I'm 44 years old and I still can't stand people standing behind me if I'm sitting down. When I was a kid and I did something wrong my dad would sit me at the table while he walked around yelling at me and every so often he would walk behind me and slap the back of my head.
To this day I still get so uncomfortable that I have to get up or ask the person to move. Even if it's my own kids, I can't stand it.