In the stage, "Find my egg!" look for a bubble in the celing at the top of where you start, then, hit it and a rumbler will appear asking if you want to participate in the "Egg Rumble Mania!"
Jack Egg: Complete game once
Queen Egg: Complete game twice
King Egg: Complete game and unlock every mini-Game
Giant Egg: Beat the game with 6 stars
Mini-Egg: Beat the game with 7 stars
Twin Egg: Beat the game in a gameplay status of 3 hours