Rare Item Shop
After you rescue Dyna & Mite, the man from the mine opens an item shop. At different points in the game, he finds new items. He can sell you a Lucky Jewel, Mystery Egg, and Frying Pan. The Frying Pan may sound useless, but it's actually Toadstool's best weapon.
Credit goes to: http://www.rpgclassics.com/shrines/snes/smrpg/secrets.shtml