Skull Kid

The Skull Kid is what becomes of children getting lost in the Lost Woods and appears in Ocarina of Time, Majora's Mask, and Twilight Princess. They first interact with Link in Ocarina of Time, and later a Skull Kid plays a major role in Majora's Mask. Skull Kids dress in a red cloak and hat covering an underlayer of clothing comprised of a straw-like material, and play a flute, which they can also use as a weapon to shoot projectiles.

Ocarina of Time
In Ocarina of Time, a Skull Kid can be found in the Lost Woods, in the area directly to the left of the entrance room. Whenever Link approaches, the Skull Kid will disappear from the area. To circumvent this, Link can befriend the Skull Kid by playing Saria's Song while standing on top of the stump across from the Skull Kid's position, and he will receive a Piece of Heart as a gift. Another two Skull Kids can be found in the area directly to the right of the entrance, where there is a mini-game in which Link repeats a sequence of notes on his ocarina to win a Piece of Heart. It is not known whether these are apparitions of the Skull Kid in the area on the left of the entrance, or separate Skull Kids entirely.

While Z-Targeting, Navi mentions that the Skull Kid seems unhappy to have no face. Upon first seeing Link wearing the Skull Mask, the Skull Kid comments that he would like it to make him appear a little tougher. Link is able to sell him the mask as part of the Mask Trading Sidequest, but the Skull Kid pays just ten rupees when the wholesale price is twenty, leaving Link to cover the difference.

It is said that non-Kokiri who enter the woods become Stalfos upon getting lost. However, there is speculation about whether or not Kokiri or Hylian children turn into Skullkids. It is more possible to believe that the Kokiri turn into Skull Kids, due to the fact that they stay children for their whole lives, but also Stalfos never appear within the Lost Woods.

If Link encounters the Skull Kid as an adult, he will be attacked with Deku Seeds shot from the Skull Kid's flute. Navi says that he is attacking because he does not like adults. If Link slashes him with the Biggoron's Sword or Giant's Knife he will collapse and disappear, leaving behind an orange rupee.

Majora's Mask
Prior to the events in Majora's Mask, the Skull Kid was befriended by the Four Giants. After a time, however, the Giants left Termina and the Skull Kid was alone, motivating him to seek attention by causing mischief and playing pranks on people.

Some time after, Skull Kid met with Tatl and Tael and stole Majora's Mask from the Happy Mask Salesman. By the time the events of Majora's Mask take place, the Skull Kid and his two fairy companions ambush Link and steal the Ocarina of Time. During this confrontation, the Skull Kid transformed Link into a Deku Scrub.

Over the course of the game, Link gathers the power of the Giants and frees the Skull Kid from the evil influence of Majora's Mask. During the end credits, the Four Giants reassure the Skull Kid of their friendship with him, and tells Link that he remembers befriending him in Ocarina of Time. The last scene shows a drawing carved on a tree trunk made by the Skull Kid himself, which includes Link, the Skull Kid, Tatl, Tael, and the Four Giants.

While Link first encounters the Skull Kid in the Lost Woods of Hyrule, dialogue in Majora's Mask suggests that the Skull Kid is possibly from Termina. During the ending sequence in Majora's Mask, the Skull Kid mentions to Link that he has the same smell as the "fairy kid" who taught him a song in the Lost Woods. This suggests that the Skull Kid is the one by the tree stump near the bridge in the Lost Woods in Ocarina of Time, meaning he's the one that the young hero sells the the Skull Mask to. This would make sense since this shows his fondness for intimidating-looking masks.

His skin appears to be made of wood and he has a duck-like beak.

Twilight Princess
In Twilight Princess, the Skull Kid leads Link through the Lost Woods portion of the Sacred Grove until he reaches the resting place of the Master Sword. Along the way, the Skull Kid plays a cruel game of hide-and-seek with Link, and Link must find him several times before he will lead him to where he needs to be.

When Link returns to the Sacred Grove area later in the game, the Skull Kid will help him navigate the Lost Woods a second time, this time leading him through different areas to take him to the Temple of Time dungeon. His hiding spots will be more difficult to find. However, two factors give away his location: the light of his lantern and the sound of his instrument playing Saria's Song. Although the Skull Kid never physically attacks Link, he will summon Puppets to do the job. Every time he is hit in battle, he will summon more puppets, but he can be beaten quickly with the bow and arrows. After defeating him the second time, he will tell Link that was fun and vanish.

One may note that his eyes and face look very similar to those of the Moon from Majora's Mask, although with a mischievous smile instead of the Moon's trademark scowl. Due to the fact that he knows Saria's Song, it is possible that he is the same Skull Kid from Ocarina of Time and Majora's Mask. Strangely enough, the horn with which he plays the aforementioned song bears somewhat of a resemblance to Deku Link's Pipes of Awakening both in its appearance and sound. The lantern he carries is also similar to that held by Poes.

Trivia

 * Skull Kid shares many similarities with the Flute Boy from A Link to the Past: both are kids that play music with a flute in the woods and that disappear when Link approaches them. The Flute Boy may have served as a prototype or concept for the Skull Kid.
 * Skull Kid's instrument from Twilight Princess resembles a modern version of the Deku Pipes from Majora's Mask.