Until I was about 8, I though my parents were calling an emergency vehicle "ambiliance" instead of ambulance, my nickname being Billy and my parents' mid-western pronunciation adding to the confusion.
A childhood belief about speaking

others believed things like this
- Ironically my parents were born on the same day; so growing up, I thought all parents had the same birthdays. Anon
- I used to think that if you met your parents' boss, your parents would be fired!! AAAAAHHHHHHH!!!— Spoot
- My mom thought "ambulance" was "ambliance"— Molly
- Our mum told us that the ice-cream van noise was a children's ambulance— moonpants & sausage
- I used to believe that adding salt to food will make it cooler.— Ale Nijamkin
- I thought Jack was a nickname for Jackery ( like Zack and Zachary).— Bootlebat