I used to believe that the song "I Shot The Sheriff" went "I shot Sherry, but I didn't shoot the rest of 'em." Then I learned that it was "I Shot The Sheriff," and then decided that it went "I shot the sheriff, but I didn't shoot the President." I only learned the true lyrics a few months ago!!!
A childhood belief about misheard lyrics

others believed things like this
- I used to believe that guns shot out blood because everytime somebody shot a gun in a movie you saw blood.Anon
- I used to believe because I was born I Abe Lincoln's birthday I had a better shot at being President.— END
- I thought that my Sheriff Woody doll could protect me if I was home alone.Anon
- i used to think in the song "hit me with your best shot" was really "hit me while i'm on pot" yea.... i suck!!— Donna
- I thought the song "Hit me with your best shot" was "Hit me with your pet shark"Anon
- I used to believe that when you were fired, you were shot.— Murray