Door Mimic

Door Mimics are obstacles that appear in a few The Legend of Zelda games, and first appear in The Legend of Zelda: Ocarina of Time. Door Mimics have the same appearance as doors within a dungeon, although if Link approaches a Door Mimic, it falls down. If a Door Mimic lands onto Link, he is crushed by its weight and takes damage. Door Mimics can be destroyed from various weapons, such as bombs.

The Legend of Zelda: Ocarina of Time
In The Legend of Zelda: Ocarina of Time, Door Mimics appear in the Fire Temple, the Gerudo's Training Ground, and the Spirit Temple. Aside from bombs, Door Mimics can also be defeated by the Megaton Hammer. A rescued Goron in the Fire Temple gives this advice to Link.

Link can identify Door Mimics from close by. Unlike actual doors, which are installed in existing doorways, Door Mimics simply stack up against the wall, therefore protruding slightly. Door Mimics also have a fake handle painted on their frames. Door Mimics can also be identified by checking the Dungeon Map, which only shows the placement of actual doors but not Door Mimics.

The Legend of Zelda: The Minish Cap
In The Legend of Zelda: The Minish Cap, Door Mimics are found in Royal Valley and Dark Hyrule Castle. Their appearance has changed to a red door with a large keyhole. Door Mimics are a mechanical trap, which is shown because after a Door Mimic falls on the ground, a chain pulls it back into position.