In the update 27.7.X.13, April 2017, a brand new Easter Event has been implemented in Realm of the Mad God. Now the Leprechaun Chase Event has been officially removed and the brand new Easter Event has begun.
In a Realm, instead of the Event starting right after a new realm appears like the Leprechaun Chase Event, after all the Ghost Kings have been defeated, the Easter Event will start. Quests will appear where the hidden eggs are located and the goal is to destroy them all. After all the Easter Eggs have been destroyed, a speech will appear in the chat.
This indicates that the Giant Egg has appeared in the realm. Unfortunately this egg does not show on the quest which makes this job a little tedious at times. However, it is mostly located between Highlands and the Mountains. When the Egg is found you will have to break it just like the Oryx Chicken. Once it is cracked the quest will appear for those who have not yet found the egg.
Once the Giant Egg has cracked, an Easter-Exclusive boss called Biff the Buffed Bunny will emerge. This is not an easy boss to fight so usually you want to have a decent group of other players.