Zelda II: The Adventure of Link/Cheats

Pass on the experience
After Link deposits a crystal in the statue, he automatically begins to rise to the next level of experience. When this occurs, you can pause the game, and quick exit to the save screen (press on the second controller) and select another file. The file that you select will begin to accumulate the amount of experience that the Link who deposited the crystal should have received. In this way, you can cause another file to rise very quickly in levels beyond where he would normally be.

Credits and sources
Codes found by GameGenie.com