After completing the Forest Temple, return to the Temple of Time. Drop the Master Sword back into the stone to change back to Young Link. Go to the mask shop and make sure Link can borrow the Bunny Mask. Link should also have the Giant's Wallet (that holds 500 rupees) for this trick to be most effective. Thirty Gold Skulltulas should also have been collected, and Link should have talked to one of the kids in the house in Kakariko Village that has the curse on them to get the wallet. Buy as much as possible with the current amount of rupees. Go to Hyrule Field and run to the right, towards Lon Lon Ranch. Run until a man running around like an idiot comes into view. Follow him until he sits down and gets tired. Wear on the Bunny Mask and talk to him. He will ask for the mask and fill Link's wallet with rupees.