Crouch
The crouch or duck move has been used in almost every Mario platformer made. To use it, the player must simply press 
or 
/
/
. If the player releases or //, he or she will go back to standing position. It is used to duck under projectiles and slide under walls while in motion. They can chain it to a Somersault; Super Mario Sunshine is an exception, as Mario can perform a Somersault, which is a crouch-related move; however, he can't crouch himself. If Mario or Luigi use it at the same time as a jump in side-scrollers, they will still crouch, but while in the air. This can be utilized to get in small holes. It can also be used when under a thin hole to move slightly with each jump. If the player is under a thin hole and releases the down button, the character performing it will automatically go towards the opposite direction the character is facing. It is not possible to crouch as Small Mario, but they can in Super Mario Bros 2, Super Mario World, New Super Mario Bros., and New Super Mario Bros. Wii. Also in Super Mario Bros. 2, if the player stays still in crouch position for a small period of time, the player will start to flash and be able to jump higher for one time. This ability is called the Power Squat Jump.
In some games, such as Super Mario 64 and Super Smash Bros. Brawl, attempting to move while in a crouch allows the character to crawl. This generally has no advantage.
