Cake is an item gifted to the player in the Animal Crossing series. It is usually given out on the player's birthday, either by their mother or by another Villager. However, in New Leaf, Cake is instead mailed to the player by Isabelle on Valentine's Day.
In Animal Crossing
On the player's birthday, the player will find a letter in their mailbox from Mom, which includes a Birthday Cake inside. However, this item can't be eaten; it can only be displayed in the player's house.
In Wild World
On the player's birthday, the player themselves will receive a birthday cake from one of their villagers, which can only be displayed once again, when they start the game on the day that is assigned as their birthday.
In City Folk
Like Wild World, the player is presented with a cake on their birthday by a villager. In City Folk, however, the player finally has the option to eat the cake. If they do, they will blush and flowers briefly blossom from them.
In New Leaf
In New Leaf, the concept of the player getting Cake on their Birthday was entirely removed; only having the player's cake on display as an inedible and unusable item at the player's party, and replaced with the player getting a Chocolate Cake from Isabelle on Valentine's Day instead. The Chocolate Cake received from Isabelle can be eaten.
However, there are a few ways to receive edible cake, such as through Streetpass. The birthday cake item can be received on the player's birthday and it can be eaten.