How to Find the Smell in The Ocarina of Time

Turn on your game console and load "Legend of Zelda: Majora's Mask."

Complete Woodfall Temple if you have not already. Once you've completed the Temple and saved the Deku Princess you will return to the Deku Palace. After watching the cut scene speak to the Deku Butler -- a tall Deku in a butler uniform. He will inform you of a challenge in the Deku Shrine to the left of the Deku Palace entrance.

Exit the Deku palace and turn right. Use the lily pads to get across to a previously blocked Deku Shrine. Enter the Shrine and speak to the Butler. He will challenge you to a race. Accept the race and follow him as closely as possible -- you will never overtake him but if you manage to keep up with him he will reward you. Equip the Bunny Hood if you have it as it will make you run faster.

Speak to the Butler once you've reached the destination and he will reward you with the Mask of Scents -- a pig-like mask. With this mask you will be able to "see" smells.

Return to the Southern Swamp and go to the Magic Hags' Potion shop. In the Woods of Mystery behind the shop you can use the Mask of Scents to "see" the smell of Magic Mushrooms which you can scoop up into an empty bottle and sell to the aforementioned Hags for 40 rupees each. The smell will appear as purple smoke which you follow to the source of the mushrooms. Once you've sold the Magic Mushroom to the Hags they can sell you the blue potion -- a potion which cures you of the status curse inflicted by Blue Bubble attacks.