Happy Mask Salesman

The Happy Mask Salesman is a character initially appearing in The Legend of Zelda: Ocarina of Time, though he would play a bigger role in The Legend of Zelda: Majora's Mask (note: he also appeared in The Legend of Zelda: Oracle of Ages and the Zelda manga). A notable characteristic of the Happy Mask Salesman, which is also an odd one, is that he continually smiles and never stops doing so, even when enraged.

Ocarina of Time
In Ocarina of Time, a title in which he didn't play a big role, he was stationed in the Happy Mask Shop. Here, he would give Link the chance to become what he is - a mask salesman. Fulfilling your role will reap you an attractive reward - the Mask of Truth.

Majora's Mask
In Majora's Mask, the Happy Mask Salesman was traveling Termina selling masks. He had a variety of different ones stationed on his backpack which jutted out, making it seem rather large. Among the masks he had was the sacred and dangerous Majora's Mask. Skull Kid, an innocent creature who had but just a couple of fairy friends, stole the appealing mask for his own. It corrupted him and caused him to summon the moon to crash into Termina. Majora's Mask was simply using the kid as a puppet, and would've done so to anyone who donned the mask.

Meanwhile, Link, who was transformed into a Octorok due to the possessed Skull Kid's trickery, met up with the Happy Mask Salesman. The salesman returns Link to his human form by teaching him the Song of Healing, only if he promised to retrieve the mask which was stolen from him.

The Happy Mask Salesman in Majora's Mask has an odd demeanor. As formerly mentioned, his smile never vanishes - though he may occasionally after conversing with Link. When talking, he'll automatically alter his position without going through the physical act of doing so. He teaches his songs to Link via a large organ. His personality have caused him to become quite popular among Zelda fans.

Oddly, while inside the moon in the end of the game, there are a multitude of children who bare a resemblance to the Masked Salesman. After talking with them, they'll reveal that when older they'll actually become salesmen.