Go to Nimbus land and into the castle. Now, go to the room with the Guard walking around the huge potted plant. To get there, go forward, left, forward on the red flooring, and then through the leftmost door. Now, most characters in this game are programmed so that they stop when Mario stands in front of them. However, when blocking this character's path, he will try to continue moving in it. So, you can block his way and force him in certain directions. Apparently, boundaries weren't programmed onto him, so you can force him out of the boundaries of the area, into the wall, into the pot - basically anywhere!
Submitted by: Glitched Symbols