Birthdays are celebrated in the Animal Crossing series by both the player and animal villagers of the player's town. They do not form an important part of the game, but add to the overall authenticity of the character's life. The player can choose their birthday when asked by a villager. This forms the first true conversation a player encounters in the game. Any date can be chosen for the player's birthday - if they select a date that is the same as the villager's in Wild World or City Folk, the animal will realise this and appear surprised.
Doubutsu no Mori and Animal Crossing
Unlike the player, villagers do not celebrate their birthdays. The player is sent a large, inedible cake from their mother, which can be displayed in their house. The player will also receive letters from villagers with presents and be greeted at the player's front door by another villager who will personally present a gift, often an NES game.
Animal Crossing: Wild World
- For a list of villager birthdays in Wild World, see List of villager birthdays in Animal Crossing: Wild World.
This is the first game in which villagers also have birthdays - the player can visit them in their house on that day, where they will be walking around their home with a fellow villager that they get along with, usually one of the same gender. The player can give any item to the villager that is celebrating their birthday for a gift, but this may cause the game to freeze. The two villagers in the room, if near to each other, may applaud and laugh. A player can tell if it is a villager's birthday by a letter sent by them in advance, and a notice that appears on the bulletin board on the day.
The player themselves receive a birthday cake which cannot be eaten, when they start the game on the day that is assigned as their birthday. The player will also receive a letter and a present from their mother.
Animal Crossing: City Folk
- For a list of villager birthdays in City Folk, see List of villager birthdays in Animal Crossing: City Folk.
Unlike in Wild World, villagers do not celebrate their birthdays, despite a notice on the bulletin board that congratulates them. Instead, a player can send the villager a letter on that day. The villager then thanks the player for wishing them a happy birthday in their reply.
As with Wild World, the player is presented with a cake on their birthday by a villager, which can be placed in the home or eaten. After eating, flowers briefly blossom from the player, much the same as the emotion "delight."
Animal Crossing: New Leaf
- For a list of villager birthdays in New Leaf, see List of villager birthdays in Animal Crossing: New Leaf.
When it's the player's birthday, a villager that has high friendship with the player will be waiting outside. The villager will then take the player to their house for a birthday party. They will shout Happy birthday to the player. During the party, if the player checks the birthday cake on the table, the player will be able to make a wish and blow on the microphone to blow out the candles. The villager that hosts the party will give the player a gift depending on how much friendship they have. The player may receive one of the following:
- Birthday Board
- Birthday Cake*
- Birthday Candle
- Birthday Hat
- Birthday Sunglasses
- Birthday Table
The host may also ask the player what they wished for, but it's up to the player if they want to tell the host. If the player visits K.K. Slider the Saturday before the birthday, K.K. Slider will sing "K.K. Birthday". He won't give the player a copy, but the following day, the player will receive it in the mail. 
Villagers also celebrate birthdays. If the player gives them a present, the next day the player will receive a letter from that villager. There's a chance that no birthday party will occur if the player time-travels too often or doesn't play for a long time.
Animal Crossing: amiibo Festival
If the month during which the game is set contains the birthday of one of the amiibo figurines. Special event spaces marked by a cake will appear on the game board. Landing on one of these spaces will award the player Happy Points — with the player whose amiibo's birthday is that month receiving the most points. In addition, villagers on the game board have random events for their birthdays.
Animal Crossing: Pocket Camp
Villagers will congratulate the player, but nothing special happens on the player's birthday. For example, they will not give presents to the player. However, there is special dialog if the player was born on a special day, such as a Leap Year, New Year's Day, etc.
Animal Crossing: New Horizons
- For a list of villager birthdays in New Horizons, see List of villager birthdays in Animal Crossing: New Horizons.
A week before the player's birthday, a notice will be posted on the Bulletin Board. On the day itself, Tom Nook or Isabelle will mention it in the public announcement. As the player leaves their home, they will immediately be greeted by one of their villagers. They will then be taken to that villager's house, which will have been redecorated with a birthday cake in the center. Two other villagers will be in attendance.
After blowing out the candles on their cake, the player will be given a stick and a piñata set up for them to beat. The piñata contains Birthday Cupcakes; the faster you hit it, the more cupcakes there will be. The player is then given an item from the Birthday Set and can enjoy the party until they leave the house, after which it returns to normal. When the player exits their house after the party, they will receive a Homemade Cake from Mom in the mail. Additionally, a Nook Miles Stamp called “Happy Birthday” will be unlocked.
The Birthday Cupcakes can be given to villagers (or another player) to receive a gift, kept as a decoration, or eaten, but they cannot be sold. Additionally, K.K. Slider will be outside of Resident Services, and he will perform K.K. Birthday. During the performance, birthday messages from the island's residents will flash on screen. Afterwards, the player will receive an aircheck of the song.
Villager birthdays are similar to player birthdays, except celebration is optional. They are announced on the Bulletin Board a week in advance and then by Tom Nook/Isabelle in that morning's announcements. If the player's birthday falls on the same day as that of a villager, both will be mentioned on the Bulletin Board and morning announcements. The villager's party will be in their home. Attending and giving a gift will boost the player's friendship with that villager, and they will send a thank-you gift in the mail the next day. Additionally, the player will earn a Nook Miles Stamp titled Birthday Celebration, which has 3 tiers.