Mole

Moles are strange creatures that act as obstacles and appear in dungeons and caves of and. They first appeared in the Palace of Darkness.

Characteristics
In both A Link to the Past and Four Swords Adventures, Moles look a lot like Whac-A-Mole, residing in small holes in the ground and bouncing up and down. Moles do not actively cause damage to Link, and simply block his progress. They appear in caves and dungeons, their faces locked in constant laughter, and impede access to certain areas. The only way to bypass a Mole is to hit it with the Hammer, which squashes Mole into the ground and allowing Link to get past.

Trivia

 * Beings very similar to Moles seem set to appear in The Legend of Zelda: A Link to the Past 2. In this game, they behave the same as before, but now pop back out of their holes after a certain time, propelling Link to higher areas if he is standing on them. Bigger Moles also appear that allow Link to bounce up to an entirely new floor.