Skull Kid
Skull Kid
Skull Kid is the primary antagonist of the game. With the power of Majora's Mask, he causes a series of disturbances and disasters that plague the different regions of Termina. Three days after Link’s arrival he will cause the moon to fall, resulting in the complete destruction of Termina.
History
Skull Kid's origins are unknown. However, it can be deduced that he is the same imp from the story of the festival's background. That story mentions a childhood friend of the Four Giants whose friendship predated the creation of the four worlds that surround Termina. However, when the giants decided to leave to their respective areas, the imp felt abandoned and terrorized the citizens of Termina as a result. The giants returned and threatened to destroy him if he didn't leave the human world. To the imp, this marked the end of their friendship.
Tatl reveals that Skull Kid had also been fighting with his friends when she and Tael found him. The existence of the Four Giants as well as the dialogue they share with Skull Kid after the defeat of Majora's Mask further supports the idea that he is the imp from the story.
In addition, Skull Kid as shown this game is indeed the same Skull Kid encountered in the Lost Woods in Ocarina of Time. This can be confirmed by dialogue in the ending of Majora's Mask:
"Eh-hee-hee...you have the same smell as the fairy kid who taught me that song in the woods..."
The song he is referencing to is Saria's Song, which you teach the Skull Kid in Ocarina of time in order to gain a heart piece.
Prior to Day 1
Skull Kid's actions before Link's arrival set the events of game in motion. Always the trickster, he ambushed the Happy Mask Salesman just as he would later ambush Link. Regrettably, Skull Kid stole Majora's Mask from the salesman. Upon putting it on, the evil that resided in the mask began to change and control him. Link learns throughout the three days that Skull Kid is responsible for many atrocities, including the hex on Kafei and the damage to the Great Fairies. By the time Link encounters Skull Kid, the imp harasses and abuses his best friends Tatl and Tael.
Day Four
At the end of the game, it is revealed that he was friends with the Four Giants when they lived among the people. When they departed, Skull Kid developed feelings of abandonment and resentment which were amplified after he stole Majora’s Mask from the Happy Mask Salesman and succumbed to its corrupting influence. After being freed from the mask, Skull Kid finally understood that his friendship with the Giants never ended and they would always be there if he needed them.