For the first decade or so of my life, I believed that mayo and mayonaise were different foods. I had heard of mayo but not in reference to what it actually is, so I pictured it as brown goop (as opposed to white-ish yellow goop).
A childhood belief about general

others believed things like this
- I used to think mayo was sandwich glue and u had to have it to keep it togetherAnon
- I used to believe that white people had white poop and that mine was brown because I was brownAnon
- I believed until I was 18 that if I got tuna in the mayonaise jar, I would die the next time I ate it. — Sue
- as a young child i thought poo was brown from eating chocolate and pee was yellow from drinking apple juice!Anon
- when I was little I used to think that white people had pink poop (i am brown so my poop is brown)— helena muteka
- I used to believe that if white people would turn brown in the sun then brown people would turn white.Anon