A Green Egg Block
An Egg Block is a type of block appearing in Super Mario World 2: Yoshi's Island, Yoshi's Story and Yoshi's Island DS. When hit, they release eggs for Yoshi to throw at his enemies. In Yoshi's Story, the color of the spots on the Egg Block is the same as the color of the Yoshi being used and will also release up to 6 eggs of that color.
Egg Blocks make a cameo in Super Mario Sunshine, appearing in the "secret" levels as blocks Mario could jump on while making his way towards a Shine Sprite. In Yoshi's Woolly World, they contain yarn.