Rover

Smasher is the name of a mysterious round creature with dog-like behavior that appears as a recurring mini-boss in Link's Awakening and Oracle of Ages. To attack, it barks and pick up a heavy Ball to throw it at Link in an effort to incapacitate him. Link must reach the ball before he can and throw the sphere back at Smasher with his Power Bracelet, slamming the creature into submission.

Link's Awakening
Smasher is found in a hidden room in Face Shrine, in one of the "eyes" on the dungeon map. The only way to access this room is the open the wall with Bombs. After defeating Smasher a warp to the entrance of the dungeon will appear and Link can pass through to a room that contains a secret passageway deeper into the dungeon, but if he cannot find the passageway, the rooms will loop endlessly. Smasher later appears in Turtle Rock along with other mini-bosses, where it will continue to reappear even after being destroyed.

Oracle of Ages
Smasher is found as the mini-boss in the Crown Dungeon on Rolling Ridge. The only major difference from its Link's Awakening incarnation is that the ball will disappear after a short while after being thrown and reappear elsewhere.