Playing the game on your birthday. The villager who is closest to you may come visit and give you a birthday gift.
Taken to extremes in New Leaf. They go as far as to plan a surprise party for you.
Also in New Leafon the Saturday before your birthday, K.K. Slider will play you the special Ear Worm song 'K.K. Birthday' and mail it to you as a gift from him.
Sable, once befriended by the player, will sometimes share stories from her past with them. One story is about a pair of scissors she received as a birthday present from an old friend who, despite having very little money at the time, still sent her a gift. That old friend? Tom Nook.
In general, the entire process of getting Sable to warm up to you is...well, heartwarming.
A mix of Tear Jerker and this is that she will admit her parents died. She opens up about her most sad things she's experienced, and tells it to you because she trusts you.
Several heartwarming moments in New Leaf have to do with how many of the characters' lives have bettered.
The Able sisters have reconciled, and now run their shop together as a trio.
Timmy and Tommy have grown up a bit, and now run their own store.
Kicks no longer shines shoes on an abandoned stoop and now has his own shop.
Kapp'n, after lamenting so long that he has no sweetheart, is now happily married with a family.
(singing about his wife) I wrote a name in the sand near the sea. She's me best girl. Her name is Leilani.
Lyle appears again and works in Nook's shop, and he appears to be much more cheerful in comparison to his appearance in City Folk.
Franklin no longer has to hide during the Harvest Festival and now works as a chef.
The only character whose life has gotten worse is Mr. Resetti, who's out of a job due to the Reset Center being shut down. You can use your mayoral powers to open it back up, and Resetti will stop by your house, not to yell at you, but to extend his heartfelt thanks.
If you visit the Reset Center enough times, Resetti will begin to open up and eventually give you his picture.
Resetti: I don't really get why, but it seems like you've taken a shine to me.
Despite how much he hates his job at the HRA, Lyle will be genuinely happy for you if your house is displayed in the HRA showcase room.
The "Big Sister" villagers may be more rough-and-tumble than the other female villagers, but when they're close to the player, they absolutely adore the player. Stung by a bee? They'll demand to know "who did this to you" and stick up for you before realizing what happened, sometimes even give you free medicine. Give them a free item that they were willing to pay for? They'll break out in tears and thank you profusely. Absolutely out of nowhere? They may even send you flowers in the mail.
In the film, Sally moves away to follow her dream of becoming a fashion designer/artist. Ai is initially upset, as the two were very close, but a letter from Sally causes her to be more upbeat and follow her dream. Sally returns during the winter to surprise Ai, and helps her save the day.
When Ai is upset earlier in the film, Brewster gives her an IOU on her coffee when she's out of Bells, and Whitney (despite coming off initially as a bit cold), gives Ai some touching advice about friends always being connected, no matter where they are.
Also in the film, Apollo forgiving Ai for accidentally running over his blue roses. They're seen planting more together during the credits.
When you have Brewster's cafe available in New Leaf, Tom Nook will occasionally be there. When you talk to him, he'll mention wanting to order extra coffees for either Timmy and Tommy or the Able sisters on his way out, simply as a surprise to show he appreciates their hard work. Awww.
Also the theory that Jock and Lazy villagers have about Timmy and Tommy: Nook took them in off the streets to work in a nice place.
Yet more heartwarming moments in the Cafe in New Leaf is if you talk to Phyllis there she'll sometimes order two coffees from Brewster, one being for her while the other one is for her sister Pelly.
In Wild World, the working NPCs occasionally have little 'episodes' where they talk more about themselves and their backstories and revealing Hidden Depths. A few of these are quite touching, such as Blathers and Brewster's friendship, Tom Nook and Sable's childhood, and seeing how protective Phyllis can be towards Pelly. Furthermore, despite the distance between Tom Nook and Sable in comparison to their younger selves, they do still care about each other, such as Tom Nook still valuing Sable's words of encouragement and wearing the clothes she sewed for him.
If you spend enough bells, and talk to Sable enough, at the Able Sisters' shop in New Leaf, Sable, Mabel, and Labelle will each give you one of their extra mannequins for your home. They mention that those are valuable, showing how much they trust you.
Sable and Labelle will also both become much more cheerful towards you after you buy enough from them.
It's possible to receive a fourth mannequin from none other than Gracie when you buy a gift from her new store in T&T Emporium.
Sometimes, when one villager asks you to deliver something to another villager, the delivered item (in the form of a present) ends up being a gift to you instead.
Also in the same vein as delivering items, if the villager you're delivering the item to happens to be one that you have a high friendship level with, you might get their picture as a reward from them.
In New Leaf, if you try talking to Cyrus at Re-Tail while he's sleeping, Reese quickly tells you to leave him alone because he's been working so hard, and he needs to sleep.
In New Leaf, if you help Gulliver get to Spain, he will send you a letter calling you his best friend.
Also in New Leaf, reuniting with your moved out villagers on Main Street, even if only for a little while.
It's a short moment, but it always feels rewarding to catch fleas off your neighbors and hear their heartfelt thanks afterwards.
If you give a sick villager medicine, they'll thank you personally upon meeting them the day they become healthy again, or send a letter talking if you haven't met them that day about how you saved their life. The sheer gratitude in it is what really makes it touching.
Toy Day is very cheerful and heartwarming holiday all around—Jingle wants to make things more exciting for your villagers and enlists the help of your player character dressed as Santa to deliver the presents. And it's just so darn sweet to see how overjoyed your villagers are to meet "Santa", with even the Cranky villagers acting like children, especially when you give them the right present they asked for. Another thing that adds to the heartwarming factor is when your villagers will wave goodbye to you after you give them a gift and leave their house, because what makes it different from usual is that they think they're waving goodbye to Santa.
If you then return to a snooty villager after the Toy Day event is completed, if you had successfully delivered the correct item to her when you talk to her, she may explain that the player looks too young to look like Santa, before pondering if it was the player that was Santa or the player asked Santa personally to deliver the item. She will then say that Santa or not, she is glad regardless before thanking you.
Even the fortune cookies in New Leaf get their share of heartwarming moments. Fortune number 36 is one of the very best:
Fortune number 33 comes close. The prize it contains are Pikmin.
"Value the friends you have, for one day you may need them."
On Valentine's Day in New Leaf, the game starts out with Isabelle asking the player if he or she got something for "a special someone". Isabelle then says she made some sweets but she "won't say who they're for". Then when you start up your save file, a letter from Isabelle arives in your mailbox with a chocolate cake attached. So really, the sweets were for the player all along.
What's more is if you give the cake to Dr. Shrunk. He actually has special dialogue for it.
Dr. Shrunk: A chocolate cake? I love these so much!
Speaking of Shrunk, you can talk to him at the coffee shop and he says something along the lines of "Because of you letting me open my club, my family's been better. Every day, we say thanks to you and Isabelle at the breakfast table.".
Also, at the same time, the villager who is the closest to you will send you a letter wishing you a Happy Valentines Day.
Each personality type, once befriended, has their own heartwarming style of interaction with the player:
Smug types adore the player character. Their flirtations are usually more funny than anything else, and they can start out saying something romantic and then shooting themselves in the foot...but in more day-to-day interactions, they can be incredibly sweet. Smug villagers may come bounding up to you with a relieved "There you are, (player name/nickname)!" or start a conversation with a compliment. Their letters often signal how much the player character means to them.
The Uchi characters (as mentioned above) are fiercely protective of the player, and will write you letters telling you that they know you've always got their back, and that you're the best person they know.
Lazy types may write you a panicked letter telling you about a nightmare they had, in which your character vanished from the town. They conclude the letter begging you to stay with them forever.
Snooty villagers are masters of the backhanded compliment, and more reticent than the other types...but every now and then, they will give you a present and thank you for continuing to be their friend "despite how...picky I can be at times."
Cranky types will check up on the player character like a father or older sibling. Their letters often start by grumbling before tapering of into a comment on how dependable your character is (before telling you not to speak about the letter to anyone).
Normal types have warm personalities from the get-go. When visiting your house, they will often compliment you on it, mentioning that no matter how you decorate, your home always feels warm and welcoming to them.
Jock types are the cheerleaders of the bunch. Their letters usually contain messages of encouragement. Beat them at hide-and-seek, and they will gush at your skill.
Whenever you get a villager's picture. (Although, there are some cases when you receive their picture in a goodbye letter upon their departure...)
Anytime Phineas shows up in your town to give you a new badge. He always says something positive about your accomplishments aligned with the badge you're receiving, whether it's saving up tons of bells, refurbishing a certain amount of furniture, or filling up your encyclopedia of bugs and/or fish.
The player may notice that K.K. is selling his music in the stores (when upgraded) when it's not like him to do that. It's explained in Happy Home Designer: he donates the money he earns to the kids. Good on you K.K.!
Blathers the owl's heartfelt appreciation for everything you donate to the museum, especially when you complete a collection. He's almost speechless with thanks when you give him the ultra-valuable stringfish.
The Welcome Amiibo update adds 50 villagers that were previously only in e+ or the Gamecube Animal Crossing, like Paolo, Rex, Sandy, Claude, Ketchup, and Spike.
When convincing a Normal villager to not move, if successful, the Normal villager may say that she kept hearing a voice inside her head telling her "Don't go." She then says she knew it was your voice. This is even more heartwarming if you first picked the option that would make her move and then successfully convince her to not move afterwards.