First off,this cheat is for super mario 64 for nintendo64.second,i will explain the glitch.

to do this,u must defeat the first bowser and go to the basement.then go to the small hallway and go through the door.go left from there and there should be a Toad by a pillar.jump above the toad(closer to the pillar)and ground pound.if done correctly,u will be behind the toad and in the pillar.u cant move around,except if u get out.it is not really a helpful glitch,but its always fun to see strange stuff thats not supposed to happen in your everyday life.