I was able to find another strange level on Mario 3!! Have been using the game genie to mess up the game and find weird levels using codes that 'switch' the stages with different ones. Most times it blacks out or resets but there are a few I found that have glitch stages.
When I first started this weird castle level you are trapped underneath the ground but I used the swim in air code to move to the other end of the stage. Then used a code to pull bricks out of anywhere. I was able to open a gap and get through the level back to the beginning. Had to open a hole to get back into it at the wall with a door on it. When you try to go through the door the game just freezes. You are able to exit this stage through a pipe closer to the beginning.
Then there is another strange level where you drop into a mishmash of random objects like note blocks. Here Mario got stuck!!
I have a few more Mario 3 Glitch levels to show! Although there are not that many and some of them are mostly empty so I was glad to find some that are sort of interesting and weird.