When we were little our parents put us in the bath together to save on the hot water. We used to stir up the water with bubble bath in it to make more bubbles, which was good fun. However, my big sister convinced me that to play this game I had to have my eyes closed and my mouth open. If I started stirring without closing my eyes and opening my mouth she would say "Remember, Eyes Closed, Mouth Open!" and if I still didn't obey she would do it herself to remind me of my duty. I noticed at the time that while I was doing Eyes Closed, Mouth Open I used to get a lot of water in my mouth, but after all, we were stirring and there was water flying around - that was only to be expected. I didn't learn until I grew up that Eyes Closed, Mouth Open was invented entirely so that she could throw water into my mouth without me seeing.
Also at a country park near our house where we often went there was a miniature railway leading to a model "fairy village". We loved to ride on it, but one day my sister announced "You have to do Eyes Closed, Mouth Open or you won't see the fairies!" And like a fool, I obeyed. I don't think she put anything in my mouth that time, though. :-)
A childhood belief about bathrooms

others believed things like this
- my brother told me that if i ride my bike with my mouth open i will swallow my tounge. Anon
- I used to think wall outlets looked like little faces (eyes and mouth), and so I would talk to them sometimes!— EJ
- I used to believe that if I slept with my mouth open that spiders would crawl in there and live in my stomachAnon
- My sister used to think that nobody could see her if she closed her eyes.— Dave
- When I was little my friend told me that if you snease with your eyes open you eyes will fall out!Anon
- I was born brunette with brown eyes and dark hair, i thought people with blue eyes, had water in them.Anon