In the song "Jingle Bells" I thought the lyric "one horse open sleigh" was "one horse soapin sleigh." For years I wondered what the heck a "soapin sleigh" was. I figured that maybe they added soap to the bottom of the sleigh to help it move along? I don't think I figured it out until I was in my late 20s.
A childhood belief about songs

others believed things like this
- I used to think the song "Walk this way" by Arosmith went horse and sleigh insted of singing walk this way.— Derek
- I used to believe that unicorns were real creatures. I thought they were just another type of horse.Anon
- a donkey is just a small horse.Anon
- I used to think that beer was horse pee. Probably because that's what my mom told me...— Kara
- When I was three I used to believe that cow and horse are wife and husband.— xenia
- I used to think giraffes were a type of horse— Crocotta1