Continuity mistake: When given to the guy running around Hyrule Field, the Rabbit Hood mask gives said guy super human speed when running on foot. Yet it gives nobody else such speed, not even Link who can wear it at any time.
Continuity mistake: During the scene where Link leaves the Kokiri Forest, as he runs across the bridge, the overhead shot shows him to be nearing the other side, but when Saria appears, and the shot changes, Link appears to only be halfway across.
Chosen answer: There is another thing it does for the player. Deep in the Lost Woods is an area with two creatures that will sell the player items. Look for where you see a bunch of butterflies gathered. Head toward them and you will fall into a hole. When you land put on the Mask of Truth and slowly walk forward. Some Deku creatures will pop out and look at you. After this talk to the big Deku creature to the right and he will increase your ability to hold more Deku nuts. Wearing other masks from the Happy Mask shop will also have different reactions from the Deku Scrubs.