Sheik is a character from The Legend of Zelda: Ocarina of Time. He serves as Princess Zelda’s alter ego in the game; to escape Ganondorf’s capture, Zelda passes herself off as a male Sheikah known as Sheik. Throughout the course of the game, he aids Link, who is initially not privy to his true identity, by providing him with information and teaching himteleportation songs with a lyre.
His physical appearance and frequent usage of Deku Nuts as a means to vanish quickly is decidedly reminiscent of a typical ninja. Possibly owing to this, he has become a popular character in The Legend of Zelda mythos, despite currently appearing only in one game out of the main series. In the later games where she appears, she has a more feminine body figure.
In The Legend of Zelda: Ocarina of Time, Zelda disguises herself as a surviving member of the Sheikah clan under the name of Sheik. With voice muffled and face concealed, as well as wearing a form-fitting blue unitard with the red Sheikah eye in the center, Sheik is unrecognizable as Zelda. Sheik plays the lyre and teaches Link new songs to help him on his quest.
When Link arrives at the Temple of Time near the end of the game, she uses the Triforce of Wisdom and reverts to Zelda. It is revealed by the character’s trophy in the North American translation of Super Smash Bros. Melee that Zelda used her magical skills to change her skin tone, hair length, eye color, and clothing; it is revealed in the canonical officially licensed manga for The Legend of Zelda: Ocarina of Time that following changing her appearance, Zelda ordered Impa to seal her consciousness away for seven years, so that she may become Sheik and live incognito.
Sheik also returned in Hyrule Warriors, using a harp and shortsword in her attacks.