I thought it was "all of THE sudden" instead of "all of A sudden." I was like past high school when I found out and I still cannot stop saying it my way! I can't even write it--I use "suddenly" instead!
A childhood belief about speaking

others believed things like this
- I used to believe in a sudden end of the world— anoni
- My teacher held out a hand to say, "stop" but I thought she wanted a high-five.Anon
- I thought that wars had to last four years... just like high school and college.— A. Falk
- Until I was in High School, I really thought that the "underground railroad" was under the ground.— S
- Until junior high school, I thought Monty Python was a wrestler.— Jamie
- I used to believe that you got married right after you finished high school or college. Anon