1. If you're persistent enough (or use speed hacks to counteract the movement slowdown) you can repeatedly loop through the doorway that shrinks you on the dark side. Doing so gradually clips the camera into the floor.
You can't do this on the light side, since there are stairs in the way that prevent you from passing because you get to small to jump up them.2. Some stairs in this area can't be walked up
3. Bringing a cube across this seam converts it to an alternate cube sometimes.