From the Super Mario Wiki
Ads keep the MarioWiki independent and free :)
A Ground-Pound Switch is a type of switch that appears in Super Mario Galaxy and Super Mario Galaxy 2. To use this item, Mario must Ground Pound it (hence the name). Upon pressing this switch, a variety of things can happen, mainly making Star Bits or Coins appear.
There are also timed Ground-Pound Switches, tree stumps which have similar effects, and grey Ground-Pound Switches that make walls fall down, making other areas accessible.
They are also shown again in Super Mario Galaxy 2, having the same functions like in the first game. There is also a new function for Ground-Pound Switches in this game. If Mario Ground Pounds one of the switches, the screen turns grayscale, and the environment and enemies on the respective planet slow down greatly. This new function appears in the Space Storm Galaxy, Clockwork Ruins Galaxy, and Stone Cyclone Galaxy, and is useful in avoiding stage hazards that would be impossible to dodge otherwise.
Also, Whomps have a similar switch on their backs. Activating the switch with a Ground Pound will defeat the creature.
A Ground-Pound Switch appears in Super Mario Odyssey, where it is found on top of a skyscraper in New Donk City. Ground Pounding the switch causes a platform to temporarily appear, allowing access to another building.
Names in other languages