Marshmallow Block

From the Super Mario Wiki

A Marshmallow Block is a type of block that appears in Wario World in the sublevels beneath Wooden and Steel Trapdoors. They make the challenge of completing the sublevel more challenging. This is because they disappear almost immediately once touched, meaning Wario must be careful he does not fail to reach the next platform.

They can be considered a more dangerous form of Drop Block.

Blocks

! Block | ? Block | ♪ Block | 4-Bros. Random Block | Arrow Block | Aurora Block | Black Block | Blue Coin Block | Bonus Block | Brick Block | Bros. Block | Coin Block | Command Block | Control Block | Dice Block | Dotted Line Block | Drop Block | Egg Block | Event Block | Expansion Block | Giant ? Block | Giant ! Block | Grab Block | Green Block | Heart Block | Hidden Block | Hint Block | Ice Block | L Block | Laser Block | M Block | Marshmallow Block | Metal Block | Minus Block | Mushroom Block | Perry Block | Pink Block | Plus Block | POW Block | Pushing Block | Rally Block | Random Block | Red Block | Rock Block | Save Block | Shine Block | Simu-Block | Spin Block | Star Block | Stone Block | Super Block | Triangular Block | Turning Block | Used Block | Warp Block | Wooden Block | Yellow Block | Yoshi Block