Although the castle’s guards keep most enemies at bay, there are a couple of puzzles in the vicinity of the castle that Link must solve to continue on his quest.
Malon's Dad
Malon of Lon Lon Ranch needs Link’s help to find her dad. She said he went to the castle to deliver some milk.
The Sleeping Man
Even after sneaking past the castle guards, Link’s way into the castle will be blocked by a sleeping man in blue overalls and a red shirt. He must figure out a way to get this big lazy oaf out of his way.