Stalchild

Stalchildren are recurring enemies in the Legend of Zelda series. They are undead skeletal-like creatures that seem to be closely related to Stalfos, except more child-like and unarmed. Stalchildren seem to be nocturnal dwellers, as they are only seen during the night time, and when the sun rises, they immediately disappear.

In the original Japanese language versions of the games, Stalchildren are referred to as "Stalbabies" while the seemingly unrelated Skull Kid race are referred to as Stalchildren instead.

The Legend of Zelda: Ocarina of Time
Stalchildren relentlessly attack Link in Hyrule Field at night when he is a child. Strangely, they do not appear when Link is an adult, despite Ganondorf's complete dominion over Hyrule at this point. If Link walks on the small paths scattered across Hyrule Field instead of on grassy areas, Stalchildren will not appear. Also, they will not appear at all if Link wears the Bunny Hood. In a confrontation, they may be easily outrun, and are quickly defeated by Link's sword; however, if the latter tactic is used, more Stalchildren will inevitably appear.

When eleven Stalchildren have been defeated, a larger one appears, which despite its size, possesses battle attributes identical to its smaller brethren; the size of this larger Stalchild increases every time this process is repeated. Normally, the night in Hyrule does not last long enough to show the full extent of this effect, but a cheat device can be used to perpetuate the night, ultimately allowing a Stalchild larger than Captain Keeta to appear. Interestingly, Stalchildren will be instantly defeated if they come in contact with water; if Link stays near the river when Stalchildren appear, they may occasionally come in contact with water while stalking him, killing themselves.

The Legend of Zelda: Majora's Mask
Stalchildren were once soldiers of the Ikana army led by Captain Keeta. They persevere to serve the Ikana Kingdom and its royal family, even beyond death. After Link defeats Captain Keeta and receives the Captain's Hat, Stalchildren will mistake him for Captain Keeta while he wears the hat, and will follow his orders.

Link can order the Stalchildren found in Ikana Graveyard to open the graves for him. If he enters the grave they encircle on the First Day, he will eventually find a stone with the "Song of Storms" inscribed on it. Learning this song is crucial to advance in the game. On the other two nights, the graves will lead to a Piece of Heart and a bottle, respectively.

Stalchildren can also be found inside the Oceanside Spider House. Here, If Link is wearing the Captain's Hat, they give him tips about the house and help him solve a puzzle that leads to a Piece of Heart.

Theory
It is possible that the Stalchildren of Ocarina of Time are Kokiri who have left the Kokiri Forest, thus turning into Stalchildren. They could also be Hylians who are suffering the effects of the Lost Woods, with a Stalchild being an intermediary stage between a Hylian and a Stalfos. However, since the Stalfos transformation is supposedly imposed on those unable to find their way out of the Lost Woods, it seems unlikely that such individuals would appear in Hyrule Field. Additionally, Kokiri are seen outside the Forest during the end credits of Ocarina of Time, suggesting that their law of "Those who leave the forest will die" is simply a warning of the dangers posed by the outside world.