This was actually more recently than childhood, but until I looked up the lyrics to "Absolutely (Story Of A Girl)" by Nine Days, I was wondering why on Earth they were singing "When you look in the mirror, say hi to your shoes"... (They were really saying "So how do you choose?")
A childhood belief about misheard lyrics

others believed things like this
- I used to believe the word shoes was spelled shouse. It looked right to me... — Shouse
- When I was younger, I saw Madonna's video for "Material Girl". I thought she was singing "I'm a Cheerio Girl"!— Greg
- I used to believe that there was a person in the mirror who looked exactly like meAnon
- I used to think that if I looked in a mirror for over 5 mins I would dissapere to Narnia!— Quako
- I believed that if I looked too long in the mirror admiring myself the Devil would appear.— Paul Elletson
- When I looked up in the sky and could see the clouds moving I used to think that it was the earth spinning.— JOhn