World 7-2: Find Light-Blue Yoshi Egg
From start, go right and enter the castle. Walk right and shimmy down the first chain, which allows you to go downward. Continue down through the Mushroom Blocks and enter the door at the bottom. Walk right, go through the door, then walk left and grab the potion. Walk back to the right, and throw the potion near the upper-right pillar. Enter Subspace to grab the Light-Blue Yoshi Egg.