Zirro is an enemy that appears within A Link to the Past.
Purple Zirro are found around the Ice Lake within the Dark World. These winged mushrooms hover around in certain areas until Link draws near. When Link is around, the Purple Zirro will fly in close proximity to Link, but still in somewhat of a random pattern. Purple Zirro have no means to attack Link other than simply flying into him. Fortunately this doesn't do much damage at all as it will take away just one heart from Link.
Purple Zirro are more of an annoyance than actually a difficult enemy. If Link tries to swipe at a Purple Zirro, it will immediately fly away from Link. This makes it rather difficult to defeat these enemies from up close, but it also makes it easy to repel them away from Link. Link can defeat these enemies with two strikes from the Master Sword. Link can also use projectile items such as the Bow and Arrow, in which it will also take two hits to defeat.