I agree, going to the bathroom on psychedelics is always weird. It's an enclosed space, often white, and often with a patterned tile floor. And it's quiet. So it makes sense to me that it would be bizarre. The last time I dropped acid, I didn't realized how much I was tripping until I went to the bathroom. I was with a group of friends and they were being very chatty, so it was especially weird to suddenly be plunged into complete silence. The walls were white, but they looked like they had a shifting pattern, and they seemed to be breathing.
Bathrooms on DXM always freak me out, though. Looking in the mirror is always a bad move. My eyes look vacant and far-away, and I look alien to myself. It's unsettling as fuck.