The Happy Mask Shop is located in Hyrule Castle Town Market, to the right of the path to the castle. The shop itself does not sell masks; rather, it lends them to aspiring individuals for sale. If a mask is sold, you pay back the price of the mask but get to keep any extra rupees, and are granted access to a newer mask model to sell. You can borrow masks you have already sold again; however, you can sell each model of mask only once. Masks are event items, and you can carry only one mask at a time. To see if someone is interested in purchasing a mask, talk to them while wearing it.
Wearing masks while speaking to people can elicit different responses.
Keaton Mask - This popular mask is modeled after the wily keaton fox.
Skull Mask - This monstrous mask will make you look like a Skullkid.
Spooky Mask - This scary mask is similar to a Re-Dead's face.
Bunny Hood - Some people believe that this set of bunny ears will make you run faster and jump higher.
Goron Mask - A mask that looks like a Goron.
Zora Mask - A mask that looks like a Zora.
Gerudo Mask - A mask that looks like a Gerudo.
Mask of Truth - A mask that can obtain hints from Gossip Stones and read people's inner thoughts.
Spoiler warning!
You might want to skip down to the next heading if you do not want facts about the game's storyline or plot revealed to you.
Any time you have a new mask, drop by the Forest Stage. From the Goron Village entrance, take a left. You'll see a pool of water ahead. Take a left. Take another left. Here you find a meadow with a couple of Business Scrubs. There's a tree at the back. There to the left of the tree is a group of butterflies hovering around the same general area. Walk around this area until you fall through a hole. You've arrived at the Forest Stage.
Put on a mask and approach the front of the stage (the raised portion with the sign on it). Many scrubs will pop up and dance around you joyfully. Walk over to a larger Scrub on the right. He will reward you with something, depending on the mask you are wearing.
Before you turn into Adult Link for the first time, use the Mask of Truth at the Forest Stage. There is a glitch in earlier versions of the game that stops the Deku Nut upgrade. However, if that is the case and its too late, consider that an optional upgrade and NOT EXACTLY NEEDED FOR A 100% COMPLETED GAME!