Wow.

I'm surprised I've never come across that before. There are a lot of glitches in MM2 you can check out -- I'm sure you can find them easily enough on Youtube. The only one I remember is using Item-1 in the battle against Bubble Man in Bubble Man's stage, you skip to some glitched out version of one of the Wily's Fortress levels.
There's also that.

I've considered buying a Famicom so that I can play some of the wicked-awesome Japanese releases that they have out there, but I haven't gotten around to it yet.