Lucky 7,777 Gold
Farm gold from enemies, if your gold reaches 777, you will automatically be rewarded with an additional 7000 gold.
Maximum life drops
At the start of the game, enter the first house. Go down the rope and enter the door. Talk to the old women on the right, she will give you a chest of 5 lifedrops. DO NOT OPEN THE CHEST. Instead, keep talking to her for at least 20 times. She will now dropped 20 chest, 100 lifedrops. Open them all to max out your blue hearts. Once you open one of her chests, you can no longer get anymore by talking to her.
Sound Test Menu
To open the hidden sound test menu, at the title screen when New Game is selected. Press up, down, up, down, left, left, right, right. There is 53 sounds in total, press up/down to select them, and Start button to hear them.