Cloud Block

A Cloud Block is a semi-solid block mainly used as platforms for bonus areas above the ground. They first appeared in Super Mario Bros. in World 2-1, in the bonus area accessed by hitting the secret beanstalk halfway in the level. Cloud Blocks strongly resemble Lakitu's Cloud.

Super Mario Bros.
In Super Mario Bros., Cloud Blocks appeared in World 2-1, in the bonus area reached by hitting a Brick Block with a beanstalk. Unlike in later games, the Cloud Blocks in this game are solid.

Super Mario Bros. 3
In Super Mario Bros. 3, Cloud Blocks first appeared in the sky in World 1-1, reached by flying to the top of the level with a Super Leaf. From this game onwards, Mario can pass through them from the bottom.

Giant Cloud Blocks also appear in World 4.

Super Mario World
In Super Mario World, Cloud Blocks first appeared in Yoshi's Island 1, where they were used to transport a 1-Up Mushroom to Mario or Luigi.

Super Mario Maker / Super Mario Maker for Nintendo 3DS
In Super Mario Maker and Super Mario Maker for Nintendo 3DS, Cloud Blocks have a new design for the New Super Mario Bros. U game style. Cloud Blocks can be destroyed by Thwomps, Bowser in Super Mario Bros. 3-styled levels, and Skewers.

Super Mario Run
Cloud Blocks appear in Super Mario Run, where they are platforms in Bullet Bill Barrage. As of version 3.0.4, they also appear as platforms in Remix 10's Cloud Bonus Courses.

Super Mario Maker 2
Cloud Blocks reappear in Super Mario Maker 2 as placeable course elements under the "Terrain" category.