An Easter Egg is a person, place, or thing that is hidden or not in the game that can be funny or profitable. Some of the games that the Animal Crossing Series related to so far was from Nintendo Consoles, to Mario, the Legend of Zelda, Metroid, Pikmen, and Star Fox. These are not exactly an easter egg, but in Fortune Cookies, you can turn the fortune in after you ate it to Timmy to recieve an item from any of the featured items from any Nintendo related games from the description and with the number on it.
New Leaf Easter Eggs
Mario Mega Mushroom
In New Leaf, if you eat a Famous Mushroom, the Player will grow big for a couple of seconds. After that, the Player will start shrinking back to normal size. This is a reference to Mario, where when he eats a mushroom, he will grow much twice his size.