Bad Mole

Bad Moles are recurring obstructions in the Legend of Zelda series. These small, red, smiling blocks usually group together to block Link's progress in a dungeon. They are usually only found within the confines of a building or dungeon.

The Legend of Zelda: A Link to the Past
Bad Moles can be found in various dungeons after the Palace of Darkness. After obtaining the Magic Hammer, Link will be able to smash Bad Moles, allowing him passage to whatever they were blocking. Smashed Bad Moles will stay depressed until Link exits the area.

The Legend of Zelda: Four Swords Adventures
Bad Moles are typically found in stages that take place in a dungeon or on the inside of a building. They also can be depressed with the Magic Hammer.