Blue switch (Super Mario Galaxy)

A Blue Switch is a switch that appears in Super Mario Galaxy 2, usually during levels with unusually fast-moving obstacles. During gameplay, Mario or Luigi must Ground Pound them. Once Ground Pounded, the entire screen will turn black and white with a rippling effect, and the music will sound distorted, as if it were coming out of a radio. The main effect of hitting the switch, however, is that it will slow down all the obstacles around Mario or Luigi. They can allow them to pass under a Thwomp or jump on a fast-moving platform with ease. The switches only last for a few seconds though, so the player must move quickly to make it through the level in time. Blue Switches appear in only four galaxies: the Space Storm Galaxy, the Clockwork Ruins Galaxy, the Upside Dizzy Galaxy, and the Stone Cyclone Galaxy. However, the Blue Switch is used to change the flow of gravity in the Upside Dizzy Galaxy.

Trivia

 * In a pre-release version of Super Mario Galaxy 2, an earlier version of a Blue Switch was shown as a sort of "side-flipping" switch, as opposed to looking more like a ! Switch.
 * Sentry Beams' lasers, Amps' electricity, Electric Fences, Water Shooters' bubbles, Coins, and Mario or Luigi don't turn black and white when a Blue Switch is pressed.