Prior to starting school, I thought the classroom was called a "glassroom", so I pictured a room inside a giant drinking glass.
I also thought the rag and bone men were coming to abduct me for some reason, I was terrified of them.
Also, I was told that the angel on top of the Christmas tree was alive, and on Christmas Eve she'd grow big and help Santa when he brought the presents. I think this was meant to be a nice idea, but I'd look at the angel's eyes and be convinced they followed me when I moved.