Wart

Wart (ワート, Waato) is a Mini-Boss in Majora's Mask. It is a huge eye that rolls around trying to hit its enemies. At the start of the battle, Wart is hovering slightly above the ground, completely surrounded by a mass of bubbles, rendering it immune to any damage.

Strategy
Wart is a time-consuming enemy. The sheer amount of bubbles on it make it a long struggle to pierce its shield, as it is constantly moving, along with Wart, which will differentiate from retreating to trying to press itself against Link in an attempt to cause damage. The bow is not a good idea at this point, as there are simply too many bubbles. Any offensive weapon is capable of removing the bubbles, although the best is the bomb, which knocks many bubbles off at once. Using the Hookshot is another way of removing the bubbles, although it is a time-consuming way. The bubbles are incapable of being destroyed while on Wart, only knocked off, which makes them even more of a pain. When an opening is finally made, and Wart's eye is no longer blocked by bubbles, the bow is the way to go. After enough shots, Wart will enter stage two, forcing its surviving bubbles off its body and begin rolling around wildly. First finishing off any bubbles, then attack Wart with the bow. After a few more shots, Wart will be finished.

Trivia

 * Wart also has a resemblance to Arrghus, and Vitreous, who you kill in the same manner. Arrghus also shares Wart's name in the Japanese version of A Link to the Past.
 * A frog-like character named Wart also appeared in Doki Doki Panic (or, Super Mario Bros. 2). This character differed drastically from the Wart of Majora's Mask. Interestingly, this Wart made a cameo appearance in Link's Awakening, with his Japanese name Mamu Mamu.
 * The Deku Toad from Twilight Princess bears some similarity in the way it acts to Wart, a mini-boss of the Great Bay Temple. Like Wart, it has many eye-like objects on its body (though these are actually its eggs), but not nearly as many as Wart did. It also starts the battle on the ceiling, like Wart. Interestingly enough, the final boss of Super Mario Bros. 2 is a giant toad named Wart.