In Chocolate Island 3, bring Yoshi to the first Goal. Get on the block that has the vine, jump up, then jump off Yoshi. Just like the misplaced keyhole bug, you want to get on the goal platform without the screen scrolling up. Next, go through the goal. When the course clear iris-out effect focuses in on the bottom of the screen, the screen will flicker, or turn black and freeze up. If the game didn't freeze, you'll go back to the map screen like normal, except the colors will be messed up. The next time you enter a level, the colors will be back to normal, but you'll have several black vertical lines in the background. Reset the SNES to get the game back to normal.
WARNING: We have witnessed this glitch erase all saved games. Experiment at your own risk.