Rustling Grass

Moving Grass is a curious growth of grass found only in Majora's Mask which Link will find standing in groups of nine. The special thing about this grass is that after Link has cut one or more of them, the other ones will start to jump away. After a while it will, quite literally, destroy itself.

Wearing the Keaton Mask while disturbing the grass will cause a Keaton to appear.

This special grass can be found only at Milk Road, the Mountain Village, in North Clocktown, and in the grove at the beginning of the game.

Trivia
Moving Grass always drops one green Rupee when slashed. However, it drops nothing when it destroys itself. If all Moving Grass is destroyed in a single attack, it will also drop a red Rupee.