Several years ago, I found something quite weird. When I swam toward the drainage area at my estate, I was able to look below the estate. When I pressed page down, I saw something quite weird: an upside-down moon. While I was surprised, I brushed off the incident.
Eventually, I searched online one day when the event crossed my mind. It turns out other people had seen the moon too, and there was even a method to see it up-close. On December 2nd, 2011, I went and saw it for myself.
First, you need to do the invisible staircase glitch in the shallow pond at your estate. Then, you must walk below the estate. At this point, you should start swimming in an invisible lake below the estate. Swim east for a little while, and you should see the moon.
It's nothing too serious, and to this day, I'm not sure whether it was a slip-up or an Easter Egg.