Sand Mario can turn into a twister (as depicted), by spinning the Wii Remote once. Spinning again makes the mustached plumber turn back in his sandy appearance. Mario can also walk safely on quicksand and can actually merge with a pile of sand by ducking.
The first (and currently only) appearance of Sand Mario is in Super Mario Galaxy 2.5. The Power-Up needed first appears in Dusty Stream Galaxy in the mission, What a Wind E. Storm, where it is used to battle King Wind E., a giant Tweester. He must use his power to push King Wind E. into a sink hole (which all quick sand is sucked in). Sand Mario must be careful not to fall into one himself.