The Egg Bundle is an item only accessible during the Egg Hunt Event. It contains 3 Eggs. It may contain a Golden Egg, which drops more Carrots than a Festive egg. You can watch a video to open all 3 eggs. There are 14 hidden Egg Bundles in the game, but you can get more by blowing up a special "bunny" Creep, or buy a large chest while the Event is active.