Bunny Link
alroel
In A Link To The Past, Link transformed into a fluffy pink rabbit upon entering the Dark World, the former Sacred Realm turned dark due to Ganon's evil. This odd transformation happened until Link had obtained the Moon Pearl. He also experienced this transformation in other parts of his ALttP adventures, most often whenever he came into contact with rotating, golden, star-shaped objects.
Legends say that when entering the Sacred Realm, you take the shape of what your heart reflects. Link becomes a bunny becuase he has the timid compassion and kindness of a rabbit.
This "Bunny Link" transformation was the begining of a long history of Zelda game transformations, which include: Adult Link, Deku Link, Zora Link, Goron Link, Fierce Deity Link, Wolf Link, Minish Link, etc...
Some people believe that this transformation has some correlation to the Twilight Princess wolf transformation, Wolf Link. They believe that Link is transformed into a wolf because a wolf accurately reflects Links heart. More accurately, the chosen hero who has been selected by the Gods will transform into a divine beast upon entering the Twilight Realm. This legend was told to Link by Midna, who knew upon first seeing him that he must be the divine beast chosen to save her world.