You may have see dotted-line "blocks" throughout the game. These "blocks" have no use in the beginning. However, if you activate a Switch Palace of the corresponding color, the dotted-line "blocks" will become solid exclamation blocks, allowing you to use them. Switch Palaces can only be completed once.
You can find the four Switch Palaces in the following worlds:
- Yellow Switch Palace (Yoshi's Island)
- Green Switch Palace (Donut Plains)
- Red Switch Palace (Vanilla Dome)
- Blue Switch Palace (Forest of Illusion)
The yellow exclamation blocks will provide Super Mushrooms, the green blocks will provide Cape Feathers, and the red and blue blocks only act as barriers.