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.
Answer: Because the Kokiri don't age past a certain age, but they do age up to that age. Link looked roughly the same age as the other Kokiri when his adventure started, which is why they never noticed that he was different.