This is a helpful glitch in Super Mario 64 DS. Go to Whomp's Fortress as Mario or Luigi (or someone with their caps) on a star after star 2, and head over next to the lower thwomp. There will be 2 orange boxes. Punch the back one, and you will get a super mushroom. Now, go into the back corner (the one with the warp). You will reappear near the top. Jump over the fence, then get a running start, then jump and hold B, aiming for the top ledge. If done right, you should hang on. Pull yourself up, and touch the board that is nearby. It falls over. As long as you stand on it or touch it, your lives should start shooting up out of control! Unfortunately, the counter stops at 100.
NOTE: This glitch is semi-hard to pull off.
This glitch was found on a GameFAQs FAQ.