Bunny Link

is a form of Link in, appearing as a fluffy pink rabbit wearing a green tunic. Link is transformed into this form as a result of entering the Dark World, which changes people to reflect their true nature. Although it is never elaborated why, Link may have become a bunny as he has the gentle nature and compassion of a rabbit.

In this form, Link is completely defenseless and cannot use any of his weapons or his shield. He can retain his original form after obtaining the Moon Pearl from the Tower of Hera.

Transformation
When Link climbs Death Mountain on his quest to find the three Pendants of Virtue, he finds a portal in the north-east side of the mountain that teleports him to the Dark World's counterpart. Without the Moon Pearl, Link finds himself transformed into Bunny Link. A Bully and his Friend nearby explain to him how the world transforms anyone who enters in reflection of their true nature. Once Link obtains the Moon Pearl from the Tower of Hera, he will no longer transform into Bunny Link whenever he enters the Dark World.

In certain Dark World dungeons, Link can temporarily be transformed into a rabbit regardless if he has the Moon Pearl by coming in contact with rotating, golden star-shaped objects called Rabbit Beams. However, this change wears off after a few seconds or after being hit by an enemy.

Theory
Some people believe that this transformation has some correlation to Wolf Link from. They believe that Link is transformed into a wolf because a wolf accurately reflects Link's heart. Instead, the chosen hero who has been selected by the Gods will transform into a divine beast upon entering the Twilight. 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.

Trivia

 * Even when Link obtains the Blue or Red Mail, his rabbit form will still wear a green tunic if he is transformed.
 * Ravio from may be a homage to Bunny Link, as his mask has a rabbit motif and he originates from Lorule, a land extremely similar to the Dark World.