In the house that I grew up in, for whatever dumb reason the light switch for the main bathroom was on the outside of the door (my brothers and I used to love switching the lights off on my sister while she was in the shower). We sold that house over 10 years ago and I’ve lived in about 6 others since then but to this day whenever I go into a bathroom I instinctively put my hand on the outside door frame to flick on the lights on the non-existent light switch.