Snake Block
From the Super Mario Wiki
Snake Blocks are Blocks found in Super Mario World and New Super Mario Bros. In both games, they are a set of blocks that start out as a normal platform. But, when Mario or Luigi step on them, they begin to move. These blocks are special, due to the fact that they can move up, down, left, or right, in a way that is similar to a snake's movement. Mario must continue to move when on these blocks, or else he will fall off the Snake Blocks. Snake Blocks are mostly found in areas where it's needed to surpass risky obstacles like traveling over lava, or a large gap in the floor.
