runouw.com

Just discovered this.
So by holding Down in the 1st red circled area and holding left or right, I end up in a COMPLETELY DIFFERENT TRANSITION, which is the other red circled area.

What I think is happening is that Mario is going through these blocks, and then up to the nearest possible ground in the next transition. I'm not sure how it could be used, other than maybe some sort of secret area.

I know what you're talking about, because this bothered me in one of my levels. I find it happens when you un-crouch at the closest point towards the ceiling before getting pushed through the platform.