Stretch Shroom

Stretch Shrooms are a type of a Mushroom Platform found in New Super Mario Bros. series.

New Super Mario Bros. series
Stretch Shrooms first appear in New Super Mario Bros. They only appear in World 5-A, being blue Mushroom Platforms. They shrink and expand periodically, pulling anything on the ends of the platform to the center when they contract. In later games, they are pink.