Instructions
Speak with the Cuccoo Lady in Kakariko Village. As a child, you helped her gather Cuccoos, but as an adult, she will offer you the Pocket Cuccoo.
Wait for the Cuccoo to hatch. Use the bird in front of Talon, who you will find snoozing at Lon Lon Ranch. He will give you a rare Cuccoo named Cojiro.
Take Cojiro to the Forgotten Woods and show it to Grog, who is also taking a nap. He will give you an Odd Mushroom.
Deliver the Odd Mushroom to the strange woman in the Kakariko Village potion shop. You are not allowed to warp, but if you make it in time, the old woman will give you the Odd Potion.
Call Epona and head to Hyrule Castle Town. Enter the Temple of Time and return the Master Sword to its pedestal to become a child. When the animation completes, you will have the Odd Potion, however you are unable to use it and it will quickly expire.