I found a special spot in trying to mess up Mario 3 by accessing weird glitched levels! There is a strange castle where the background is destroyed and you need the swim in air code to get around and explore the level. You cannot exit the level. There are baddies from the castle here including a ghost that follows you around.
Then there are the 2 glitched hammer bros levels. One has castle music and water but does not go anywhere, you cannot exit. The other one is a strange hammer bros level that you can further explore as in it's not just one frame. It' s really weird and glitched out..the coin boxes remind me of the glitched castle stage. You can exit by going into a pipe! It's so strange!!
I am hoping I can find some more glitch levels..it is difficult to do and even more hard to find a good interesting one. I will explore my randomized hack of Mario 3 as it seems to give you different glitch stages when you find them.