the Elite Four, and he gives you TM35 for Flamethrower...and despite that, he still has a Haxorus in the house who he can't bear to part with. Becomes a Crowning Moment of Funny when you see the Haxorus sitting there watching TV.
A lot of the good endings to the Pokestar Studios movies are heartwarming. Sometimes, the strange endings are heartwarming in their own, twisted way as well. May overlap with Tear Jerker.
Mystery Doors of the Magical Land has your trainer play the part of a spoiled prince/princess who ends up being trapped in another dimension by an evil witch. The good ending of the final movie has the character see the errors of his/her ways, and the ending narration says that the prince/princess goes on to rule a prosperous kingdom as a good and kind king/queen. The strange endings can be considered heartwarming as well, even though they want to stay and marry a plush toy(female character) or the queen(male character). The witch/queen doesn't object to it, and not do what she was planning on doing to the character.
The good ending of the final The Giant Woman! film. The eponymous character is restored to normal by The Power of Love. It's even more heartwarming considering she spent the majority of the movie talking rather harshly to you, her own boyfriend/sister, because of fear and frustration.
In the final "Timegate Traveler" film, your character admits to Future Being Ledian that they were wrong to come to the future, and returns some minor things there. Then, Ledian commends you for saving the lives of so many humans. The real kicker though is right here:
...And so I was able to safely return to my own era... ...If I hadn't returned my research samples to Ledian before coming back, then I would have brought back the Evolution Stone, which would have caused the Bug-type Pokemon of my era to evolve at a rapid pace, and they would have eventually revolted against us humans... ...I never would have thought that I would have been responsible for changing the fate of the human race... ...It still remains to be seen whether changing the future like I did was indeed a good thing, though... ...However, before I changed the future, Ledian looked down on all other life-forms and lived all alone.. ...I hope that in the future that I brought about, Ledian will at least feel a little less lonely. That's all I can really do right now...
If your rank as a movie star is high enough, one of your fans is a current member of Team Plasma who shyly asks if it's okay for them to be your fan before giving you a gift.
There's a little boy who's just so overjoyed to meet "a person from the movie", who just makes you go "aaawww".
A minor one, but if you play as Rosa and ride the Ferris wheel with Dancer Dirk in spring, he'll reminisce happily about his time with Hilda.
While even he admits that it's hard to do, N calls Ghetsis "father" and tries to convince him to become a better person after you defeat him. This is the man who used and lied to him all his life and turned on him as soon as N stopped being useful and yet he's still perfectly willing to try and help him like he would anybody else.note It doesn't actually work, but the sentiment is still strongly felt.
If you watch celebrity TV shows after trading a Pokemon to Yancy or Curtis, they may mention the Pokemon you traded to them, saying that it was traded to them by a dear friend. Aww...
The ferris wheel rides with Yancy/Curtis is just full of adorable. Also after making the required calls to enable trading with them, subsequent calls will have their portrait in a permanent blush.
Minor one: seeing the long line before the Casteliacone stand after becoming Champion of Unova and spending much of the game as one of the only customers. It's pretty sweet to see the woman behind the counter almost literally jumping for joy, especially because she always kept working hard and never gave up hope of the Casteliacones becoming popular again. Even better: it's all thanks to you, as its newfound popularity is the result of a rumor that the new Champion apparently likes Casteliacones.
It wasn't the only spot. There is a man in Humilau who was able to sell more homes for rent thanks to your influence as well.
Further helping matters is that this game actually starts to downplay/avert Dude, Where's My Respect?. In addition to the two above, the ending actually shows the player character actually celebrating his/her victory with the Elite Four and the Gym Leaders.
At least when playing as a male, if you've completed the Yancy side quest, while watching the "Celebrity" channel on a TV it'll say Yancy (as stage persona Nancy) is about to perform a song she wrote titled "Xtransceiver Love" clearly about her and Nate.