After you get 120 stars, go the the cannon outside. Aim at the rightmost tip of the cloud to the left of the castle(It's high in the sky). If you aimed right, you'll land in the Vanishing cap hole.
In the Vanishing cap place, bring your energy down to two pieces. Then get lit on fire by one of those black things and run off the edge. When you appear in the moat, you drown.
After you get 120 stars, shoot onto the castle roof. Go by the cone shaped thing on the right side of the roof and go to the corner of the castle roof. Try to get on the very corner. then fall off, but grab the edge of the roof. Pull yourself back up, and Mario will lose his hat and die.
I'll let everybody else post the other glitches...
Hamster Sauce!