Blue Switch is an object in Mario & Luigi: Partners in Time. It has four blocks on it, symbolizing that when all four bros. are on top of it, it will go into the ground, and open up any passageways or make any changes. They are found throughout the game, in every level. It has one variation, the very rare Yellow Switch.
Blue Switches also appear in the Paper Mario series. Blue Switches are one-time use switches that activate an important change in the environment, such as a bridge being built or a staircase appearing. If one is present in the environment, it is needed to be jumped on to move on through the level.