Exclamation Mark Block
From the Super Mario Wiki
Exclamation Mark Blocks, also called ! Blocks, are floating blocks found in Super Mario World. At first all the player can see is Dotted Line Blocks, which is their outline, but after Mario or Luigi hits one of the ! Switches at the Switch Palaces, they become solid. Additionally, some Exclamation Mark Blocks contain various power-ups. Yellow blocks contain Super Mushrooms, and green blocks contain Cape Feathers. The red and blue blocks contain nothing and can be used as platforms.
In Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, and Yoshi's New Island the Dotted Line Blocks would temporarily become solid Exclamation Mark Blocks after a nearby ! Switch is pressed, allowing Yoshi and the baby riding him to use them as platforms.
In Super Mario 64, Exclamation Mark Blocks come in four different colors. Orange ones contain Coins, Power Stars, 1-Up Mushrooms, or Koopa shells. Red ones contain the Wing Cap, the blue ones contain the Vanish Cap, and the green ones contain the Metal Cap. All ! Blocks (except the orange variety) must be activated by hitting the corresponding ! Switch. If the switch isn't hit yet, the red, blue and green Exclamation Mark Blocks will be transparent and therefore cannot be hit. In Super Mario 64 DS, all Exclamation Mark Blocks, except for the orange variety, were replaced by red ? Blocks. The orange variety retains its contents from the original game, though Power Stars are no longer found within them.
A few Exclamation Mark Blocks also appear in Mario & Luigi: Superstar Saga and Mario & Luigi: Partners in Time. They have various functions and can activate events. Purple-colored Exclamation Mark Blocks are introduced in these games, which have varying effects. Three special Exclamation Mark Blocks in Mario & Luigi: Partners in Time are used to create three giant Exclamation Mark Blocks on Yoshi's Island and destroy giant Exclamation Mark Blocks of the same color in Thwomp Volcano, allowing the Mario quartet to traverse further down the volcano. The blue variety later appears in the Star Shrine, where it would change color depending on whether Baby Mario or Baby Luigi hit it.
Exclamation Mark Blocks can also be seen as part of the treasure hoard inside the safe in the Mario Party minigame Key-pa-Way. One of the Exclamation Mark Blocks is purple. Also, in the Mushroom Bank, the safe that keeps the items bought from the Mushroom Shop resembles a red Exclamation Mark Block.
Exclamation Mark Blocks also appear in Super Princess Peach, where they each contain a trapped Toad that needs to be rescued. There are three in each level and each Toad needs to rescued in order to complete the game. The Toad's cry for help can also be faintly heard when near the block.
Several Exclamation Mark Blocks appear in the Super Mario-Kun, where their role reflects whatever the volume is adapted from. In volume 16 of the Super Mario-Kun, which is based on Super Mario 64, they give him power-ups the same as in the game.
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