Granny's Potion Shop
When Link is a child, the only way for him to access the shop is by flying into the small yard in front of the shop by using a Cucco. However, the shop is closed and a message is posted on the door letting customers know that Granny is out in the field gathering herbs for her Potions.
Once Link returns seven years later, he can access the now-opened shop by using the Hookshot to grapple on to the roof or by using the back door of the Potion Shop. After Link delivers the blue Cucco Cojiro to the punk guy in the Lost Woods, he asks Link to deliver an Odd Mushroom to Granny. Once Link has delivered the Odd Mushroom to her, she comments on how the guy is a "bum" for going into the forest and asks Link if he sees him again to give him her most powerful potion she has created, the Odd Potion.
(Must have given the owner the Odd Mushroom
and successfully traded the Odd Potion)