At the end of world 1-7 are a few red and yellow bridges which, if Yoshi ground-pounds, will break into pieces and fall into the water. If you pause the game after Yoshi breaks the bridge and before he hits the water, Yoshi and the bridge pieces will continue to fall, even though the game is paused. Keep it paused for a few seconds and you'll witness pieces of the bridge falling from the top of the screen, but all action will stop before long. Anyway, if you unpause after Yoshi drops under the water, the game will think Yoshi fell off a cliff, and Yoshi will lose a life.

This does not work in the original Super Mario World 2: Yoshi's Island because the pause screen is different.