While visiting family in Italy at age 6, I asked my mom what the bowl next to the toilet was for. She told me it was a water fountain. When I proceeded to lean over to take a drink, she about tackled me. It wasn't until many years later that I discovered it was a bidet for washing your privates.
A childhood belief about bathrooms

others believed things like this
- To clean the goldfish you put washing up liquid into its bowl.— Sev
- Until about 6 months ago (I'm 21), I believed a bidet was used to wash your feet in.
Eep!— Rebekah - I used to believe that toilet seats were for kids only and that adults sat directly on the bowl. — Evan Klyne
- I thought tonic water was toxic water and wondered why would anyone drink it if it is toxic?— Dr.Badguy
- I used to think that bleaching your hair meant washing your hair with toilet bleach.Anon
- I used to believe that if I flushed the toilet before I showered, I would take a shower in dirty toilet water.— Chris D