Bomp

Sliding Stones (also known as Pushy Walls) are a sub-species of Thwomp that first appeared in Super Mario 64. They are living, pushing, protruding stones that act as obstacles in many games.

Super Mario 64 / Super Mario 64 DS
Sliding Stones made their first appearance in Super Mario 64 and its Nintendo DS remake Super Mario 64 DS in the course Whomp's Fortress. At the beginning of the course, they go through a pattern of pushing, trying to shove Mario off a cliff and to his death. They also appear in other levels, such as Lethal Lava Land. The beginning and end Sliding Stones in Whomp's Fortress are thinner than the center Sliding Stones. Their eyes have a blue outline with blue pupils. The thick outline around the eyes gives them the appearance of protruding outward. In Super Mario 64 DS, the eyes were removed.

Super Mario Galaxy
Sliding Stones also appear in Super Mario Galaxy but with a different, more Thwomp-like look and face. They first appeared in Buoy Base Galaxy and later appeared in the Freezeflame Galaxy.

Super Mario Galaxy 2
In Super Mario Galaxy 2, they appear with the same role and appearance as in Super Mario Galaxy. They appear in the Fluffy Bluff Galaxy and the Throwback Galaxy, which is a remake of Whomp's Fortress. In the Fluffy Bluff Galaxy, Sliding Stones can assist the player in climbing the slope where they are located, but in the Throwback Galaxy, their purpose is more like that of an obstacle.