Keyhole
From the Super Mario Wiki
Keyholes are secret level passages in the game Super Mario World. Every level in the game that is represented by a red dot on the map has a secret exit; in most of these levels the secret exits are Keyholes. To reach the secret levels, Mario or Luigi must find a Key and bring it to the keyhole. Once the key is found by one of the brothers, they then will have to carry it to where the keyhole is located. Most of the time Mario or Luigi only has one chance to get the key and bring it to the keyhole. When the keyhole is activated by the key, the keyhole increases in size. The player will then go inside the Keyhole, along with Yoshi, if the player is riding him.
