Thwack

Thwack is an enemy in Mario & Luigi: Partners In Time. They attack by spinning over you then crushing you, or spinning around then charging at you. Who they attack and their weakness depends on their color. They can also turn yellow and break in half, causing two blocks to attack the Bros. When short on allies, they will summon more. They can also form a totem. The totem is only seen in Thwomp Volcano with the babies.

Later on in the game, there are upgraded versions called the Wonder Thwacks. The color scheme changes (pink ones are now red, green ones are now blue, but when they become yellow, it's the same pallette), but they still use the same attacks. However, they're quicker, and float higher when trying to crush you.